Layers of the Earth PDF

Layers of the Earth Compositional Classifies the layers of the Earth based on the chemical composition of each layer Crust - egg shell - thinniest - rigid - 3-5 miles (8 km) Mantle - egg whites -...

Layers of the Earth Compositional Classifies the layers of the Earth based on the chemical composition of each layer Crust - egg shell - thinniest - rigid - 3-5 miles (8 km) Mantle - egg whites - thickest - hot - silicate rocks (Fe and Mg) - forms connective currents - Upper Mantle: lower temperature, lower pressure, solid - Lower Mantle: higher temperature, higher pressure, liquid Core - the yolk - center of the Earth - makes up 15% of Earth's volume - consists of Iron, Nickel, and Sulfur Mechanical Classifies the layers of the Earth based on their physical properties Lithosphere - outermost part - most rigid - made up of crust and upper mantle - 8 - 32 km - 32 - 932 °F (0 - 500 °C) - Continental ➔ older and thicker ➔ found under land masses ➔ less dense ➔ average density: 2.7 g/cm³ ➔ 25 - 70 km ➔ composed of old rocks, mainly Granite - Oceanic ➔ younger and thinner ➔ found in the ocean floor ➔ 7 - 10 km ➔ denser ➔ average density: 3 g/cm³ sevizcaya | 10 - Mende  ➔ will always subduct during continental to oceanic convergence ➔ made up of mainly basaltic rocks Asthenosphere - has a consistency like butter - comprises the upper mantle - semi-solid - 100 - 180 km (110 mi) - 2,732 °F (1,500 °C) - flows easily, rigid Mesosphere - comprises the lower mantle - flows slower than Asthenosphere - 2,200 km - Outer Core: ➔ true liquid ➔ responsible for Earth's magnetic field ➔ 2,900 km ➔ 8,132 - 9,932 °F (4,500 °C - 5,500 °C) - Inner Core: ➔ 10% of magnetic energy ➔ generates the Earth's magnetic field ➔ solid ➔ responsible for movements in the outer core ➔ 1, 221 km ➔ 7000 °C (12,632 °F) Discontinuity All those layers are separated from each other through a transition zone. These transition zones are called discontinuities. Conrad(Conorod) - between upper and lower crust Mohorovicic - between lower crust and upper mantle Repiti - between upper and lower mantle Guttenberg - between lower mantle and outer core Lehmann - between outer and inner core Plates Plate Tectonics framework that explains how and why several features of the Earth continuously change sevizcaya | 10 - Mende Plate Boundaries lies between plates (2 or more plates) Different Types of Plates Primary Plates (Major) larger (size about 20 million km²) 7 Primary Plates - Pacific - North American - Eurasian - African - Antarctic - Australian - South American Secondary Plates (Minor) smaller, about 1 km 8 Secondary Plates - Juan de Fuca - Nazca - Cocos - Caribbean - Philippine - Arabian - Indian - Scotian Microplate smaller than secondary plate Basis of Dividing Plates looking into geological features and events distribution of earthquake epicenters, volcanic activities, major mountain ranges of the world Earthquake - Seismic Waves Earthquake shaking or trembling caused by the sudden release of energy occur when rocks along a fault suddenly move What causes earthquakes? sevizcaya | 10 - Mende  - Tectonic plates are always slowly moving, but gets stuck at their edges due to friction. - 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. Stress force that squeezes rocks together, stretches or pulls them apart, or pushes them in different directions tectonic plates move: causes stress in the crust, produces faults and folds Faults a break in the Earth's crust along which significant movement has taken place Philippine Fault Zone - Bangui Fault - Digdig Fault - Infanta Fault - Guinayangan Fault - Sibuyan Sea Fault - Masbate Fault - Central Leyte Fault - Lianga Fault - Eastern Mindanao Fault - Mati Fault How do Faults produce Earthquakes? Three Types of Faults Normal Fault - result of tension - rock layers in the Earth's crust are pulled apart » gravity causes one section to move downward in relation to the other Reverse Fault - result of compression - rock layers in the Earth's crust are squeezed together » force pushes one section upward in relation to the other Strike-Slip Fault - forms when the rock layers on opposite sides of a fault slides past each other horizontally sevizcaya | 10 - Mende  - sometimes called as tear, wrench, or transcurrent fault How do Faults produce Earthquakes? 1. Energy from inside the Earth makes the ground move. 2. No movement friction right away because of FRICTION. 3. Friction held the rocks together. 4. Once friction is overcome, the ground will move and the earthquake will occur. Everytime a FAULT slips or moves, the Earth QUAKES. Epicenter the location on the surface of the earth directly above the focus Focus/Hypocenter point within the earth where energy is released Magnitude number that characterize the relative size of an earthquake measured using a seismograph Intensity measures how strong the shaking is due to an earthquake (Roman Numerals) can be determined by its effects on people, infrastructure, and the environment Seismograph instrument used to record the motion of the ground during an earthquake Seismometer internal part of the seismograph may be a pendulum or a mass mounted on a spring Seismogram recording of the ground shaking at the specific location of the instrument - Horizontal Axis - time(s) - Vertical Axis - ground displacement (usually mm) Richter Scale based on measurement of the times and amplitudes of seismic waves by certain seismograph sevizcaya | 10 - Mende Moment Magnitude Scale gives measure of the amount of energy released by an earthquake Modified Mercalli Scale rates the effects of earthquakes ranges from 1-12 based on observations of the intensity of the ground shaking and damage in the areas affected by an earthquake Seismic Waves energy released from an earthquake that are generated by tectonic plate movements move out in all directions from the focus rocks break and move » PE is transformed to KE in form of Seismic Waves recorded by seismographs Body Waves - Travel through the earth's interior - "reflect" off different types of rocks in different ways - allows seismologists to identify different rock present in Earth's crust and mantle far beneath the surface - Seismic reflections: used to identify hidden oil deposits deep below the surface - From the focus Primary Wave (P-Wave/Pressure Waves) ➔ Fastest ➔ Longitudinal - left to right ➔ can move through solid rocks, fluids, and gases ➔ Direction of Propagation: parallel to the particle motion ➔ 8 km per sec ➔ 1st movement felt ➔ formed by compressions ➔ led to the discovery that the lower mantle is in liquid state Secondary Waves (Shear Waves) ➔ after P-Wave ➔ Transverse - up and down ➔ Can only move through solids ➔ Direction of propagation: Perpendicular to the particle motion ➔ 4.5 km per sec ➔ Causes more building damage Surface Waves - propagates along the interface of the earth - from the epicenter Love Waves ➔ named after A.E.H. Love sevizcaya | 10 - Mende  ➔ fastest surface wave ➔ side-to-side horizontal motion Rayleigh Waves ➔ named after Lord Rayleigh ➔ rolling waves ➔ rolls along the ground, lake, or an ocean Triangulation Method technique used by scientists to pinpoint the earthquake epicenter uses distance information determined from 3 seismic stations, where circles are drawn around each station on the map resulting interaction of the circles in the approximate location of the epicenter Things needed: map writing materials calculator compass data of time difference in the arrival time of P-Waves and S-Waves Steps: sevizcaya | 10 - Mende  1. Create a data table and list the P-Wave and S-Wave arrival time recorded by the seismograph of the different stations. 2. Calculate the lag time/time difference of each station. Lag time = S-Wave arrival time - P-Wave arrival time 3. Calculate the distance from the station to the event. 4. Convert the distance of km to cm using the scale provided by the map (will be the radius). 5. Draw the 3 circles and an intersection should come out. 6. Mark the epicenter. What is the importance of determining the location of the Earthquake Epicenter? pinpoints active fault lines early evacuation Some terminologies Geology Branch of Science that deals with the study of the planet Geologists Scientists who study the Earth; its history, nature, materials, and processes Seismologists studies the internal structure of the Earth tries to determine factors that contribute to or foretell an earthquake Plate Boundaries lies between plates (2 or more plates) sevizcaya | 10 - Mende Convergent Plate Boundary a boundary where two plates move together. occurs when two tectonic plates push together(lithospheric.plates) Also called as collision or destructive boundary Forms oceanic trench, volcanism, island formation, and in some cases, earthquakes and mountain ranges. Processes along Convergent Boundaries: Convection Currents - heat can be transferred from.one place to another - fluids expand and become less dense when heated - heated mantle material rises from deep inside the mantle; cooler mantle material sinks (warm fluid up, cool fluid down) Slab Pull Theory - crustal plate moves further; cools and becomes increasingly dense ➔ causes it to sink beneath the continental crust in a subduction zone Pacific Plate (w/ subduction zone) is destroyed at a faster rate than North American Plate (w/o subduction zone) sevizcaya | 10 - Mende  - the weight of the sinking, cooling plates cause a major pulling action which causes the rest of the plates to be pulled downwards as well ➔ also pulled down by gravity ➔ melts and gets combined with magma ➔ Convection Current happens and new lithosphere is created ➔ is now widely accepted as - plate pulled by the weight of its cold, dense subducting section Types of Convergence Oceanic-Oceanic Convergence - Two oceanic slabs converge and one descends beneath the other (subduction) - cooler, denser, older plate sinks beneath warmer, less dense, newer plate - Geological process/features: island volcanic arcs, trenches, earthquakes Island Volcanic Arc ➔ A chain of islands that form as a result of volcanic activity when one tectonic plate slides underneath another Examples: ➔ Aleutian Islands - line of volcanoes in Alaska where the Pacific Plate is being subducted under the North American Plate ➔ Philippine Trench sevizcaya | 10 - Mende ➔ Mariana Trench sevizcaya | 10 - Mende  ➔ Philippine Island Arc ➔ Indonesian Archipelago ➔ Japan Island Arc ➔ Indonesia Island Arc ➔ Manila Trench ➔ Negros Trench ➔ Philippine Trench ➔ Cotabato Trench ➔ Sulu Trench Oceanic-Continental Convergence - Denser oceanic lithosphere sinks into the asthenosphere (subduction) - Geological process/features: deep ocean trenches, volcanoes, mountain ranges, fault lines, continental volcanic arc, earthquakes Examples: ➔ Andes Mountains in South America - collision of the oceanic Nazca Plate and the continental South American Plate ➔ Peru-Childe Trench - Nazca Plates subducting beneath the continental crust of the South American Plate sevizcaya | 10 - Mende  ➔ Cascade Range - Juan de Fuca Plate subducting beneath the edge of North America Continental-Continental Convergence - no subduction happens - Geological process/features: mountain ranges (including volcanic cones), plateaus, valleys, earthquakes Examples: ➔ Himalayas Mountain Range and Tibetan Plateau - collision between the Indian Plate and Eurasian Plate ➔ Sierra Madre ➔ Mount Everest Divergent Plate Boundaries sevizcaya | 10 - Mende  a place where two plates move apart constructive or extensional boundary forms seafloor/oceanic ridges, and continental rift zones/rift valleys earthquakes are common and magma rises from the Earth's mantle to the surface, solidifying to create new oceanic crust Old Plates New Plates pushed opening of lithosphere cool hot denser less dense heavier lighter Tension - tensional stress (stretches and pulls rocks apart) Rift Valleys - deep faulted structures found along the axes of divergent plate boundaries Mid-ocean ridge - most extensive chain of mountains on Earth, stretching nearly 65,000 kilometers (40,390 miles) and with more than 90% of the mountain range lying in the deep ocean Types of Divergence Continental-Continental Divergence a continent separates into two or more smaller continents when it is ripped apart along a series of fractures Rift/Rift Valleys becomes sea or ocean over time Examples: 1. Red Sea Rift - the spreading center between the African Plate and the Arabian Plate 20 million years ago - one of the youngest bodies of water; still growing, which will eventually separate the continents of Asia and Africa 2. West Antarctic Rift sevizcaya | 10 - Mende  - north-trending continental rift zone after the Pacific Phoenix Plate subducted beneath the Antarctic Plate 200 million years ago - separates the Colorado Plateau in the west from the interior of the North American craton in the east 3. Baikal Rift Valley - result of the American Plate slowly tearing itself away from the Eurasian Plate for about 25 million years - one of the deepest active rifts on Earth 4. East African Rift - Somali Plate and Nubian Plate Oceanic-Oceanic Divergence two oceanic plates move apart which will take the form of long, wide swiells along the ocean floor happens in the ocean at mid-ocean ridges; lava rises upward, erupts, and cools, then later, more lava erupts and pushes the original seafloor outward forms ocean ridges and seafloor spreading Examples: 1. Mid-Atlantic Ridge - divergent motion between the Eurasian and North American and African and South American Plates - discovered in the 1950s - led scientists to form the theory of seafloor spreading and general acceptance of Wegener's theory of Continental Drift 2. Iceland - sits on a volcanic hotspot where it is the only place that the Mid-Atlantic Ridge manifests itself above sea level - not due to magma builduo along the ridge alone 3. East Pacific Rise - a mid-ocean ridge - a divergent tectonic plate boundary located along the floor of the Pacific Ocean - separates the Pacific Plate to the west from the North American Plate, the Rivera Plate, the Cocos Plate, the Nazca Plate, and the Antarctic Plate 4. Southwest Indian Ridge - separates the Somali Plate to the north from the Antarctic Plate to the south sevizcaya | 10 - Mende Transform Plate Boundaries Two plates grind against each other w/o the production or destruction of the lithosphere two tectonic plates slide horizontally past each other conservative boundary or strike-slip boundary no magma, no volcano, no rift valley, but lots of earthquakes when the plates move back to original formation, pressure builds up and earthquake can occur Shear Stress - force tending to cause deformation of a material by slippage along a plane or planes parallel to the imposed stress Example: San Andreas Fault - Pacific Plate (NW) and North America Plate (SE) sevizcaya | 10 - Mende  Continental Drift Theory Alfred Wegener in 1912 a Meteorologist and Astronomer Widely credited for the theory because he was the first one to write a detailed and comprehensive story states that the continents were once united into a single supercontinent called Pangaea(Pan: all, entire, whole; Gaea: earth, land; Pangaea: All earth/All land in Ancient Greek) suggested that Pangaea broke up a long ago and that the continents then moved to their current positions Hole in 1 continent is present in another Timeline of the Continents 245 MYA Pangaea existed when some of the earliest dinosaurs were roaming. Surrounded by a sea (Panthalassa - "All sea") 180 MYA Pangaea broke into 2 big pieces Laurasia (northern part) and Gondwana(southern part) ➔ most recent suoercontinents before the continents separated ➔ late Paleozoic and early Mesozoic era 65 MYA by the time dinosaurs became extinct, Laurasia and Gondwana split into smaller pieces MYA = Million Years Ago Pangaea Ultima or Pangaea II is a possible future supercontinent configuration Evidences of Continental Drift Theory 1. Apparent Fit of the Continents Certain continents have shapes that fit each other like puzzle pieces It implies that those partner continents were once a single landmass which broke apart later on Alexander von Humboldt ➔ German geographer ➔ 1800's: noticed the similarity in the coastlines of South America and Africa; "continents bordering the Atlantic Ocean were once connected" 2. Fossil Correlation sevizcaya | 10 - Mende  Some fossils preserved in rocks are a match but are discovered on different continents, suggesting that the same species of animals are separated by the drift Antonio Snider-Pellegrini ➔ French scientist ➔ presence of two identical plant fossils in North America and Europe Frank B. Taylor ➔ American geologist ➔ 1908: proposed Continental Drift as a mechanism for the origin of mountain belts due to continental collision eg. ➔ Mesosaurus (a freshwater reptile) and Glossopteris (a plant) remains in South America, Asia, Australia, and Africa ➔ Cynognathus (dog jaw) in South America, Africa, Antarctica, and Australia ➔ Lystrosaurus in Africa, India, and Antarctica 3. Rock and Mountain Correlation Ages and typed of rocks and mountains from different continents also match eg. ➔ May rocks from Argentina and South Africa, diamond-like rocks in South America and Brazil ➔ Appalachian Mountains (North America) and Scottish Highlands, Karro Systems (South Africa) and Santa Catarina System (Brazil) 4. Paleoclimate Data Post climate data Heavy glaciers carve grooves called striations/striae (scratch marks) on the rocks as they drift across the land eg. ➔ Glaciers melt and move when hot, and it drag rocks along their bottom which causes abrasion (Africa, India, some part of America and Asia) ➔ Coal beds and Deposits (which are only formed from organic matter like dead plants and animals) are found under Antarctica, indicating that the freezing lifeless Antarctica was once inhabited by many types of plants and animals sevizcaya | 10 - Mende  Seafloor Spreading a geologic process ocean floor moves like a conveyor belt tectonic plates split apart from each other ➔ older plates are pushed by new plates to the subduction zone ➔ new ocean floor forms along cracks in the ocean crust as molten material erupts from the mantle pushing older rocks to the sides keeps the shape of the earth Harry Hammond Hess American geologist and a US Navy Officer (WW2) Proposed seafloor spreading theory to account for continental movement in 1962 suggested that continents do not move across oceanic crust, rather continent and oceanic crusts move together "The seafloor separates at oceanic ridges and then new crust is formed by upwelling magma." Robert Dietz American geophysicist and oceanographer Discovered the first fracture zone in the Pacific which he related to deformation of the Earth's crust. ➔ led him to hypothesize that new crustal material is formed at oceanic ridges and spreads outward at a rate of several centimeters per year Drummond Matthews British marine geologist and geophysicist Key contributor to the theory of Tectonic Plates Noticed there was a symmetrical pattern of magnetic stripes on either side of the mid ocean ridges (magnetic stripes) Recognized for both seafloor and plate tectonics theory Seafloor Spreading Theory proves that the ocean itself is a site of tectonic activity was proposed by Harry Hess and Robert Dietz ➔ They wanted to know how the mid ocean ridges form and why the rocks were younger in the ocean crust when compared to the continental crust. ➔ They explored the part of the Earth where Wegener had not ventured using Sonar ❖ sound navigation and ranging sevizcaya | 10 - Mende  ❖ technique that uses sound propagation to navigate, communicate, measure distances, and detect objects on or under the surface of the water ❖ during WW2, battleships and submarines carried echo sounder ★ produce sound waves that travel outward in all directions ❖ used to map the ocean floor ➔ Seafloor Bathymetry ❖ study of the beds or floors of water bodies ❖ scientists studied the Mid-Atlantic Ridge ❖ ocean floor is younger than continental plate Seafloor Spreading Evidence 1. There are active fractures in the lithosphere along the ocean floor, in a pattern that mimics the shapes of the continental coastlines. 2. The age of the seafloor rock increases as you get further away from the mid-ocean ridge. Age of Rocks ➔ age, density, and thickness of the oceanic crust increase with distance from the mid-ocean ridge ➔ rocks are younger at the mid-ocean ridge ➔ Sediments - thinner near the ridge 3. The thickness of the layer of sediments deposited on the ocean floor increases as you get further away from the mid-ocean ridge. 4. Patterns of seafloor magnetism on either side of mid-ocean ridges match up with one another. Magnetic Patterns/Magnetic Reversals ➔ Magnetic polarity in the seafloor is normal at mid-ocean ridges ❖ but reversed in symmetrical patterns away from the ridge center due to the bands of cooled lava continues across the seafloor ➔ magnetic flip of the earth ➔ north pole becomes south pole and vice versa ➔ due to change in the direction of flow in the outer core ❖ affects polarity of the planet ➔ lava solidifies → iron bearing minerals crystalize → minerals behave like tiny compasses sevizcaya | 10 - Mende  Plate Tectonics Theory Summary of continental drift theory, seafloor spreading theory, and seismicity (earthquakes) study of how earth's crust is shaped by geological forces Plate Tectonics Theory states that.. 1. Lithosphere is broken into plates. 2. The plates float on the asthenosphere beneath the lithosphere. 3. Convection currents in the Asthenosphere drive plates motion. 4. Plates move along boundaries (Plate Boundaries) Stress is the force applied to a rock and may cause deformation. Mechanism of Plate Tectonics 1. Convection Currents This convection circling within the mantle push the magma up forming new crust, and exerting lateral force on the plate, pushing it apart to create seafloor spreading. heat can be transferred from one place to another fluids expand and become less dense when heated heated mantle material rises from deep inside the mantle; cooler mantle material sinks now largely out of favor, with modern imaging techniques unable to identify mantle convection cells that are sufficiently large to drive plate movement Mantle Convection Theory ➔ Arthur Holmes (1930) ➔ hot rocks, less dense goes up; cold rock, more dense goes down 2. Slab Pull Theory Strong force that drives subducting tectonic plates The weight of the tectonic plate drives subduction in oceanic crust crustal plate moves further → cools and becomes increasingly dense ➔ causes it to sink beneath the continental crust in a subduction zone ➔ the weight of this sinking, cooling plates cause a major pulling action → causes the rest of the plates to be pulled downwards as well ❖ also pulled down by gravity ❖ melts and gets combined with magma ❖ convection current happens and lithosphere is created ❖ is now widely accepted ➔ plate pulled by the weight of its cold, dense subducting section sevizcaya | 10 - Mende  3. Ridge Push occurs at mid-ocean ridges as the result of the rigid lithosphere sliding down the hot, raised asthenosphere below mid-ocean ridges Martin Harold Phillips Bolt - "The pushing on the plates is due to the difference in gravitational potential energy between a plate at its spreading center and subduction zone." plate pushed by the weight of the mid-ocean ridge If slab pull is not the main plate driver, ridge push is another possibility. lithosphere formed at divergent plate margins is hot and less dense than the surrounding area → sinks to form oceanic ridges ➔ newly formed plate slides sideways off the high areas; pushing the plate in front of them resulting in a ridge-push mechanism John Tuzo-Wilson Canadian geophysicist was possible because of the new information about the nature of ocean floor, magnetism, and flow of heat from earth's interior with the distribution of volcanoes, earthquakes, and fossils 1963: proposed that plates might move over fixed "hotspots" in the mantle, forming volcanic island chains like Hawaii ➔ Earth's crust is made of pieces of rock called Tectonic Plates sitting on the molten interior of the planet 1965: idea of third type of plate boundary - Transform Faults sevizcaya | 10 - Mende