SCIENCE 1G - Moodle PDF

The structure of the earth is divided into four major components: the crust, the mantle, the outer core, and the inner core. Each layer has a unique chemical composition, physical state, and can impact life on Earth's surface. Movement in the mantle caused by variations in heat from the core, cause...

The structure of the earth is divided into four major components: the crust, the mantle, the outer core, and the inner core. Each layer has a unique chemical composition, physical state, and can impact life on Earth's surface. Movement in the mantle caused by variations in heat from the core, cause the plates to shift, which can cause earthquakes and volcanic eruptions. These natural hazards then change our landscape, and in some cases, threaten lives and property. Crust: 6 - 50km Crust, the upper layer of the Earth, is not always the same. Crust under the oceans is only about 5 km thick while continental crust can be up to 65 km thick. Also, ocean crust is made of denser minerals than continental crust. There are two types of Crust: Continental crust The continental crust is the layer of granitic, sedimentary and metamorphic rocks which form the continents and the areas of shallow seabed close to their shores, known as continental shelves. It is less dense than the material of the Earth's mantle and thus "floats" on top of it. Oceanic Crust Oceanic crust is the uppermost layer of the oceanic portion of a tectonic plate. It is composed of the upper oceanic crust, with pillow lavas and a dike complex, and the lower oceanic crust, composed of troctolite, gabbro and ultramafic cumulates. Beneath the crust is the mantle, which is also mostly solid rocks and minerals, but punctuated by malleable areas of semi-solid magma. At the center of the Earth is a hot, dense metal core. Mantle: 2900 km The Earth's mantle is a layer of silicate rock between the crust and the outer core. Its mass of 4.01 × 1024 kg is 67% the mass of the Earth. It has a thickness of 2,900 kilometres (1,800 mi) making up about 84% of Earth's volume. It is predominantly solid but in geological time it behaves as a viscous fluid. Partial melting of the mantle at mid-ocean ridges produces oceanic crust, and partial melting of the mantle at subduction zones produces continental crust. The mantle is the mostly-solid bulk of Earth's interior. The mantle lies between Earth's dense, super-heated core and its thin outer layer, the crust. The mantle is about 2,900 kilometers (1,802 miles) thick, and makes up a whopping 84% of Earth's total volume. Upper Mantle (soft): 370 km The upper mantle is not uniform throughout. The topmost, thin layer of it is very similar to the Earth's crust. Together with the crust, we call it the lithosphere. Below the lithosphere is a layer of upper mantle called the asthenosphere. Upper mantle material which has come up onto the surface is made up of about 55% olivine and 35% pyroxene and 5 to 10% of calcium oxide and aluminum oxide. The upper mantle is dominantly peridotite, composed primarily of variable proportions of the minerals olivine, clinopyroxene, orthopyroxene, and an aluminous phase. Transitional Zone: 600 km Lower Mantle (solid): 1700 km The rest of the mantle between the Upper Mantle and the Outer Core is known as the Lower Mantle. It is denser and hotter than the Upper Mantle. The Lower Mantle is more solid than the Upper Mantle Composition: Olivine, magnesium, iron Outer Core (liquid): 2100 km The outer core is the third layer of the Earth. It is the only liquid layer, and is mainly made up of the metals iron and nickel, as well as small amounts of other substances. The outer core is responsible for Earth's magnetic field. As Earth spins on its axis, the iron inside the liquid outer core moves around. The Outer Core is the second to last layer of the Earth. It is a magma like liquid layer that surrounds the Inner Core and creates Earth's magnetic field. In this section you will learn about how Earth's magnetic field is created, how hot it is, how thick the Outer Core is and a few interesting facts about the Outer Core. Temperature: about 4000-5000 degrees Celsius. The Inner Core is so hot it causes all the metal in the Outer Core to melt into liquid magma. Composition: iron and some nickel. There is very few rocks and iron and nickel ore left in the Outer Core because of the Inner Core melting all the metal into liquid magma Thickness: about 2200 km thick. It is the second largest layer and made entirely out of liquid magma. Magnetism: Because the outer core moves around the inner core, Earth's magnetism is created. Inner Core (solid): 1350 km The planet Earth consists of a series of distinct layers, each of which has a unique structure. The top layer, known as the crust, is the thinnest layer of the Earth with a thickness of 30 km (18.6 miles). Below the crust, there are four distinct layers and these are called the upper mantle, lower mantle, outer core and inner core. The inner core of the Earth has a number of surprising properties. The Earth's inner core is surprisingly large, measuring 2,440 km (1,516 miles) across. It makes up 19 percent of the Earth's total volume, which makes it just 30 percent smaller than the moon. The temperature of the inner core is estimated to be between 3,000 and 5,000 Kelvins (4,940 to 8,540 degrees Fahrenheit). The high temperature comes from three main sources. There is residual heat left from the Earth's formation, and heat is generated by gravitational forces from the sun and moon as they tug and pull on the inner core. Finally, the radioactive decay of elements deep within the Earth also produces heat. Scientists believe that the Earth's inner core is a solid and is mainly composed of iron. The scorching hot iron inner core is able to remain solid because of the extremely high pressures at the center of the Earth. Other elements found in the core include nickel, a metal similar to iron, and silicon, an abundant substance used in glass and computer chips. You'll also find radioactive elements such as uranium and potassium, which give off energy that heats the core. Experiments reported in July 1997 suggest that the inner core spins at a slightly faster speed than the Earth itself. The research conducted at Columbia University suggests that the inner core rotates in the same direction as the rest of the planet. However, the research shows that it makes one complete revolution two-thirds of a second faster than the rest of the planet. Because the Earth's inner core is a solid lump of iron, you may think that it is the source of the Earth's magnetic field. But this is not the case. The Earth's outer core, which consists of molten iron and nickel, flows around the inner core, and this motion produces the magnetic field. What is Continental Drift Theory The continental drift hypothesis was developed in the early part of the 20th century, mostly by Alfred Wegener. Wegener said that continents move around on Earth’s surface and that they were once joined together as a single supercontinent. While Wegener was alive, scientists did not believe that the continents could move.Find a map of the continents and cut each one out. Better yet, use a map where the edges of the continents show the continental shelf. That’s the true size and shape of a continent and many can be pieced together like a puzzle. The easiest link is between the eastern Americas and western Africa and Europe, but the rest can fit together too. Alfred Wegener proposed that the continents were once united into a single supercontinent named Pangaea, meaning all earth in ancient Greek. He suggested that Pangaea broke up long ago and that the continents then moved to their current positions. He called his hypothesis continental drift. Causes of Continental Drift The causes of continental drift are perfectly explained by the plate tectonic theory. The earth’s outer shell is composed of plates that move a little bit every year. Heat coming from the interior of the earth triggers this movement to occur through convection currents inside the mantle. Over the course of millions of year ago, this gradual movement caused the once combined supercontinent to separate into 7 continents you witness in the present day. Almost all plate movement occurs in boundaries which lie between different plates. When plates drift away from each other, there is formation of new crust at divergent boundaries. On the other hand, tectonic movement destroys crust during interaction of the plates. Destruction happens when one plate moves below the other at convergent boundaries. However, the crust is never destroyed when plates move past one another horizontally at transform boundaries. Evidence that support Wegener's Theory Alfred Wegener collected diverse pieces of evidence to support his theory, including geological “fit” and fossil evidence. It is important to know that the following specific fossil evidence was not brought up by Wegener to support his theory. Wegener himself did not collect the fossils but he called attention to the idea of using these scientific documents stating there were fossils of species present in separate continents in order to support his claim. Geological “fit” evidence is the matching of large-scale geological features on different continents. It has been noted that the coastlines of South America and West Africa seem to match up, however more particularly the terrains of separate continents conform as well. Examples include: the Appalachian Mountains of eastern North America linked with the Scottish Highlands, the familiar rock strata of the Karroo system of South Africa matched correctly with the Santa Catarina system in Brazil, and the Brazil and Ghana mountain ranges agreeing over the Atlantic Ocean. Another important piece of evidence in the Continental Drift theory is the fossil relevance. There are various examples of fossils found on separate continents and in no other regions. This indicates that these continents had to be once joined together because the extensive oceans between these land masses act as a type of barrier for fossil transfer. Four fossil examples include: the Mesosaurus, Cynognathus, Lystrosaurus, and Glossopteris. The Mesosaurus is known to have been a type of reptile, similar to the modern crocodile, which propelled itself through water with its long hind legs and limber tail. It lived during the early Permian period (286 to 258 million years ago) and its remains are found solely in South Africa and Eastern South America. Now if the continents were in still their present positions, there is no possibility that the Mesosaurus would have the capability to swim across such a large body of ocean as the Atlantic because it was a coastal animal. The now extinct Cynognathus, which translates to “dog jaw”, was a mammal- like reptile. Roaming the terrains during the Triassic period (250 to 240 million years ago), the Cynognathus was as large as a modern wolf. Its fossils are found only in South Africa and South America. As a land dominant species, the Cynognathus would not have been capable of migrating across the Atlantic. The Lystrosaurus, which translates to “shovel reptile,” is thought to have been an herbivore with a stout build like a pig. It is approximated that it grew up to one meter in length and was relatively dominant on land during the early Triassic period (250 million years ago). Lystrosaurus fossils are only found in Antarctica, India, and South Africa. Similar to the land dwelling Cynognathus, the Lystrosaurus would have not had the swimming capability to traverse any ocean. Possibly the most important fossil evidence found is the plant, Glossopteris. Known as a woody, seed bearing tree, the Glossopteris is named after the Greek description for tongue due to its tongue shaped leaves and is the largest genus of the extinct descendant of seed ferns. Reaching as tall as 30 meters, the Glossopteris emerged during the early Permian period (299 million years ago) and became the dominant land plant species until the end of the Permian. The Glossopteris fossil is found in Australia, Antarctica, India, South Africa, and South America—all the southern continents. Now, the Glossopteris seed is known to be large and bulky and therefore could not have drifted or flown across the oceans to a separate continent. Therefore, the continents must have been joined at least one point in time in order to maintain the Glossopteris’ wide range across the southern continents. If the continents of the Southern Hemisphere are put together, the distribution of these four fossil types form continuous patterns across continental boundaries. Of course, possible explanations are brought to attention. One explanation is the species could have migrated via a land bridge or swam to the other continents. However, a land bridge is not applicable due to the differences in densities between the continents and oceans floor and violation of the isostasy concept. Moreover, swimming as a possibility is foolish due to the lack of formidable swimming capabilities to travel across such an extensive body of water like the Atlantic. An additional resolution is that the species could have merely evolved separately on the other continents. History of the Theory of Plate Tectonics The theory of plate tectonics, like every scientific theory, resulted from centuries of observations and compilation of many scientists’ works. It started as a hypothesis and had to be proven with hard evidence before being completely accepted by the scientific community. Nonetheless, we consider Alfred Wegener, a meteorologist of the beginning of the 20th century, as the father of the theory that he at that time referred to as “the continental drift”. His book The Origin of Continents and Oceans, published in 1915, is widely accepted as the beginning of modern plate tectonics, even if the theory was only widely accepted in a refined version in the 1960s. The main idea that Wegener and others had was that modern continents formed a single landmass in the past. This idea was supported by simple observations like the fact that South-American and African coastlines fit so well, or that we can find the same fossils in similar sedimentary rocks on both continents. The theory needed an explanation for continental drift, a process that would account for the motion of tectonic plates. The continental drift was strongly criticised during the first half of the 20th century, until the second world war. During the war, the latest radar technology was used to map the seafloor. Rapidly, evidence pointing to the process of seafloor spreading and effective plate motion was accumulated. After the war, marine geology was developed, which led to the discovery of the subduction process under the continental margins. Subduction was a perfect way to balance the extension observed at the mid-ocean ridges by recycling oceanic lithosphere in the mantle. Plate tectonics theory then became widely accepted among scientists because it relied on hard evidence and could explain most of the modern geological structures such as ocean basins, mountain ranges, and rifts. What is Pangea Pangea, also spelled Pangaea, in early geologic time, a supercontinent that incorporated almost all the landmasses on Earth. Supercontinent A supercontinent is a landmass made up of most or all of Earth’s land. By this definition the landmass formed by present-day Africa and Eurasia could be considered a supercontinent. The most recent supercontinent to incorporate all of Earth’s major—and perhaps best-known—landmasses was Pangea. Supercontinents have coalesced and broken apart episodically over the course of Earth’s geological history. Scientists suggest that the next supercontinent capable of rivaling Pangea in size will form some 250 million years from now, when Africa, the Americas, and Eurasia collide. How did it formed It’s now widely accepted that the formation of supercontinents like Pangea can be explained by plate tectonics—the scientific theory which states that Earth’s surface is made up of a system of plates that float on top of a deeper plastic layer. Earth’s tectonic plates collide with and dive beneath one another at convergent boundaries, pull away from one another at divergent boundaries, and shift laterally past one another at transform boundaries. Continents combine to form supercontinents like Pangea every 300 to 500 million years before splitting apart again. Many geologists argue that continents merge as an ocean (such as the Atlantic Ocean) widens, spreading at divergent boundaries. Over time, as the landmasses collide in the limited space remaining, a Pangea-sized supercontinent forms. What is seafloor spreading Seafloor Bathymetry World War II gave scientists the tools to find the mechanism for continental drift that had eluded Wegener. Maps and other data gathered during the war allowed scientists to develop the seafloor spreading hypothesis. This hypothesis traces oceanic crust from its origin at a mid-ocean ridge to its destruction at a deep sea trench and is the mechanism for continental drift.During World War II, battleships and submarines carried echo sounders to locate enemy submarines. Echo sounders produce sound waves that travel outward in all directions, bounce off the nearest object, and then return to the ship. By knowing the speed of sound in seawater, scientists calculate the distance to the object based on the time it takes for the wave to make a round-trip. During the war, most of the sound waves ricocheted off the ocean bottom. This animation shows how sound waves are used to create pictures of the seafloor and ocean crust.After the war, scientists pieced together the ocean depths to produce bathymetric maps, which reveal the features of the ocean floor as if the water were taken away. Even scientist were amazed that the seafloor was not completely flat. What was discovered was a large chain of mountains along the deep seafloor, called mid-ocean ridges. Scientists also discovered deep sea trenches along the edges of continents or in the sea near chains of active volcanoes. Finally, large, flat areas called abyssal plains we found. When they first observed these bathymetric maps, scientists wondered what had formed these features. Seafloor Magnetism Sometimes, for reasons unknown, the magnetic poles switch positions. North becomes south and south becomes north. During normal polarity, the north and south poles are aligned as they are now. With reversed polarity, the north and south poles are in the opposite position.During WWII, magnetometers attached to ships to search for submarines located an astonishing feature; the normal and reversed magnetic polarity of seafloor basalts creates a pattern. Stripes of normal polarity and reversed polarity alternate across the ocean bottom. These stripes also forms a mirror image of itself on either side of the mid-ocean ridges. But the stripes end abruptly at the edges of continents, sometimes at a deep sea trench. The characteristics of the rocks and sediments change with distance from the ridge axis as seen in the Table below. Seafloor Spreading Hypothesis Scientists brought these observations together in the early 1960s to create the seafloor spreading hypothesis. In this hypothesis, hot buoyant mantle rises up a mid-ocean ridge, causing the ridge to rise upward. The hot magma at the ridge erupts as lava that forms new seafloor. When the lava cools, the magnetite crystals take on the current magnetic polarity and as more lava erupts, it pushes the seafloor horizontally away from ridge axis.The magnetic stripes continue across the seafloor. As oceanic crust forms and spreads, moving away from the ridge crest, it pushes the continent away from the ridge axis. If the oceanic crust reaches a deep sea trench, it sinks into the trench and is lost into the mantle. Scientists now know that the oldest crust is coldest and lies deepest in the ocean because it is less buoyant than the hot new crust.Seafloor spreading is the mechanism for Wegener’s drifting continents. Convection currents within the mantle take the continents on a conveyor-belt ride of oceanic crust that over millions of years takes them around the planet’s surface. Seafloor Magnetic Striping The specific magnetism of basalt rock is determined by the Earth's magnetic field when the magma is cooling. Scientists determined that the same process formed the perfectly symmetrical stripes on both side of a mid-ocean ridge. The continual process of seafloor spreading separated the stripes in an orderly pattern. What is Plate Tectonic From the deepest ocean trench to the tallest mountain, plate tectonics explains the features and movement of Earth's surface in the present and the past. Plate tectonics is the theory that Earth's outer shell is divided into several plates that glide over the mantle, the rocky inner layer above the core. The plates act like a hard and rigid shell compared to Earth's mantle. This strong outer layer is called the lithosphere, which is 100 km (60 miles) thick, according to Encyclopedia Britannica. The lithosphere includes the crust and outer part of the mantle. Below the lithosphere is the asthenosphere, which is malleable or partially malleable, allowing the lithosphere to move around. How it moves around is an evolving idea. History developed from the 1950s through the 1970s, plate tectonics is the modern version of continental drift, a theory first proposed by scientist Alfred Wegener in 1912. Wegener didn't have an explanation for how continents could move around the planet, but researchers do now. Plate tectonics is the unifying theory of geology, said Nicholas van der Elst, a seismologist at Columbia University's Lamont-Doherty Earth Observatory in Palisades, New York. "Before plate tectonics, people had to come up with explanations of the geologic features in their region that were unique to that particular region," Van der Elst said. "Plate tectonics unified all these descriptions and said that you should be able to describe all geologic features as though driven by the relative motion of these tectonic plates." Plate Boundaries Categorization of plate boundaries is based off of how two plates move relative to each other. There are essentially three types of plate boundaries, which are divergent, convergent, and transform. In the case of divergent plate boundaries, two of earth’s plates move away from each other. Spreading centers and areas where new ocean floor are generally located at divergent plate boundaries. An example of a divergent plate boundary is the Mid-Atlantic Ridge. Depending on what type of lithospheric crust each diverging plate is, whether oceanic or continental, varying geographic features are formed. For example, when two continental plates diverge from each other, an ocean basin is created due to the separation of land. On the other hand, if two oceanic plates diverged, a mid ocean ridge would form, which is also known as a spreading center. Divergent plate boundaries are commonly associated with shallow earthquakes. What are the different types of plate tectonic boundaries? There are three kinds of plate tectonic boundaries: divergent, convergent, and transform plate boundaries. The Earth’s lithosphere, which includes the crust and upper mantle, is made up of a series of pieces, or tectonic plates, that move slowly over time. A divergent boundary occurs when two tectonic plates move away from each other. Along these boundaries, earthquakes are common and magma (molten rock) rises from the Earth’s mantle to the surface, solidifying to create new oceanic crust. When two plates come together, it is known as a convergent boundary. The impact of the colliding plates can cause the edges of one or both plates to buckle up into a mountain ranges or one of the plates may bend down into a deep seafloor trench. A chain of volcanoes often forms parallel to convergent plate boundaries and powerful earthquakes are common along these boundaries. At convergent plate boundaries, oceanic crust is often forced down into the mantle where it begins to melt. Magma rises into and through the other plate, solidifying into granite, the rock that makes up the continents. Thus, at convergent boundaries, continental crust is created and oceanic crust is destroyed. Two plates sliding past each other forms a transform plate boundary. Natural or human-made structures that cross a transform boundary are offset—split into pieces and carried in opposite directions. Rocks that line the boundary are pulverized as the plates grind along, creating a linear fault valley or undersea canyon. Earthquakes are common along these faults. In contrast to convergent and divergent boundaries, crust is cracked and broken at transform margins, but is not created or destroyed. Causes of Divergent Boundary A tectonic boundary where two plates are moving away from each other and new crust is forming from magma that rises to the Earth's surface between the two plates. The middle of the Red Sea and the mid-ocean ridge (running the length of the Atlantic Ocean) are divergent plate boundaries. Examples of Divergent Boundary The mid-Atlantic ridge is an example of a divergent boundary, where the Eurasian Plate that covers all of Europe separates from the North American Plate. This underwater mountain range is constantly growing as new crust is formed Features Exactly what happens when two plates diverge depends on the two types of plates involved: oceanic plates and continental plates. Oceanic plates are, unsurprisingly, plates below sea level and under the oceans. But the 'oceans' part isn't actually what makes it an oceanic plate because there are some exceptions to this rule. Instead, it's more about the plate's composition. Oceanic plates are composed of mafic or basaltic rock. Continental plates are indeed above sea level, but again, what makes a plate officially continental is the presence of felsic or granitic rock. Most divergent boundaries in the world today are between two oceanic plates. When these plates separate, the magma rushes up to fill the gap and creates underwater volcanoes. This is the creation of brand new crust! This crust can remain deep under the oceans, creating underwater ridges, or it can rise to the surface over time to form islands. When two continental plates separate, it is theoretically possible for a similar thing to happen; volcanoes could form to create new crust. However, continental plates are far thicker than oceanic ones. Because of this, what usually happens instead is that a continent will gradually break apart, as water from the sea rushes in to fill the gap. By the time magma has a gap to fill, that gap is already deep underwater in a brand new ocean. This starts out as an enormous rift valley across the land, until that valley fills with water. When one continental and one oceanic plate diverge, there can be features of both. It is more a matter of whether the boundary itself lies over an ocean or land than whether the plates are continental or oceanic. Convergent Boundary When continental and oceanic plates collide, the thinner and more dense oceanic plate is overridden by the thicker and less dense continental plate. The oceanic plate is forced down into the mantle in a process known as "subduction." As the oceanic plate descends, it is forced into higher temperature environments. At a depth of about 100 miles (160 km), materials in the subducting plate begin to approach their melting temperatures and a process of partial melting begins. This partial melting produces magma chambers above the subducting oceanic plate. These magma chambers are less dense than the surrounding mantle materials and are buoyant. The buoyant magma chambers begin a slow ascent through the overlying materials, melting and fracturing their way upwards. The size and depth of these magma chambers can be determined by mapping the earthquake activity around them. If a magma chamber rises to the surface without solidifying, the magma will break through in the form of a volcanic eruption. Transform Boundary Transform Plate Boundaries are locations where two plates slide past one another. The fracture zone that forms a transform plate boundary is known as a transform fault. Most transform faults are found in the ocean basin and connect offsets in the mid-ocean ridges. A smaller number connect mid-ocean ridges and subduction zones. Transform faults can be distinguished from the typical strike-slip faults because the sense of movement is in the opposite direction (see illustration). A strike-slip fault is a simple offset; however, a transform fault is formed between two different plates, each moving away from the spreading center of a divergent plate boundary. When you look at the transform fault diagram, imagine the double line as a divergent plate boundary and visualize which way the diverging plates would be moving. A smaller number of transform faults cut continental lithosphere. The most famous example of this is the San Andreas Fault Zone of western North America. The San Andreas connects a divergent boundary in the Gulf of California with the Cascadia subduction zone. Another example of a transform boundary on land is the Alpine Fault of New Zealand. Plate Tectonics Plate Tectonics is the theory supported by a wide range of evidence that considers the earth's crust and upper mantle to be composed of several large, thin, relatively rigid plates that move relative to one another. Slip on faults that define the plate boundaries commonly results in earthquakes. Several styles of faults bound the plates, including thrust faults along which plate material is subducted or consumed in the mantle, oceanic spreading ridges along which new crustal material is produced, and transform faults that accommodate horizontal slip (strike slip) between adjoining plates. What is Tectonic Plate A tectonic plate (also called lithospheric plate) is a massive, irregularly shaped slab of solid rock, generally composed of both continental and oceanic lithosphere. Plate size can vary greatly, from a few hundred to thousands of kilometers across; the Pacific and Antarctic Plates are among the largest. Tectonic plates are pieces of Earth's crust and uppermost mantle, together referred to as the lithosphere. These are (also called lithospheric plates) massive, irregularly shaped slab of solid rock, generally composed of both continental and oceanic lithosphere. Movements of the Plates What happens when plates move? When the plates move, they will eventually collide. These collisions cause earthquakes, tsunamis, and volcanoes. Earthquakes usually happen when two plates slide past each other. Volcanoes form when one plate sinks under the other plate allowing lava/magma to seep through and build up to form a volcano. What causes plate movement? The force that causes most of the plate movement is thermal convection, where heat from the Earth's interior causes currents of hot rising magma and cooler sinking magma to flow, moving the plates of the crust along with them. What really happens when plates move? When the plates move, they will eventually collide. These collisions cause earthquakes, tsunamis, and volcanoes. Earthquakes usually happen when two plates slide past each other. Volcanoes form when one plate sinks under the other plate allowing lava/magma to seep through and build up to form a volcano. What is the force that allows plates to move? Heat and gravity are fundamental to the process The energy source for plate tectonics is Earth's internal heat while the forces moving the plates are the “ridge push” and “slab pull” gravity forces. It was once thought that mantle convection could drive plate motions. What is the result of plate motion? The movement of these tectonic plates is likely caused by convection currents in the molten rock in Earth's mantle below the crust. Earthquakes and volcanoes are the short-term results of this tectonic movement. The long-term result of plate tectonics is the movement of entire continents over millions of years What are the effects of plate tectonic movement? Crustal Tectonic Plates and their movement How the Earth's crust is split into large sections called tectonic plates is described. Their movement and effects at plate boundaries are explained e.g. earthquakes, volcanoes, mountain building, ocean ridges/trenches, subduction (part of the rock cycle). Causes of Plate Movement The force that causes most of the plate movement is thermal convection, where heat from the Earth's interior causes currents of hot rising magma and cooler sinking magma to flow, moving the plates of the crust along with them. Evidence of Plate Tectonics Evidence from fossils, glaciers, and complementary coastlines helps reveal how the plates once fit together. Fossils tell us when and where plants and animals once existed. Some life "rode" on diverging plates, became isolated, and evolved into new species. There is variety of evidence that supports the claims that plate tectonics accounts for (1) the distribution of fossils on different continents, (2) the occurrence of earthquakes, and (3) continental and ocean floor features including mountains, volcanoes, faults, and trenches: The continents fit together almost like puzzle pieces forming Pangaea (one super-continent). Fossils on different continents are similar to fossils on continents that were once connected. When the continents split, different life forms developed. Most continental and oceanic floor features are the result of geological activity and earthquakes along plate boundaries. The exact patterns depend on whether the plates are converging (being pushed together) to create mountains or deep ocean trenches, (diverging) being pulled apart to form new ocean floor at mid-ocean ridges, or sliding past each other along surface faults. Most distributions of rocks within Earth's crust, including minerals, fossil fuels, and energy resources, are a direct result of the history of plate motions and collisions and the corresponding changes in the configurations of the continents and ocean basins. The history is still being written. Continents are continually being shaped and reshaped by competing constructive and destructive geological processes. Continental Shapes Continental landform, any conspicuous topographic feature on the largest land areas of the Earth. (The term landform also can be applied to related features that occur on the floor of the Earth's ocean basins, as, for example, seamounts, mid-oceanic ridges, and submarine Canyons. Continental Shapes. Continental margins are the zones between the ocean basin and the mass of the continent. The continental shelf is the underwater region from the continental margin to the shoreline. Several Physic graphic Features on the Ocean Floor Features of the ocean include the continental shelf, slope, and rise. The ocean floor is called the abyssal plain. Below the ocean floor, there are a few small deeper areas called ocean trenches. Features rising up from the ocean floor include seamounts, volcanic islands and the mid-oceanic ridges and rises. Vocabulary abyssal plain The flat bottom of the ocean floor; the deep ocean floor. continental shelf The shallow, gradually sloping seabed around the edge of a continent. Usually less than 200 meters in depth. The continental shelf can be thought of as the submerged edge of a continent. continental slope The sloped bottom of the ocean that extends from the continental shelf down to the deep ocean bottom. mid ocean ridge Mountain range on the ocean floor where magma upwells and new ocean floor is formed. seamount A mountain rising from the seafloor that does not reach above the surface of the water. Usually formed from volcanoes. trench Deepest areas of the ocean; found where subduction takes place. Seamounts and Guyots are volcanoes that have built up from the ocean floor, sometimes to sea level or above. Guyots are seamounts that have built above sea level. Erosion by waves destroyed the top of the seamount resulting in a flattened shape. A seamount never reaches the surface so it maintains a “volcanic” shape. Features on Ocean floors Other significant features of the ocean floor include aseismic ridges, abyssal hills, and seamounts and guyots. The basins also contain a variable amount of sedimentary fill that is thinnest on the ocean ridges and usually thickest near the continental margins. Age Distribution of the Oceanic Crust The age of the oceanic crust does not go back farther than about 200 million years. Such crust is being formed today at oceanic spreading centres. Many ophiolites are much older than the oldest oceanic crust, demonstrating continuity of the formation processes over hundreds of millions of years. Oceanic Crust The age of the oceanic crust does not go back farther than about 200 million years. Such crust is being formed today at oceanic spreading centres. Many ophiolites are much older than the oldest oceanic crust, demonstrating continuity of the formation processes over hundreds of millions of years. Marine Sediment Thickness Distribution Global ocean sediment thickness and present‐day ocean sediment accumulation rates are analyzed with respect to the age of the underlying ocean crust. Trends in average sediment thickness and present‐day accumulation rate are well fit by cubic polynomials in crustal age for the global ocean and for individual ocean basins. Sediment thickness and accumulation rates are larger in the North and South Atlantic and Indian Oceans compared to the Pacific Ocean, primarily because the anomalous sediment accumulations that followed continental rifting and collision in the Atlantic and Indian Ocean basins are missing in the Pacific Ocean Marine Sediments Thick sediment accumulations dominate the continental margins of the Atlantic and Indian Oceans that are largely missing from the Pacific Ocean. In contrast, the sediments are much thinner within the interior of all of the ocean basins. Deep Ocean Drilling The Deep Sea Drilling Project (DSDP) was an ocean drilling project designed to analyze the ocean floor.... This showed that new oceanic crust was being formed along the plate boundary and then spreading out laterally, providing evidence to support the theory of seafloor spreading and plate tectonics. What Is Seismology? Seismology is the study of earthquakes and seismic waves that move through and around the earth. A seismologist is a scientist who studies earthquakes and seismic waves. What Are Seismic Waves? Seismic waves are the waves of energy caused by the sudden breaking of rock within the earth or an explosion. They are the energy that travels through the earth and is recorded on seismographs. What is a seismic wave in science? A seismic wave is an elastic wave generated by an impulse such as an earthquake or an explosion. Seismic waves may travel either along or near the earth's surface (Rayleigh and Love waves) or through the earth's interior (P and S waves). Seismic waves When an earthquake happens deep underground a crack will start to open on a pre-existing line of weakness in the Earth's brittle crust. This crack will then grow larger and larger, relieving built-up stress as it goes. The speed at which the crack propagates or grows is 2–3 km/sec. Eventually the rupture will cease to grow and will slow down and stop. The size or magnitude of the earthquake depends upon how much the fault has ruptured (the slip) and also the area over which the rupture has occurred. This rupturing process creates elastic waves in the Earth that propagate away from the rupture front at a much faster speed than the rupture propagates, the exact speed depends upon the nature of the wave (a longitudinal or P-wave is faster than a transverse or S-wave), and on the elastic properties of the Earth. As you go deeper into the Earth, the density and pressure increases and so do the velocities of seismic waves. These are the waves of energy caused by the sudden breaking of rock within the earth or an explosion. They are the energy that travels through the Earth and is recorded on seismographs. There are several different kinds of seismic waves, and they all move in different ways. The two main types of waves are body waves and surface waves. These are waves of energy that travel through the core of the Earth or other elastic bodies generated from earthquake, explosion, or some other process that imparts low-frequency acoustic energy. The propagation velocity of the waves depends on the density and elasticity of the medium. Velocity tends to increase with depth, and ranges from approximately 2 to 8 km/s in the Earth’s crust up to 13 km/s in the deep mantle. Various types travel at different velocities. Refraction or reflection of seismic waves is used for research of the Earth’s interior, and artificial vibration to investigate sub-surface structures. What is a seismic wave in science? A seismic wave is an elastic wave generated by an impulse such as an earthquake or an explosion. Seismic waves may travel either along or near the earth's surface (Rayleigh and Love waves) or through the earth's interior (P and S waves). What are the 4 types of seismic waves? Four types of seismic waves| Specifications of all types of seismic waves. P- Waves (Primary waves) S- Waves (Secondary waves) L- Waves (Surface waves) Rayleigh waves. How do you read seismic waves? The P wave will be the first wiggle that is bigger than the rest of the little ones (the microseisms). Because P waves are the fastest seismic waves, they will usually be the first ones that your seismograph records. The next set of seismic waves on your seismogram will be the S waves. Where are seismic waves the most powerful? Seismic waves can be classified into two basic types: body waves which travel through the Earth and surface waves, which travel along the Earth's surface. Those waves that are the most destructive are the surface waves which generally have the strongest vibration. How do we use seismic waves? Seismic waves, the same type of waves used to study earthquakes, are also used to explore deep underground for reservoirs of oil and natural gas. Seismic waves – the same tool used to study earthquakes – are frequently used to search for oil and natural gas deep below Earth's surface. Do seismic waves travel from the epicenter? Every wave has a high point called a crest and a low point called a trough.... S-waves only move through solids. Surface waves travel along the ground, outward from an earthquake's epicenter. Surface waves are the slowest of all seismic waves, traveling at 2.5 km (1.5 miles) per second. How seismic waves affect buildings? Seismic waves have a particular frequency in which they travel at through the ground.... When the seismic wave's frequency corresponds or is similar to the building's natural frequency, resonance occurs and the building will sway very wildly. (Energy gets transferred to the building at great efficiencies.) How strong does an earthquake have to be to collapse a building? Magnitude Earthquake Effects 5.5 to 6.0 Slight damage to buildings and other structures. 6.1 to 6.9 May cause a lot of damage in very populated areas. 7.0 to 7.9 Major earthquake. Serious damage. 8.0 or greater Great earthquake. Can totally destroy communities near the epicenter. 2 more rows Predicting Earthquakes Strange Animal Behavior - stress in the rocks cause tiny hairline fractures to form, the cracking of the rocks evidently emits high pitched sounds and minute vibrations imperceptible to humans but noticeable by many animals Foreshocks - unusual increase in the frequency of small earthquakes before the main shock Changes in water level - porosity increases or decreases with changes in strain Seismic Gaps - based off the chronological distribution of major earthquakes Types of Seismic Wave The shifting rock in an earthquake causes vibrations called seismic waves that travel within Earth or along its surface. Scientists use an instrument called a seismograph to record data about seismic waves. This information yields information that can help scientists learn not only about earthquake behavior but also about the structure of Earth itself. There are two broad classes of seismic waves: body waves and surface waves. Body waves travel within the body of Earth. They include P, or primary, waves and S, or secondary, waves. P waves cause the ground to compress and expand, that is, to move back and forth, in the direction of travel. They are called primary waves because they are the first type of wave to arrive at seismic recording stations. P waves can travel through solids, liquids, and even gases. S waves shake the ground in a shearing, or crosswise, motion that is perpendicular to the direction of travel. These are the shake waves that move the ground up and down or from side to side. S waves are called secondary waves because they always arrive after P waves at seismic recording stations. Unlike P waves, S waves can travel only through solid materials. After both P and S waves have moved through the body of Earth, they are followed by surface waves, which travel along Earth’s surface. Surface waves travel only through solid media. They are slower-moving than body waves but are much larger and therefore more destructive. Seismic waves are fundamentally of two types, compressional, longitudinal waves or shear, transverse waves. Through the body of the Earth these are called P-waves (for primary because they are fastest) and S-waves (for secondary since they are slower). Body waves - travel through the Earth’s interior Surface waves - travel along the Earth’s surface; similar to ocean waves Types of Body Waves A body wave is a seismic wave that moves through the interior of the earth, as opposed to surface waves that travel near the earth's surface. P and S waves are body waves. Each type of wave shakes the ground in different ways. Body waves Body waves are of two types: compressional or primary (P) waves and shear or secondary (S) waves. P- and S- waves are called "body waves" because they can travel through the interior of a body such as the Earth's inner layers, from the focus of an earthquake to distant points on the surface. The Earth's molten core can only be traveled through by compressional waves. P-waves travel fastest, at speeds between 4-8 km/sec (14,000-28,000 km/h) in the Earth's crust. S-waves travel more slowly, usually at 2.5-4 km/sec (9,000-14,000 km/h). Sound waves are usually called P-waves and are heard but not often felt. Except in the most powerful earthquakes they generally do not cause much damage. P-waves shake the ground in the direction they are propagating, while S-waves shake perpendicularly or transverse to the direction of propagation (i.e. they displace material at right angles to their path). P and S waves The P-wave is the first to arrive at a location, as it is the fastest. The P wave, or compressional wave, ultimately compresses and expands material in the same direction it is travelling. The next to arrive is the S wave which causes particles to oscillate. S waves can travel through solid material but not through liquid or gas. P waves or Compression Waves A P-wave, or primary wave, is one of the two main types of elastic body waves, called seismic waves in seismology. P-waves travel faster than other seismic waves and hence are the first signal from an earthquake to arrive at any affected location or at a seismograph. P-waves may be transmitted through gases, liquids, or solids. P-waves oscillate through compression and expansion in the same direction of movement; fastest of the serismic waves S waves or Shear waves In seismology, S-waves, secondary waves, or shear waves are a type of elastic wave and are one of the two main types of elastic body waves, so named because they move through the body of an object, unlike surface waves. S-waves oscillate in a direction that is perpendicular to direction of movement; second fastest seismic wave. It can only travel through solids. Surface waves Surface waves, in contrast to body waves can only move along the surface. They arrive after the main P and S waves and are confined to the outer layers of the Earth. They cause the most surface destruction. Earthquake surface waves are divided into two different categories: Love and Rayleigh. Love waves have a particle motion, which, like the S-wave, is transverse to the direction of propagation but with no vertical motion. Their side-to-side motion (like a snake wriggling) causes the ground to twist from side to side, that's why Love waves cause the most damage to structures. Rayleigh waves create a rolling, up and down motion with an elliptical and retrograde particle motion confined to the vertical plane in the direction of propagation. Surface waves are generally not generated by deep earthquakes. Particle motion for Rayleigh and Love waves are different: Rayleigh waves have retrograde particle motion confined to the vertical plane of motion, whereas Love waves have purely transverse motion in the horizontal plane. Earthquakes radiate seismic energy as both body and surface waves but deep earthquakes generally do not generate surface waves. These are the slowest seismic waves; may cause the greatest damage in an earthquake. Types of Surface Waves The two types of surface waves are named Love waves and Rayleigh waves, after the scientists who identified them. Love Waves Love waves have a horizontal motion that moves the surface from side to side perpendicular to the direction the wave is traveling. Of the two surface waves, Love waves move faster. The first kind of surface wave is called a Love wave, named after A.E.H. Love, a British mathematician who worked out the mathematical model for this kind of wave in 1911. It's the fastest surface wave and moves the ground from side-to-side. Confined to the surface of the crust, Love waves produce entirely horizontal motion.Click here to see a Love wave in action. Rayleigh Waves Rayleigh waves cause the ground to shake in an elliptical pattern. This motion is similar to that observed in ocean waves. Of all the seismic waves, Rayleigh waves spread out the most, giving them a long duration on seismograph recordings. The other kind of surface wave is the Rayleigh wave, named for John William Strutt, Lord Rayleigh, who mathematically predicted the existence of this kind of wave in 1885. A Rayleigh wave rolls along the ground just like a wave rolls across a lake or an ocean. Because it rolls, it moves the ground up and down, and side-to-side in the same direction that the wave is moving. Most of the shaking felt from an earthquake is due to the Rayleigh wave, which can be much larger than the other waves. Click here to see a Rayleigh wave in action. What drives the movement of tectonic plates? Mantle convection currents, ridge push and slab pull are three of the forces that have been proposed as the main drivers of plate movement There are a number of competing theories that attempt to explain what drives the movement of tectonic plates. Three of the forces that have been proposed as the main drivers of tectonic plate movement are: What is Convection Current -mantle convection currents— warm mantle currents drive and carry plates of lithosphere along a like a conveyor belt; A convection current is a process which involves the movement of energy from one place to another. Convection currents tend to move a fluid or gas particles from one place to another. These are created as a result of the differences occurring within the densities and temperature of a specific gas or a fluid Convection currents are the movement of fluid as a result of differential heating or convection. In the case of the Earth, convection currents refer to the motion of molten rock in the mantle as radioactive decay heats up magma, causing it to rise and driving the global-scale flow of magma What effect does convection have on Earth's interior? Convection in the mantle is the same as convection in a pot of water on a stove. Convection currents within Earth's mantle form as material near the core heats up. As the core heats the bottom layer of mantle material, particles move more rapidly, decreasing its density and causing it to rise. How do we use convection in everyday life? Everyday Examples of Convection Boiling water - The heat passes from the burner into the pot, heating the water at the bottom.... Radiator - Puts warm air out at the top and draws in cooler air at the bottom. Steaming cup of hot tea - The steam is showing heat being transfered into the air. What do convection currents cause? Convection currents are the result of differential heating. Lighter (less dense), warm material rises while heavier (more dense) cool material sinks. It is this movement that creates circulation patterns known as convection currents in the atmosphere, in water, and in the mantle of Earth. How does convection affect us? Convection currents are part of what drives global circulation of the Earth's atmosphere.... Convection currents in the air and sea lead to weather. Magma in the Earth's mantle moves in convection currents. The hot core heats the material above it, causing it to rise toward the crust, where it cools Why do convection currents cause plates to move? Plates at our planet's surface move because of the intense heat in the Earth's core that causes molten rock in the mantle layer to move. It moves in a pattern called a convection cell that forms when warm material rises, cools, and eventually sink down. As the cooled material sinks down, it is warmed and rises again What happens when tectonic plates move? When the plates move they collide or spread apart allowing the very hot molten material called lava to escape from the mantle. When collisions occur they produce mountains, deep underwater valleys called trenches, and volcanoes. What will happen if the Earth has no tectonic plates? Without tectonic forces, our lives will be greatly changed. Let's look at the social implications first. Without plate tectonics, there will be far less human deaths from natural disasters such as earthquakes, volcanic eruptions and even tsunamis. There would be much less destruction to the Earth. What happens if plate tectonics stopped? If all volcanism stops, so does sea floor spreading—and thus plate tectonics as well. And if plate tectonics stops, Earth eventually (through erosion) loses most or all of the continents where most terrestrial life exists. In addition, CO2 is removed from the atmosphere via weathering, causing our planet to freeze Will plate tectonics ever stop? The computer model showed that in Earth's youth, its interior was too hot and runny to push around the giant chunks of crust. After the planet's interior cooled for some 400 million years, tectonic plates began shifting and sinking. This process was stop-and-go for about 2 billion years What would happen if the convection currents stopped? If all convection currents on Earth stopped that would be a natural disaster. The amount of heat which the sun radiates at us sets the temperature of the Earth's surface.... So if convection completely stopped the high and low temperatures would force people and animals to move away from the poles and equator -ridge push (buoyant upwelling mantle at mid-ocean ridges) — newly-formed plates at oceanic ridges are warm, and so have a higher elevation at the oceanic ridge than the colder, more dense plate material further away; gravity causes the higher plate at the ridge to push away the lithosphere that lies further from the ridge; -slab pull — older, colder plates sink at subduction zones, because as they cool, they become more dense than the underlying mantle. The cooler sinking plate pulls the rest of the warmer plate along behind it. Recent research has shown that the major driving force for most plate movement is slab pull, because the plates with more of their edges being subducted are the faster-moving ones. However ridge push is also presented in recent research to be a force that drives the movement of plates. Mechanism behind Plate Tectonics The main features of plate tectonics are: The Earth's surface is covered by a series of crustal plates. The ocean floors are continually moving, spreading from the center, sinking at the edges, and being regenerated. Convection currents beneath the plates move the crustal plates in different directions. The source of heat driving the convection currents is radioactivity deep in the Earths mantle. Advances in sonic depth recording during World War II and the subsequent development of the nuclear resonance type magnometer (proton-precession magnometer) led to detailed mapping of the ocean floor and with it came many observation that led scientists like Howard Hess and R. Deitz to revive Holmes' convection theory. Hess and Deitz modified the theory considerably and called the new theory "Sea-floor Spreading". Among the seafloor features that supported the sea-floor spreading hypothesis were: mid-oceanic ridges, deep sea trenches, island arcs, geomagnetic patterns, and fault patterns. Mid-Oceanic Ridges The mid-oceanic ridges rise 3000 meters from the ocean floor and are more than 2000 kilometers wide surpassing the Himalayas in size. The mapping of the seafloor also revealed that these huge underwater mountain ranges have a deep trench which bisects the length of the ridges and in places is more than 2000 meters deep. Research into the heat flow from the ocean floor during the early 1960s revealed that the greatest heat flow was centered at the crests of these mid-oceanic ridges. Seismic studies show that the mid-oceanic ridges experience an elevated number of earthquakes. All these observations indicate intense geological activity at the mid-oceanic ridges. Geomagnetic Anomalies Occasionally, at random intervals, the Earth's magnetic field reverses. New rock formed from magma records the orientation of Earth's magnetic field at the time the magma cools. Study of the sea floor with magnometers revealed "stripes" of alternating magnetization parallel to the mid-oceanic ridges. This is evidence for continuous formation of new rock at the ridges. As more rock forms, older rock is pushed farther away from the ridge, producing symmetrical stripes to either side of the ridge. In the diagram to the right, the dark stripes represent ocean floor generated during "reversed" polar orientation and the lighter stripes represent the polar orientation we have today. Notice that the patterns on either side of the line representing the mid-oceanic ridge are mirror images of one another. The shaded stripes also represent older and older rock as they move away from the mid-oceanic ridge. Geologists have determined that rocks found in different parts of the planet with similar ages have the same magnetic characteristics. Deep Sea Trenches The deepest waters are found in oceanic trenches, which plunge as deep as 35,000 feet below the ocean surface. These trenches are usually long and narrow, and run parallel to and near the oceans margins. They are often associated with and parallel to large continental mountain ranges. There is also an observed parallel association of trenches and island arcs. Like the mid-oceanic ridges, the trenches are seismically active, but unlike the ridges they have low levels of heat flow. Scientists also began to realize that the youngest regions of the ocean floor were along the mid-oceanic ridges, and that the age of the ocean floor increased as the distance from the ridges increased. In addition, it has been determined that the oldest seafloor often ends in the deep-sea trenches. Island Arcs Chains of islands are found throughout the oceans and especially in the western Pacific margins; the Aleutians, Kuriles, Japan, Ryukus, Philippines, Marianas, Indonesia, Solomons, New Hebrides, and the Tongas, are some examples.. These "Island arcs" are usually situated along deep sea trenches and are situated on the continental side of the trench. These observations, along with many other studies of our planet, support the theory that underneath the Earth's crust (the lithosphere: a solid array of plates) is a malleable layer of heated rock known as the asthenosphere which is heated by radioactive decay of elements such as Uranium, Thorium, and Potassium. Because the radioactive source of heat is deep within the mantle, the fluid asthenosphere circulates as convection currents underneath the solid lithosphere. This heated layer is the source of lava we see in volcanos, the source of heat that drives hot springs and geysers, and the source of raw material which pushes up the mid-oceanic ridges and forms new ocean floor. Magma continuously wells upwards at the mid-oceanic ridges (arrows) producing currents of magma flowing in opposite directions and thus generating the forces that pull the sea floor apart at the mid-oceanic ridges. As the ocean floor is spread apart cracks appear in the middle of the ridges allowing molten magma to surface through the cracks to form the newest ocean floor. As the ocean floor moves away from the mid-oceanic ridge it will eventually come into contact with a continental plate and will be subducted underneath the continent. Finally, the lithosphere will be driven back into the asthenosphere where it returns to a heated state. Processes that occur along Plate Boundaries There are three main types of plate boundaries: Convergent boundaries: where two plates are colliding. Subduction zones occur when one or both of the tectonic plates are composed of oceanic crust.... Divergent boundaries – where two plates are moving apart.... Transform boundaries – where plates slide passed each other. Type of Plate Boundaries where Earthquakes and Volcanoes Occur There are three main places where volcanoes originate: Hot spots, Divergent plate boundaries (such as rifts and mid-ocean ridges), and Convergent plate boundaries (subduction zones) The origin of the magma for hot spots is not well known. We do know that the magma comes from partial melting within the upper mantle, probably from depths not too much greater than 100 km. The actual source of the heat that causes the partial melting (the actual hotspot itself) is almost certainly much deeper than that, but we really don't know how deep or even exactly what a hotspot is! At a divergent margin, two tectonic plates are moving apart, and magma that is generated in the upper mantle flows upward to fill in the space. This magma is probably generated at depths that are shallower than those for hotspot magmas. People argue about whether the magma forcing its way to the surface causes the plates to move apart or whether the plates move apart and the magma just reacts to that and fills in the space. Perhaps it is a combination of these two. The most extensive example of this type of volcanism is the system of mid-ocean ridges. Continental examples include the East African Rift, the West Antarctic Rift, and the Basin and Range Province in the southwestern US. The final major place where volcanism originates is at convergent margins (subduction zones)--where an oceanic plate dives under either another oceanic plate or perhaps a continental plate. As the plate gets pushed further and further it starts to give off its volatiles (mostly water), and these migrate upwards into the mantle just under the overriding plate. The addition of these volatiles to this overriding mantle probably lowers the melting point of that mantle so that magma is generated. Part of the magma may also be generated by the downgoing plate actually starting to melt as it gets into the hotter and hotter interior. Distribution of Earthquakes and Volcanoes Volcanoes and earthquakes are both found on plate boundaries. However, there is a difference between the two since volcanoes are never found on conservative and divergent boundaries because there is no change in crust to allow more magma (molten rock) to be made. How Are Earthquakes and Volcanoes Distributed? Volcanoes Distributed all over the world in different countries and continents but are not found it every country. Found mostly on the coastline Especially on tectonic plate boundaries Volcano prone areas: 'The Ring of Fire' Around the Pacific plate. Across the NOrth and South Atlantic ocean There are still anomalies - Hot spots Earthquakes Millions of tiny earthquakes happen everyday, but we only manage to notice the bigger, major ones. Found on mainland and coastlines Especially tectonic plate boundaries Earthquake prone areas: Around Pacific Ocean Along the Indo-Australian pate boundary Eastern side of Eurasian plate Western side of North American plate Volcanoes and Earthquakes Occur Volcanoes are most common in these geologically active boundaries. The two types of plate boundaries that are most likely to produce volcanic activity are divergent plate boundaries and convergent plate boundaries. At a divergent boundary, tectonic plates move apart from one another. Most earthquakes and volcanoes occur because of the movement of the plates, especially as plates interact at their edges or boundaries. At diverging plate boundaries, earthquakes occur as the plates pull away from each other. What is a tsunami and how is it created? A tsunami is a series of extremely long waves caused by a large and sudden displacement of the ocean, usually the result of an earthquake below or near the ocean floor. This force creates waves that radiate outward in all directions away from their source, sometimes crossing entire ocean basins. How tsunami are formed? A tsunami is a wave that spreads in the sea and is caused by an underwater earthquake, a landslide, a volcanic eruption or the fall of a meteorite. As the first cause is the most frequent one, we will focus on unravelling underwater earthquakes. The vast majority of earthquakes occur in faults. Rapid movement of the ocean floor displaces a column of water. Then, a series of waves travels outward at heights believed to be less than three feet. As a wave approaches land, its energy compresses into a smaller space, forcing it to gain height. Can you survive a tsunami underwater? If a vessel is hit by a tsunami near shore in shallow water, it will be shattered to pieces. Tsunamis can also be brutal to all sorts of life forms underwater. A diver, for instance, will hardly survive a tsunami because he will be caught by violent spinning currents. What is a Volcano? A volcano is an opening, or rupture, in the earth's crust or surface through which hot lava, volcanic ash, and gases to escape from the magma chamber below the surface. They are mountains that open downwards towards a pool of molten rock below the Earth’s surface. Eruptions happen when pressure builds up, lava shoots out the top of the volcano (the crater). It creates an ash cloud, it can cause mudslides, fire, tsunami, earthquakes and flash floods. On Earth, volcanoes are generally found where tectonic plates are diverging or converging. A mid-oceanic ridge, for example the Mid-Atlantic Ridge, has examples of volcanoes caused by divergent boundaries. The Pacific Ring of Fire has examples of volcanoes caused by convergent boundaries. What causes volcanoes? Volcanoes form when tectonic plates collide and one plate is pushed beneath another. Tectonic plates also move away from one another to produce volcanoes. Hot magma rises from the mantle at mid-ocean ridges pushing the plates apart. Volcanism It is any activity that includes the movement of magma towards the surface of the Earth. Magma rises because it is less dense than solid crustal rock. Lava is magma that erupts onto the surface. Vents are the opening in the surface where lava flows onto the surface. A volcano is the structure formed by the vent and the material that builds up on the surface. Origins of Volcanism There are four types of volcanism: - related with mid-ocean ridges - related with subduction zones - related with hotspots - related with flood volcanism What are the Types of Volcanoes? Fissure Volcano Fissure volcanoes are most often associated with oceanic ridges on diverging plate boundaries, they do also occur on land as well. Fissure volcanoes have no central crater and erupt large quantities of very fluid basaltic lava. This lava spreads out over large areas creating plateaus after successive eruptions. The best example of fissure volcanoes are in Iceland, which sits a top the Mid-Atlantic Ridge. Shield Volcano Shield volcanoes are built up over time after many eruptions pouring lava from a single vent. Slopes the usually around 15o, if the eruptions are regular the shield shape can expand many kilometres in circumference several kilometres high. Mauna Loa, Hawaii is an example of a shield volcano, it is 10km from its base on the sea floor to its peak 4km above sea level. This type of volcano is made of basaltic lava. It is some what like a composite volcano. Dome Volcano Dome volcanoes are created when felsic lavas are erupted as it is highly viscous and can hardly flow. There is very little spreading of the lava and they build up over time, due to the little movement the vent of the volcano often plugs. This means eruptions are often explosive as gasses are trapped, and blast the dome in fragments. The Dome volcano has high silica content and dynamic structure through out the volcano. Ash-cinder Volcano (Cinder-cone) Cinder cone volcanoes are built up over time from layers of ejecta (solid fragments) released from the volcano during an eruption. The ejecta is deposited in layers, the volcano builds up and angle is dependant on the maximum angle of stability. The lava is often liquid and explosive. It is a volcano that looks like a bowl crater. It is made out of basaltic material and takes a longer cycle to erupt. Composite Volcano Composite volcanoes are found along subduction zones, created by alternating layers of lava and ejecta (ash and rock fragments), lay down after each eruption. These composite volcanoes are are high, snow capped peaks often exceeding 2,500metres in height. The eruptions of composite volcanoes are explosive in nature, during the time between eruptions they are generally very quiet, dormant and often seen extinct. The lava from these volcanoes is very viscous, clogging the volcanoes vent, it also contains high levels of gasses which all add up to the explosiveness of the volcano. It is made out of layers of lava and looks like a tall, cone-shaped mountain. It also erupts different ways at different times Caldera Volcanoes Caldera volcanoes have a diameter of over 1 mile and are shaped more like and inverse crater. This vast crater is created by eruptions that are so explosive and power that the magma chamber is partially emptied and the volcano summit collapses into itself. This type of volcano are the largest volcanoes on Earth and have the potential to cause catastrophic damage if an eruption occurs. There have been no recent eruptions of any caldera volcanoes and the full affects of such an eruption occurring are unknown, the Yellowstone Caldera system in the USA is the most well documented caldera volcano at present. It is a volcano shaped more like a mountain than a bowl. Volcano Activities Extinct: is where the volcano will not explode with magma any more or the last explosion was before any written record; has not erupted for many thousands or millions of year (e.g. Edinburgh) Dormant (sleeping): is not extinct but probably wont erupt; these volcanoes have at least 1 written record of an eruption; has not erupted for many years (e.g. Mt. Pinatubo erupted in 1991 after 500 years of dormancy) Active: can erupt any moment or at any time; it has an 80% chance of eruption; liable to erupt (e.g. Mt. Etna & Mt. Merapi in Indonesia) However, it is often very difficult to tell whether a volcano will erupt again. El Chichon, Mexico erupted in 1982 after being dormant for approximately 1200 years. How a Volcano is formed Volcanoes form when tectonic plates collide and one plate is pushed beneath another. Tectonic plates also move away from one another to produce volcanoes. Hot magma rises from the mantle at mid-ocean ridges pushing the plates apart. Inside the Earth, heat and pressure cause rock to melt and turn to magma. Magma is forced up to the surface of the Earth because it is less dense (flows out through an opening called a vent). The lava cools quickly to form layers. Magma rises through cracks or weaknesses in the Earth’s crust. Pressure builds up inside the Earth. When this pressure is released, e.g. as a result of plate movement, magma explodes to the surface causing a volcanic eruption. The lava from the eruption cools to form a new crust. Over time, after several eruptions, the rock builds up and a volcano forms. Volcanic Eruption Volcanic eruptions happen when lava and gas are discharged from a volcanic vent. The most common consequences of this are population movements as large numbers of people are often forced to flee the moving lava flow. Volcanic eruptions often cause temporary food shortages and volcanic ash landslides called Lahar. The most dangerous type of volcanic eruption is referred to as a 'glowing avalanche'. This is when freshly erupted magma forms hot pyroclastic flow which have temperatures of up to 1,200 degrees. The pyroclastic flow is formed from rock fragments following a volcanic explosion , the flow surges down the flanks of the volcano at speeds of up to several hundred kilometres per hour, to distances often up to 10km and occasionally as far as 40 km from the original disaster site. The International Federation response adjusts to meet the needs of each specific circumstance. As population movement is often a consequence, the provision of safe areas, shelter, water, food and health supplies are primordial. In general response prioritizes temporary shelter materials; safe water and basic sanitation; food supplies; and the short term provision of basic health services and supplies. How does a Volcano Occur? Volcanoes erupt when molten rock called magma rises to the surface. Magma is formed when the earth's mantle melts.... If magma is thick, gas bubbles cannot easily escape and pressure builds up as the magma rises. When the pressure is too much an explosive eruption can happen, which can be dangerous and destructive. Pacific Ring of Fire in Volcanoes The Ring of Fire, also referred to as the Circum-Pacific Belt, is a path along the Pacific Ocean characterized by active volcanoes and frequent earthquakes.... Seventy-five percent of Earth's volcanoes—more than 450 volcanoes—are located along the Ring of Fire. What is The Ring of Fire - Volcanoes and The Ring of Fire. Why is the ring of fire dangerous? The Ring of Fire is home to 75% of the world's volcanoes and 90% of its earthquakes. This movement results in deep ocean trenches, volcanic eruptions, and earthquake epicenters along the boundaries where the plates meet, called fault lines. What would happen if the ring of fire erupted? All the plants would die, including all the crops that feed us and the animals. Even if the crops could somehow survive without the sun, they'd be wiped out by acidic rains. Because volcanic ash is actually tiny rock particles, it would be very heavy. How did the Ring of Fire form? The Ring of Fire was formed as oceanic plates slid under continental plates. Volcanoes along the Ring of Fire are formed when one plate is shoved under another into the mantle -- a solid body of rock between the Earth's crust and the molten iron core -- through a process called subduction. What is a Supervolcano? A supervolcano is a volcano on a massive scale. It is different from a volcano because: it erupts at least 1,000 km 3 of material (a large volcano erupts around 1 km 3) it forms a depression, called a caldera (a volcano forms a cone shape). By some reckonings the southern part of the Philippines island of Luzon has more active volcanoes per square kilometer than any other place.... A supervolcano erupted at Taal within the last 2 million years. The Phivolcs defines "active" as volcanoes that have erupted in the past 500 years. What is the strongest volcanic eruption in the Philippines? Pinatubo Eruption The Pinatubo eruption is considered to be the most powerful volcanic eruption of the 20th century. Thankfully, it was also the eruption that the Philippines was most prepared for, thanks to the joint efforts of the PHIVOLCS and the United States Geological Survey. Introduction to Earthquake Earthquake, any sudden shaking of the ground caused by the passage of seismic waves through Earth’s rocks. Seismic waves are produced when some form of energy stored in Earth’s crust is suddenly released, usually when masses of rock straining against one another suddenly fracture and “slip.” Earthquakes occur most often along geologic faults, narrow zones where rock masses move in relation to one another. The major fault lines of the world are located at the fringes of the huge tectonic plates that make up Earth’s crust. How are earthquakes caused? An earthquake is caused by a sudden slip on a fault.... When the stress on the edge overcomes the friction, there is an earthquake that releases energy in waves that travel through the earth's crust and cause the shaking that we feel. Causes of Earthquakes in General Induced Earthquakes Induced quakes are caused by human activity, like tunnel construction, filling reservoirs and implementing geothermal or fracking projects. Volcanic Earthquakes Volcanic quakes are associated with active volcanism. Collapse Earthquakes What makes earthquakes so dangerous? Earthquakes can be very dangerous, if you are in the wrong place. They can make buildings fall down and set off landslides, as well as having many other deadly effects. An earthquake that occurs at the bottom of the sea can push water upwards and create massive waves called tsunamis. Where do most earthquakes occur? Most earthquakes occur along the edge of the oceanic and continental plates. The earth's crust (the outer layer of the planet) is made up of several pieces, called plates. The plates under the oceans are called oceanic plates and the rest are continental plates. Which countries have the most earthquakes? Japan has the most recorded earthquakes in the world as it sits on a highly active seismic area, but research by the US Geological Survey suggests the answer is not quite as straightforward as it may seem. Which country has no earthquake? Antarctica has the least earthquakes of any continent, but small earthquakes can occur anywhere in the World. What country has the most earthquakes each year? Indonesia Which country actually has the most earthquakes? Indonesia is in a very active seismic zone, also, but by virtue of its larger size than Japan, it has more total earthquakes. Where is the safest place to be during an earthquake? The best move is getting under a strong table or desk. If no sturdy object is available, get next to an interior wall with no windows. Finally, HOLD ON to your shelter if you have one, as the temblor will likely involve great shaking. If you have no shelter, hold on to your neck and head with both arms and hands. Pacific Ring of Fire in Earthquakes The Ring of Fire, also referred to as the Circum-Pacific Belt, is a path along the Pacific Ocean characterized by active volcanoes and frequent earthquakes. The majority of Earth's volcanoes and earthquakes take place along the Ring of Fire. What is a Tsunami? What does the name “tsunami” mean and where did the term come from? Tsunami is a Japanese word 津波 that comes from two Chinese characters (kanji), 津 “tsu” which means harbor and 波 “name”, meaning wave. Like many compound words, it no longer strictly means a harbor wave, but now internationally is used to describe the series of surges in oceans or lakes following the displacement of the sea or lake floor, which moves the entire column of water above it. Impacts are often greatest in harbors where people and structures are concentrated at sea level. Earthquakes as Driving Mechanism Behind Tsunami In subduction zones we see convergent plate boundaries where two plates are colliding with each other and one of the plates is subducting back into the Earth. This type of plate boundary is particularly effective for causing tsunamis. Tsunamis are caused by violent seafloor movement associated with earthquakes, landslides, lava entering the sea, seamount collapse, or meteorite impact. The most common cause is earthquakes. See the percentages on the right for the geological events that cause tsunamis. Note that 72% of tsunamis are generated by earthquakes. A disturbance that displaces a large water mass from its equilibrium position can cause a tsunami. Trenches Ocean trenches are steep depressions in the deepest parts of the ocean [where old ocean crust from one tectonic plate is pushed beneath another plate, raising mountains, causing earthquakes, and forming volcanoes on the seafloor and on land. With depths exceeding 6,000 meters (nearly 20,000 feet), trenches make up the world’s "hadal zone," named for Hades, the Greek god of the underworld, and account for the deepest 45 percent of Trenches are formed by subduction, a geophysical process in which two or more of Earth's tectonic plates converge and the older, denser plate is pushed beneath the lighter plate and deep into the mantle, causing the seafloor and outermost crust (the lithosphere) to bend and form a steep, V-shaped depression. This process makes trenches dynamic geological features—they account for a significant part of Earth’s seismic activity—and are frequently the site of large earthquakes, including some of the largest earthquakes on record. Subduction also generates an upwelling of molten crust that forms mountain ridges and volcanic islands parallel to the trench.the global ocean. Ocean Ridges Oceanic ridge, continuous submarine mountain chain extending approximately 80,000 km (50,000 miles) through all the world's oceans. Individually, ocean ridges are the largest features in ocean basins. Making of Sinkhole Epicenter of an Earthquake The epicenter is the point on the earth's surface vertically above the hypocenter (or focus), point in the crust where a seismic rupture begins. The point within Earth where rock under stress breaks is called the focus. The point directly above the focus on the surface is the epicenter. What is a Rift A rift valley is a lowland region that forms where Earth's tectonic plates move apart, or rift. Rift valleys are found both on land and at the bottom of the ocean, where they are created by the process of seafloor spreading. What is a Mountain belt A mountain system or mountain belt is a group of mountain ranges with similarity in form, structure, and alignment that have arisen from the same cause, usually an orogeny. Mountain ranges are formed by a variety of geological processes, but most of the significant ones on Earth are the result of plate tectonics. Disaster Preparedness The Philippines is one of the most high-risk countries in the world for experiencing natural disasters. The list of possible natural disasters includes earthquakes, floods, mudslides, typhoons, and volcanic eruptions. The Philippines is considered to be one of the most storm-exposed countries on Earth. On average, 18 to 20 tropical storms enter Philippine waters each year, with 8 or 9 of those storms making landfall. Situated on the Ring of Fire, the Philippines has a number of active volcanoes which periodically threaten their immediate vicinities. The Mayon, Taal and Bulusan volcanoes have a permanent danger zone (PDZ) established around their summits by the Philippine Institute of Volcanology and Seismology (PHIVOLCS). Mayon volcano in Albay Province has a PDZ of six kilometres, Bulusan volcano in Sorsogon has a four kilometre PDZ and the entire volcanic island of Taal is a PDZ. You should take this information into account when traveling to these areas. In the event of major volcanic activity, you should follow the advice of local authorities and monitor warnings issued by the Philippine Institute of Volcanology and Seismology (PHIVOLCS). Preparing Your Family and Home for Natural Disasters The following list contains general suggestions on how to best be prepared in the event that you and your family lose power for extended periods or experience restrictions in travel or mobility: 1. fill vehicle and generator fuel tanks; 2..secure loose outdoor items around your home; 3. check and charge all mobile phones and emergency radios; 4. check and assemble flashlights, first aid kids, and tools; 5. procure batteries, candles, matches, potable water, canned or dry food, ped food, medication, and other supplies needed to support you and your household for extended periods.