Earth Science Quarter 2 PDF

EARTH SCIENCE Q2 Hydrolysis - Rock-forming minerals like amphibole, pyroxene, and feldspar react with water and form different EXOGENIC PROCESS...

EARTH SCIENCE Q2 Hydrolysis - Rock-forming minerals like amphibole, pyroxene, and feldspar react with water and form different EXOGENIC PROCESS kinds of clay minerals. The solid portion is made from rocks and minerals that Oxidation - the response of oxygen with minerals. If the iron could experience changes either physically or chemically. oxidizes, the mineral in rocks decomposes. Rusting is an The weathered materials are transported by different example of this chemical reaction. agents from one place to another and will settle down in a particular area. It includes weathering, erosion, and deposition. EROSION - the separation and removal of weathered rocks WEATHERING due to different agents like water, wind, and glacier that causes transportation of the material to where they are the process of disintegration (physical) and decomposition deposited. (chemical) of rocks. a process of breaking down rocks into small particles such Plants, animals, and humans play an important role in the as sand, clay, gravel and other fragments. erosional process. two types of weathering: mechanical weathering and chemical weathering. Mass wasting - movement of sediments downslope under the influence of gravity. MECHANICAL WEATHERING Example: fall, slide, avalanche, and flow. (physical weathering) is the breakdown of rocks into pieces without any change in its composition. DEPOSITION - the weathered materials carried out by erosion settle down in a particular location. - the size and shape of rocks changes and this occurs because of the following factors shown below: Pressure - Due to tectonic forces, granite may rise to form THE EARTH'S INTERNAL HEAT mountain range. Sources of heat in our planet can be identified as Primordial Temperature - Rocks expand and are fractured when expose and Radiogenic heat. to high temperature. PRIMORDIAL HEAT Frost Wedging - rocks have fracture in its surface and when During the early formation of the Earth, the internal heat water accumulates in the crack and at that point freezes, the energy that gradually gathered by means of dispersion in the ice expands and breaks the rock apart. planet during its few million years of evolution is called Abrasion – breakdown of rocks is caused by impact and Primordial heat. friction. Occurs during collision of rocks, sand, and silt due The major contribution of this internal heat is the to current or waves along a stream or seashore causing accretional energy - the energy deposited during the early sharp edges and corners to wear off and become rounded. formation of a planet. Organic activity – roots growing causing penetration into the The core is a storage of primordial heat that originates from crack, expand, and in the long run, break the rock. times of accretion when kinetic energy of colliding particles Human activity – digging, quarrying, denuding forests ad was transformed into thermal energy. cultivating and contribute to physical weathering. This heat is constantly lost to the outer silicate layers of the Burrowing animals – animals like rats, rabbits and squirrel mantle and crust of the earth through convection and excavate into the ground to create a space for habitation. conduction CHEMICAL WEATHERING RADIOGENIC HEAT Rocks break down by chemical reactions. ❖The thermal energy released as a result of spontaneous New or secondary minerals develop and sometimes nuclear disintegration is called Radiogenic Heat. replace the original properties of the minerals in the ❖It involves the disintegration of natural radioactive original rock or soil. elements inside the earth like Uranium, Thorium and In chemical weathering, there are changes in the Potassium. composition of rocks due to the chemical reactions present below: ❖Uranium is a special kind of element because when it Chemical Reactions decays, heat (radiogenic) is produced. Dissolution - occurs in specific minerals which are dissolved ❖Estimated at 47 terawatts (TW), the of heat from Earth's in water. Examples of these minerals are Halite (NaCl) and interior to the surface and it comes from two main sources in Calcite (CaCO3). The formation of stalactites and flow equal amounts: the radiogenic heat produced by the stalagmites in caves are brought about by this chemical radioactive decay of isotopes in the mantle and crust, and reaction. the primordial heat left over from the formation of the Earth.  Sources of Heat and Heat Transfer 6 FACTORS THAT AFFECTS THE PROCESS OF MAGMA FORMATION Both sources of heat whether primordial or radiogenic undergo heat transfer and it plays an important role to the HEAT AND PRESSURE continuous changes and development of our planet. Deep within the Earth, intense heat from the core and high- Three processes can transfer heat: pressure cause rocks to melt and form magma. Conduction DECOMPRESSION MELTING ✓ Conduction governs the thermal conditions in almost Magmatism plays a key role in mountain formation, as new entire solid portions of the Earth and plays a very important ascending magmas produce additional mass and volume to role in the lithosphere. the Earth’s surface and subsurface. Magmas form by partial melting of silicate rocks either in Earth's mantle, the ✓ Its processes happen in the earth's surface. continental or the oceanic crust. ✓ Conduction is one of the three main ways that heat energy ADDITION OF VOLATILES moves from place to place. Technically, it can be defined as the process by which heat energy is transmitted through Water and other volatiles are introduced, lowering the collisions between neighboring atoms or molecules. melting point of rocks, which helps in magma formation. Convection Volatiles are the group of chemical elements and chemical compounds that can be readily vaporized. In ✓ Convection involves transfer of heat by the movement of contrast with volatiles, elements and compounds that mass, which is a more efficient means of heat transport in are not readily vaporized are known as refractory the Earth compared to pure conduction. substances. ✓ Convection dominates the thermal conditions in the zones TEMPRERATURE INCREASE where large quantities of fluids (molten rocks) exist, and thus governs the heat transport in the fluid outer core and the Rocks that are forced deeper into the Earth’s mantle mantle. experience rising temperatures, eventually melting into magma radiation SUBDUCTION ZONES ✓Radiation is the least important mode of heat transport in the Earth. The process of heat exchange between the Sun At convergent boundaries, oceanic plates sink into the and the Earth, through radiation, controls the temperatures mantle, carrying water and volatiles, which leads to magma at the Earth's surface. creation. MANTLE PLUMES GROUP 1 - MAGMA FORMATION Hotter regions in the mantle, known as plumes, rise towards the Earth’s surface, and the drop in pressure causes these Magma is the molten or partially molten rock beneath the plumes to melt and form magma. Earth's surface. Magmatism is a process under the Earth’s crust where formation and movement of magma occur. these happen in the lower part of the Earth’s crust and in the upper portion of the mantle known as the asthenosphere The distinction between magma and lava is all about location. When geologists refer to magma, they're talking about molten rock that's still trapped underground. If this molten rock makes it to the surface and keeps flowing like a liquid, it's called lava. Magmatism plays a key role in mountain formation, as new ascending magmas produce additional mass and volume to the Earth’s surface and subsurface. Magmas form by partial melting of silicate rocks either in Earth's mantle, the continental or the oceanic crust.  TYPES OF MAGMA When enough mass and buoyancy is attained, the overlying surrounding rock is pushed aside as the magma rises. Basaltic Magma: Depending on surrounding pressure and other factors, the Low silica, fluid, with a density of 2650- magma can be ejected to the Earth's surface or rise at 2800 kg, found at mid-ocean ridges and hot spots. shallower levels underneath usually black to dark brown in color. The magma starts to accumulate and slowly solidifies. Andesitic Magma: Upon being expelled, the lava continues to flow until it hardens into rock. This type of rock is known as igneous Intermediate silica, 2450–2500 kg dense rock and is classified into two major categories. more viscous, found at convergent boundaries. Andesite is a gray to black volcanic rock magma commonly erupts from stratovolcanoes erupt at temperatures between 900 and 1100 ° C. Rhyolitic Magma: High silica, with a density of 2180–2250 kg, very viscous, associated with explosive eruptions. does not flow very far from the place where it erupted. Rhyolitic lava is therefore more sluggish, moves more slowly and builds thicker lava flows than basalt. Important concepts derived from the Bowen’s reaction series: A mafic magma will crystallize into pyroxene (with or without olivine) and calcium-rich plagioclase (basalt or gabbro) if the early formed crystals are not removed from the remaining magma. Similarly, an intermediate magma will crystallize into diorite or andesite, if early formed minerals are not removed. If minerals are separated from magma, the remaining magma is more silicic than the original magma. When rocks are heated in high temperatures, minerals will melt in reverse order. If the temperature is raised further, biotite and sodium-rich plagioclase would contribute to the melt. Any minerals higher in the series would remain solid unless the temperature is raised GROUP 2 - WHAT HAPPENS AFTER MAGMA IS further. FORMED Magma is a molten and semi-molten rock mixture found DISCONTINUOUS BRANCH under the surface of the Earth. This mixture is usually made up of four parts: a hot liquid base, called the melt; minerals describes how ferromagnesian minerals in the magma crystallized by the melt; solid rocks incorporated into the are transformed as temperature changes. melt from the surrounding confines; and dissolved gases. The early formed crystals, olivine in this case, reacts with the remaining melt as the magma cools down, and After magma is formed, it rises as it is less dense than the recrystallizes into pyroxene. surrounding rock. It then accumulates in magma chambers until it makes its way to the surface where it is then expelled Further cooling will transform pyroxene into amphibole. as lava. If all iron and magnesium in the melt is used up before all the pyroxene recrystallizes to amphibole, then the ferromagnesian minerals in the solid rock would be DENSITY CONTRAST amphibole and pyroxene and would not contain olivine or biotite. Magma is less dense than the surrounding country rock. Olivines are an important rock-forming mineral group. Magma rises faster when the difference in density between Magnesium-rich olivines are abundant in low-silica mafic the magma and the surrounding rock is greater. and ultramafic igneous rocks and are believed to be the most abundant constituent of the Earth's upper mantle At deeper levels, magma passes through mineral grain boundaries and cracks in the surrounding rock. Pyroxene the most significant and abundant group of rock- forming ferromagnesian silicates. They are found in almost every variety of igneous rock and also occur in rocks of Strain widely different compositions formed under conditions of regional and contact metamorphism. - When rocks deform they are said to strain. - A strain is a change in size, shape, or volume of a material. MAGMATIC DIFFERENTATION STAGES OF DEFORMATION the process of creating one or more secondary magmas Elastic Deformation - strain is reversible. from single parent magma Ductile Deformation - strain is irreversible. CRYSTAL FRACTIONATION Fracture - irreversible strain wherein the material breaks. A chemical process by which the composition of a liquid, such as magma, changes due to crystallization. FACTORS AFFECTING DEFORMATION Common mechanism for crystal fractionation is crystal Temperature settling. At high temperature molecules and their bonds can stretch This means that denser minerals crystallize first and and move, thus materials will behave in more ductile settle down while the lighter minerals crystallize at the manner. At low Temperature, materials are brittle. latter stages. Bowen's reaction series shows that denser minerals such Confining Pressure as olivine and Ca-rich plagioclases form first, leaving the At high confining pressure materials are less likely to magma more silicic. fracture because the pressure of the surroundings tends to PARTIAL MELTING hinder the formation of fractures. At low confining stress, material will be brittle and tend to fractur sooner. As described in Bowen's reaction series, quartz and muscovite are basically the most stable minerals at the Strain Rate Earth's surface, making them the first ones to melt from the parent rock once exposed in higher temperature and/or At high strain rates material tends to fracture. At low strain pressure. rates more time is available for individual atoms to move and therefore ductile behavior is favored Partial melting of an ultramafic Rock in the mantle produces a basaltic Magma. Composition MAGMA MIXING Some minerals are very brittle. This is due to the chemical Occur when two different magma rises, with the more bond types that hold them together. Thus, the mineralogical buoyant mass overtakes the more slowly rising body. composition of the rock will be a factor in determining the deformational behavior of the rock. Convective flow then mixes the two magmas, generating a single, intermediate (between the two parent magmas) magma Strike - the compass direction of any horizontal line on the ASSIMILATION/CONTAMINATION OF MAGMA BY plane. CRUSTAL ROCKS Dip - the angle between a horizon plane and the inclined A reaction that occurs when the crust is mixed up with the plane, measured perpendicular to the direction of strike. rising magma. Joint - A joint is a fracture along which no movement has As magma rises to the surface, the surrounding rocks taken place, usually caused by tensional forces. which it meets may get dissolved (due to the heat) and get mixed with the magma. Fault - a fracture or break in the rock along which movement has taken place Tensional GROUP 3 – ROCK’S BEHAVIOR UNDER DIFFERENT TYPES OF STRESS Stress Tension stretches rock. Stress Compressional Stress - The forces acting on rock are called stress. Compression stresses act toward each other, pushing or squeezing rock together. - the force applied on a rock per unit area. When rocks experiencing compressive stress deform Shear stresses may act toward or away from each other, but plastically, the rocks crumple into folds. they do so along different lines of action, causing rock to twist or tear. Shearing can cause masses of rock to slip. Anticlines are folds where the originally horizontal strata has conditions, allowing rocks to flow or bend instead of been folded upward, and the two limbs of the fold dip away breaking. Ductile shearing can lead to the formation of folds from the hinge of the fold. and other structural features. Synclines are folds where the originally horizontal strata have been folded downward, and the two limbs of the fold dip inward toward the hinge of the fold. Characteristics Shear zones often exhibit features such as foliation, mylonitization (fine-grained, deformed rock), and changes in Reverse Faults mineralogy due to pressure and temperature conditions. forms when compressional forces cause the hanging wall (the block of rock above the fault) to move upward relative to the footwall (the block below the fault). 4.Faulting and Shearing typically steep and occur when the crust is shortened. Fault Types: common in mountain-building regions where tectonic Shearing is a primary mechanism for faulting, which can be plates collide, like the Himalayas. categorized into: Thrust Faults Normal Faults: Occur under extensional stress where the hanging wall moves down relative to the footwall a special type of reverse fault with a lower-angle slope (less than 30 degrees). Reverse (Thrust) Faults: Occur under compressional stress where the hanging wall moves up relative to the footwall. These faults result from strong compressional forces and can displace large sections of the Earth's crust over great Strike-Slip Faults: Result from horizontal shearing, where distances. rocks slide past each other with little vertical movement. commonly found in large-scale mountain- building events 5. Effects of Shearing (orogeny), such as at convergent plate boundaries, where Structural Changes: one plate is thrust over another. Shearing can lead to changes in rock structure, including Fold-and-Thrust Belts the formation of new minerals, alteration of existing ones, In some regions of strong compression, rocks can bend or and the development of lineations and foliation. fold instead of fracturing immediately. Over time, the Landslides: compression causes a combination of folding and thrusting, resulting in "fold-and-thrust" In certain conditions, shearing can cause landslides, where large masses of rock and soil move downhill rapidly due to gravity. Shearing in the context of rock mechanics refers to the STRESS TYPE EFFECT REASON process by which rocks deform or fail due to shear stress. Compression Shortening Forces pushing This deformation can occur along faults, during landslides, or thickening, folding, rocks together in response to tectonic forces. Here's an overview of how reverse fault shearing affects rocks: Tension Stretching, thinning, Forces pulling normal fault, fracture rocks apart Shear Twisting, horizontal Forces sliding 1. Shear Stress displacement, strike- past each other slip fault Shear stress is the force per unit area acting parallel to the surface of a material. It is a critical factor in determining how rocks will respond to applied forces. 2. Types of Shearing GROUP 4 - LAYERS OF THE EARTH Brittle Shearing SEISMIC WAVES are vibrations generated by an earthquake, explosion, or similar energetic source and propagated within Occurs when rocks break or fracture due to applied shear the Earth or along its surface stress. This typically happens in stronger rocks or under low- temperature and low-pressure conditions. The result can be Rheology is the study of the flow of matter primarily in the faulting, where rocks slide past each other along a fracture. liquid state under conditions at which they respond with plastic flow rather than deforming elastically in response to Ductile Shearing an applied force. Involves the gradual deformation of rocks without fracturing. This occurs under high temperature and pressure Mechanically been called the Moho discontinuity, a zone that separates the crust and mantle. LITHOSPERE - the outer solid part of the planet including Earth's crust. depth 70-100 km. ASTHENOSPHERE, a highly viscous, hotter, and ductile Earth's Mantle region of the upper mantle that is involved in plate tectonic movement and isostatic adjustments. The mantle is the layer beneath the Earth's crust and under the Moho. This layer reaches almost halfway to the centre of MESOSPHERIC Mantle (lower mantle) more rigid and the earth. It is the thickest layer, extending from the base of immobile than the asthenosphere. The mesosphere is the crust to a depth of approximately 2,900 kilometers subjected to very high pressures and temperatures. These extreme conditions create a transition zone in the upper Upper Mantle mesosphere where minerals continuously change into The upper mantle is relatively rigid and contains the various forms or pseudomorphs asthenosphere, a semi-fluid layer that allows the movement OUTER CORE extends from 2,880 km to 5,036 km from the of tectonic plates. mantle. composed of iron-rich metal alloy, and it is inferred The Upper 5 km is the upper mantle, composed chiefly of to be liquid in form. Seismologists inferred that the outer silicates of metallic compound that are different from the core is in liquid form because the elements that combine crust with iron have lower melting point than iron. Lower Mantle INNER CORE comprises the entire center of the earth's interior. This layer is inferred to be composed of heavy iron The solid lower mantle contributes to the overall convection and nickel, which are solid in form, very dense but highly and heat transfer within the Earth's interior. elastic. These materials release gravitational energy and heat of fusion that conduct and drive electricity on the layers The lower 1,930 km is the lower mantle, which is composed above it - a condition that explains the earth's magnetism. of magnesium and iron. Chemically Earth's Core Earth's Crust The core is the innermost and the central region of the earth's interior. It extends to about 3,200 km from the mantle. Its The crust is the outermost layer of the Earth. It is the thinnest temperature is about 3,038°C and has a pressure of three layer, ranging from about 5 to 70 kilometers in thickness. This million atm. Analysis of the behaviour of seismic waves layer shows great variations in thickness and composition. revealed that the core is divided into two distinct regions: the Divided into two types: continental crust and oceanic crust. outer core and the inner core. Continental Crust Outer Core The continental crust is 30 to 50 km thick. It is chiefly The outer core is a liquid layer composed mainly of molten composed of rocks rich with silicon aluminum (SiAl). iron and nickel. It has a thickness of about 2,300 kilometers. GRANITE is the basic type of rock that composes the Inner Core continental crust. The inner core is the solid, central part of the earth. It has a Oceanic Crust radius of about 1,220 kilometers and is composed of solid iron and nickel The oceanic crust is comparatively thinner, being about 7.5 km thick. It is chiefly composed of rocks rich with silicon, iron, and magnesium (Sima). Chemical layers classify based on what each layer is made of BASALT is the basic type of rock that composes this region of (composition). Mechanical layers classify based on how the crust. each layer behaves physically (rigid, fluid, or ductile). ANDRIJA MOHOROVICIC a Croatian seismologist, noticed a marked change in the way Magnetic field seismic or earthquake waves moved upon reaching a depth of 32 to 48 km As Earth rotates, the outer core spins over the inner core and generates Earth's magnetic field. He observed using a seismogram that the seismic waves moved much faster upon reaching such depth. Mohorovicic Due to convection by heat radiating from the core together concluded that when compared to the crust, this zone differs with the rotation of Earth in its axis, the liquid iron moves in a in density, causing the earthquake waves to travel faster. In rotational pattern which is believed to be the source of the recognition of his worthwhile discovery, this rigid zone has magnetic field of Earth. This circulating current is called the DYNAMO EFFECT. The A divergent boundary occurs when two tectonic plates magnetic field is detected using a compass. move apart. Earthquakes are common along these boundaries as magma rises from the Earth's mantle, An increase in cosmic rays can temporarily affect solidifying to form new oceanic crust. communication systems satellites, power grids, cable, hasten ozone layer depletion, and generate aurora phenomenon. Mantle Convection Gravitational heat convection in the mantle drives the The geomagnetic field protects us from the harmful rays movement, bending, and breaking of rocks in the Earth's emitted by the sun lithosphere. This heat comes from the radioactive decay of unstable isotopes and residual heat from Earth's formation billions of years ago. GROUP 5 – HOW SEAFLOOR SPREADS New Crust Formation SEAFLOOR SPREADING happens at pens at mid-ocean As plates diverge, molten rock from the Earth's mantle rises ridges where new oceanic crust forms as plates move apart. to the surface, cools, and solidifies to form a new oceanic crust. spreading rates Seafloor spreading rates vary globally, influencing plate boundary shapes. Fast-spreading ridges result in smoother seafloors, while slow-spreading ones create rugged terrain, balanced by subduction at convergent THE MID-OCEAN RIDGE SYSTEM boundaries. Underwater Mountain Range The mid-ocean ridge is an underwater mountain range Evidence for Seafloor Spreading formed by plate tectonics, featuring a central rift valley where new oceanic crust is created as tectonic plates diverge. In 1960, Harry Hess studied Wegener's theory. The Purpose of Hydrothermal Vents Hess proposed the radical idea that the ocean floors move like a conveyor belt, which in turn moves the continents. Hydrothermal vents function as natural plumbing systems, transporting heat and chemicals from the Earth's interior and regulating global ocean chemistry. They also support unique ecosystems with organisms that have adapted to high Continental Drift temperatures and toxic environments. The continental drift hypothesis, developed by Alfred Seafloor Spreading and Ocean Formation Wegener in the early 20th century, posits that continents move across Earth's surface and were once united as a single Ocean basins are formed by plate tectonic activity, supercontinent. weathering, and erosion. Seafloor spreading and subduction are key processes that allow molten rock to escape the Seafloor Mapping mantle and create new oceanic crust. In subduction, two Seafloor mapping is the initial step in ocean exploration. tectonic plates collide, causing the heavier plate to slide Scientists and resource managers use ships with multibeam beneath the lighter one. sonar to collect data and create high-resolution bathymetric maps of targeted areas. Magnetic Stripe Patterns on the Seafloor Plate Tectonic Earth's Magnetic Field Seafloor spreading is a cornerstone of plate tectonics, a theory that explains Earth's dynamic surface and the When the Earth's magnetic field reverses, new stripes with processes that shape it. the new polarity form on the ocean floor. These magnetic patterns provide strong evidence for sea-floor spreading and support the theory of plate tectonics. 1953, American oceanic cartographer Marie Tharp had created the first of several maps that revealed the presence of an underwater mountain range more than 16,000 km Magnetic Stripes (10,000 miles) long in the Atlantic-the Mid-Atlantic Ridge. New crust forms along the ridge as old crust splits and magma rises to fill the gap. This ongoing divergence eventually splits the new crust, pushing the halves in TECTONIC PLATE MOVEMENT AND DIVERGENT opposite directions. BOUNDARIES Symmetrical Patterns Magnetic polarity is normal at the ridge crest but reversed in process called subduction, where one plate goes under symmetrical patterns away from the ridge center. another. 4. New Oceans and Subduction: The separation of continents like Greenland from Europe created new oceanic crust, like the Norwegian Sea and the Arctic Ocean. In the Indian Ocean, spreading ridges formed new ocean floors as Australia and Antarctica continued to separate. 5. Mediterranean and Caribbean Seas: In the Mediterranean region, ocean floors formed due to complex interactions between small tectonic plates. The Mediterranean Sea almost dried up about 6 million years ago. The Caribbean Sea was formed as North America and South America shifted, with much of its older seafloor coming from the Pacific Ocean basin. GROUP 6 - THE STRUCTURE AND EVOLUTION OF OCEAN BASINS What is an ocean basin and how does it form? STRUCTURE OF OCEAN BASINS An ocean basin is a bowl-shaped depression in the earth, The planet's surface is made up of about 70% of ocean with complex topography along its deep seafloor. All ocean basins, which are the regions that are below sea level. basins are formed from plate tectonic activity, weathering, These areas hold the majority of the planet's water. and erosion. Seafloor spreading and subduction are the primary forms of plate tectonic activity that provide a Thus, an ocean basin can be thought of a large bowl that pathway for molten rock to leave the earth's mantle and holds ocean water. create a new oceanic crust. During seafloor spreading, the tectonic plates pull away from each other. Through subduction, two tectonic plates collide, forcing the heavier OCEANIC BASIN LANDFORMS plate to slide over the lighter plate. Land exists under an ocean What is an example of an ocean basin? Oceanic basins have different topographical features: The Atlantic Ocean is one of five ocean basins in the world. It formed when the tectonic plates beneath Europe, Africa, and Mid-ocean Ridges America separated from each other. Seafloor spreading is one form of tectonic activity that still occurs within this Occur along divergent plate boundaries, where new ocean basin, causing the Atlantic Ocean to expand slowly by 2 to 5 floor is created as the Earth's tectonic plates spread apart. centimeters a year. As the plates separate, molten rock rises to the seafloor, producing enormous volcanic eruptions of basalt. Ocean Trenches The history of ocean basins is closely tied to the movement of Earth's tectonic plates over millions of years, a process Are formed through subduction, which occurs when known as plate tectonics. tectonic plates collide and push one plate beneath the other. 1. Formation of Ocean Basins: About 200 million years ago, Abyssal Plain Earth’s continents were joined together in a massive The creation of the abyssal plain is the result of the supercontinent called Pangea. As tectonic plates moved, spreading of the seafloor (plate tectonics) and the melting of Pangea began to break apart, and the Atlantic Ocean started the lower oceanic crust. to form, while the Pacific Ocean shrank. Seamounts 2. Tectonic Plate Movements: North America and Eurasia began to drift away from Africa and South America, forming When two oceanic plates collide, the overridden oceanic new ocean floors, especially in the Atlantic Ocean. India plate is consumed within Earth's mantle. During that separated from Australia and Antarctica and drifted process, magma rises from the downgoing plate, leading to northward toward Asia, leading to the formation of the Indian an eruption that can form seamounts and islands. Ocean. This movement set the stage for the eventual collision between India and Asia, which created the Himalayas. Guyots 3. Ocean Floor Creation: The Pacific Plate has expanded Are seamounts that have built above sea level. Erosion by and moved over time. Older plates like the Izanagi, Farallon, waves destroyed the top of the seamount resulting in a and Phoenix plates were pushed beneath other plates in a flattened shape. Due to the movement of the ocean floor away from oceanic ridges, the sea floor gradually sinks and the flattened guyots are submerged to become undersea flat- divergence of tectonic plates during the assembly and topped peaks. disassembly of supercontinents Embryonic Ocean Basin (Stable Craton with a hotspot underneath) Stage A: At first, there is a stable Continental Craton, which has a hot Continental Rises spot just underneath. This warm hot spot Form as a result of three sedimentary processes: mass heats up the craton (continent) and causes it to swell wasting, the deposition from contour currents, and the upwards and in the breakup zone the continental crust gets vertical settling of clastic and biogenic particles. thinner and thinner and starts to crack, which eventually Continental Shelf causes the continent to break into two continents and a small ocean will with time form in the middle. The East Inorganic material built up as rivers carried sediment—bits African rift Valley is an example of stage A. of rock, soil, and gravel—to the edges of the continents and into the ocean. These sediments gradually accumulated in Juvenile Ocean Basin layers at the edges of continents. (Early Rifting of a Continent) Continental slopes Stage B: Now the Begin at continental shelf breaks. Continental slopes spreading of earth plates usually begin 1-5 kilometers above the ocean floor. starts and a small ocean Continental slopes are carved by gravitational slumping and has formed between the turbulent waters resulting in submarine canyons. newly broken up Continental slopes generally have a degree of incline continents. As the continents continue to drift apart, the between 1 and 10 degrees. edges of both continents will cool down and therefor get heavier and sink below the newly formed sea. This boundary is called a divergent boundary. The Red Sea is an example of stage B. Oceans basins are divided into 3 major provinces Mature Ocean Basin 1. continental margins (Full Ocean Basin) continental margin is the outer edge of continental crust abutting oceanic crust under coastal waters. It is one of the Stage C: Stage C, is three major zones of the ocean floor, the other two being when a large ocean has deep-ocean basins and mid-ocean ridges. formed between two continental margins 2. deep-oceans basins and spreading still In hydrology, an oceanic basin is anywhere on Earth that is occurs. A well developed mid ocean ridge has formed along covered by seawater. Geologically, most of the ocean basins the divergent boundary. The Atlantic Ocean is an example of are large geologic basins that are below sea level. stage C. 3. mid-ocean ridges Declining ocean basin A mid-ocean ridge is a seafloor mountain system formed by (Subduction Zone) plate tectonics. It typically has a depth of about 2,600 meters Stage D: At this stage, a and rises about 2,000 meters above the deepest portion of subduction zone has an ocean basin. This feature is where seafloor spreading formed and the ocean takes place along a divergent plate boundary begins to close up. One of the simplest ways a subduction zone forms is at the edge of a continent, where one tectonic plate is subdued below another tectonic plate. This is a convergent boundary and eventually the ocean will disappear and all that is left is a remnant ocean basin. The Evolution of ocean basins Pacific Ocean is an example of stage D. The WILSON CYCLE is a model that describes the opening Terminal Ocean Basin and closing of ocean basins and the subduction and (Closing Remnant Ocean Basin)  Stage E: At this stage, TECTONIC PLATES the continents are almost colliding. Plate/s from greek word plaka means "flat or surface" and Formation of magma Tectonics from greek word tektonikos means "movement". happens deep in the It is the study of movement, creation, and destruction of subduction zone and small mountains are building up. In the lithospheric (crustal) plates. subduction zone both metamorphism (change in the rocks composition), folding (the earth layers are “bending”) and It is dynamic means constant changing or occurring faulting (the earth crust cracks) occurs. The boundary is continuously over a period of time. convergent and the sea is at this stage narrow and irregular. An example of stage E is the Mediterranean Sea. Suturing Most geologists and geophysicists agree that plate movement is caused by the convection (heat transfer (Continental Collision) resulting from the movement of a heated fluid) of magma in Earth’s interior. Stage F: This is the final stage, before the PLATE BOUNDARIES mountain chain eventually will erode -The regions where two tectonic plates meet. down to a peneplain (that’s when the mountains have eroded -These boundaries are zones of intense geological activity, all the way down to the sea-level). At stage F, the two such as earthquakes, volcanic eruptions, and the creation of continents moving towards each other will collide and a mountains or ocean trenches, as the plates move relative to mountain chain forms. An example of this stage is the each other. Himalaya Mountains. TYPES OF PLATE BOUNDARY CONVERGENT - occur when plates move towards one This chapter describes the development and evolution of the another. ocean basins. Oceanic crust is much younger than most continental crust. Ocean basins form initially by the DIVERGENT - occur when two tectonic plates move away stretching and splitting (rifting) of continental crust and by from each other. the rise of mantle material and magma into the crack to form new oceanic lithosphere. Among the major ocean basins, the TRANSFORM - boundary that grind past each other without Atlantic has the simplest pattern of ocean-floor ages. going up or down. Subduction is confined to relatively small island arc systems Geological activity is about the processes that change the in the Caribbean and the extreme southwest. Thus, it is easy Earth’s surface and shape its structure. to reconstruct its successive stages. In contrast, both the Examples: volcanic eruptions, earthquakes, erosion, and the Pacific and Indian oceans are characterized by changes of movement of tectonic plates. spreading rate and direction and the development of new spreading axes. Because of these complications, it is difficult Geological features are the physical formations and to work out the changes in the shapes of these ocean basins. structures on the Earth's surface or within its crust created by geological processes. Examples: mountains, valleys, trenches, and cliffs. The Mediterranean can be classified as an ocean in the final stages of its life cycle—the only major remnant of the once extensive Tethys Ocean. The Mediterranean is shrinking as the African Plate continues to thrust its way northwards FOLDS - a geologic structure where rock layers are bent or beneath the European Plate. It is expected that the curved. Mediterranean would be floored by oceanic crust dating back Axial plane: Marks the middle of the fold. perhaps as far as Jurassic times, which would be consistent with its being the remnant of an old oceans and that it would Hinge line: Where the axial plane meets the Earth's surface. have an obvious major trench. Limbs: Parts on either side of the fold that stick out. GROUP 7 - HOW THE MOVEMENT OF PLATES LEADS TO THE FORMATION OF FOLDS, FAULTS, AND TRENCHES. TYPES OF FOLDS 1. Anticline: a fold that arches upward. The rocks dip away from the center of the fold. 2. Syncline: a fold where the rock layers are warped TWO MOST COMMON TYPES OF TRENCHES downward. Both anticlines and synclines are the result Subduction Trenches of compressional stress. 3. Monocline: A step-like fold with a steeper dip in These form at convergent plate boundaries where one otherwise gently sloping or horizontal rock layers. tectonic plate is being forced under another. 4. Dome: A structural feature where dips are radial and away from the center. This process often leads to the creation of deep oceanic 5. Basin: The counter part of dome where dips are trenches. (e.g., Mariana Trench) towards the center. Back-Arc Trenches FAULTS - Is a crack or fracture in the Earth’s crust that occurs These occur behind a volcanic island arc and can be formed due to the release of accumulated energy. as a result of complex tectonic interactions. When the tectonic plates that form the Earth’s surface move, they can slide past each other or collide, creating a fault. GROUP 8 - HOW THE MOVEMENT OF PLATES LEADS TO Faults are caused by stress. This stress is formed because of THE FORMATION OF VOLCANOES, REEF VALLEYS AND the immense amount of pressure that builds up between two MOUNTAIN RANGES blocks of rock. LITHOSPHERE - The lithosphere is the rigid outer layer of the TYPES OF STRESS Earth, consisting of the crust and the upper part of the COMPRESSIONAL STRESS - Occurs when two blocks of mantle. rock push toward one another. The movement of Earth's lithospheric plates TENSIONAL STRESS - occurs when two blocks of rock move - Movement of Earth's lithospheric plates, commonly referred away from one another. to as plate tectonics, involves the slow but constant motion SHEAR STRESS - Occurs when two blocks of rock slide past of large pieces of the Earth’s crust and upper mantle. This one another. movement is driven by forces within the Earth and occurs over millions of years, shaping the planet's surface. COMMON TYPES OF FAULTS WHY DO PLATES MOVE? 2 types of DIP-SLIP FAULT: Below the lithosphere is a layer called the mantle, which is NORMAL FAULT - happens when the block above the fault made of very hot, soft rock that flows like thick syrup. The moves down relative to the block below. These faults are heat from the Earth’s core causes this mantle to move in often found at divergent plate boundaries. circular patterns, known as convection currents. These currents push and pull on the plates above, causing them to REVERSE FAULT - the hanging wall moves up relative to the shift. footwall due to compressional forces, which cause the crust to shorten. These faults are typical at convergent VOLCANO - an opening in the earth’s crust through which plate boundaries. lava, volcanic ash, and gases escape. STRIKE-SLIP FAULT - occurs when the ground shifts Volcanoes form due to the movement of tectonic plate. horizontally along a nearly vertical crack, driven by horizontal Destructive Plate Boundary and Constructive Plate Boundary. shearing forces. (transform boundary) Constructive boundaries (divergent): Where plates are moving away from each other as new crust is created between the two plates. In California, San Andreas Fault is a famous example of a STRIKE-SLIP FAULT where two tectonic plates—the Pacific Destructive boundaries (convergent): Where plates are Plate and the North American Plate—slide past each other moving towards each other and old crust is either dragged down into the mantle at a subduction zone or pushed upwards to form mountain ranges. TRENCHES RIFT VALLEYS - an area where the earth's crust is splitting -Trenches are deep valleys in the ocean floor where one plate apart. of the Earth's crust slides under another. Rift valleys are elongated depressions formed by the tectonic -This movement pushes up mountains, causes earthquakes, activity of Earth's lithosphere, where tectonic plates move and creates volcanoes in the ocean and on land. apart, causing the surface to sink between faults. -These trenches are very deep, often more than 6,000 meters (about 20,000 feet). - Rift valleys form when tectonics plates beneath the Earth's surface diverge (or move away from one another in opposite directions). It is important to note here that rift valley formation, unlike rivers and glacial valleys, are solely created as a result of tectonic plate movement. MID OCEANIC RIDGE As tectonic plates move away from one another at mid- ocean ridges, molten rock from the mantle may well up and harden as it contacts the frigid sea, forming new oceanic crust at the bottom of the rift valley. This extensive chain of underwater mountain ranges is approximately 200 million years old and stretches 16,000 kilometers long. Separation of the Eurasian and North American plates, and the African and South American Plates, helped to create the Mid-Atlantic Ridge. Example: Mid Atlantic Ridge Continental rift Valley As the plate stretches and thins, the underlying asthenosphere flows upward and expands like a hot-air balloon, lifting the region to higher elevations. The continental crust breaks along faults, forming long mountain ranges separated by rift valleys. Example: Continental Rift Valley MOUNTAIN RANGES - a group or chain of mountains located close together. Mountains are usually formed at what are called convergent plate boundaries, meaning a boundary at which two plates are moving towards one another. This type of boundary eventually results in a collision. Mountains form where two continental plates collide. Since both plates have a similar thickness and weight, neither one will sink under the other. Instead, they crumple and fold until the rocks are forced up to form a mountain range. As the plates continue to collide, mountains will get taller and taller. Example: Himalayas Mountain ranges