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Earth-Science.docx
- 1. Earth Science Plate Tectonics 4layers Inner crust Outer crust Mantle Crust Crust Outermost layer of Earth and made up of rocks Extends to 32km-72 km below Lithosphere Consists of crust and upper mantle Earth Atmosphere Hydrosphere Lithosphere Characteristics of Continental & Oceanic Crust Continental Crust Oceanic Crust Made up of silicon, oxygen and aluminum, calcium, sodium, and potassium Found under the ocean floor 35-40km thick 7-10km thick, average of 8km thick Made up of less dense rocks called granite Made up of a dense rock called basalt Density of 2.7 g/cm^3 Density of 2.9 g/cm^3 Younger Older Tectonic Plates Theory which states that lithosphere is divided and constantly moving. Basis for dividing Fault lines Geological Activities Major Plates Minor Plates Eurasian Plate Caribbean Plate North American Plate Philippine Plate South American Plate Nazca Plate Australia-Indo Plate Arabian Plate Pacific Plate Juan de Fuca Plate African Plate Scotia Plate Antarctic Plate Cocos Plate Locating Earthquake Epicenter using Triangulation Method Earthquake Result or movement of plates Shaking of earth’s crust caused by the release of energy Epicenter is above the focus Focus is where the rupture starts Seismic Waves Waves of energy caused by the sudden breaking of rock within the earth or an explosion 2 types Body Waves Surface Waves
- 2. Body Waves Travelsthrough the interior of the Earth Examples: P Waves S Waves Surface Waves Travels through the crust Examples: L Waves (Love Waves) R Waves (Rayleigh Waves) Speed Hierarchy P Waves S Waves L Waves R Waves Seismograph Instrument that detects earthquakes Epicentral Distance d= td/8 sec x 100 km Triangulation Method 1. Check the scale on your map 2. Determine the distance to the epicenter on your map 3. Draw a circle with a radius equal to the number you acquired 4. Do the same for distance to the epicenter that the other seismographs recorded 5. All the circles should overlap. The point where all the circle overlap is the approximate epicenter of the earthquake Measurement starts at discrepancy, whether it may be a downward or upward amplitude Distribution of Earthquake Epicenters, Active Volcanoes, and Mountain Ranges Earthquake Locations Found along the edges of the continents Mid-Continents Oceans Places with no earthquakes Northernmost Area Majority of Europe Western Part of Africa Eastern Portion of North and South America Volcanoes are found Edges of some continents East & South Asia Western Coast of North & South America Conclusion Earthquake Epicenters and Volcanoes are located in the same place Plate boundaries vary in Mountain Ranges Mountain Ranges are located in some plate boundaries Lithosphere Division Geological Activity in the Location
- 3. Relation of Locationof Epicenters, Active Volcanoes, and Mountain Ranges Located at the plate boundaries Effects of movement of plates Locations of these form plate boundaries Importance to know location Avoid extensivity of probable damage Become more proactive Plate Boundaries Stress Force acting on the unit area of a material Fault Break in the earth’s crust where significant movement has taken place Stress Fault Plate Boundaries Compressional Reverse Fault Convergent Tensional Normal Fault Divergent Shear Stress Strike Slip Transform Plate boundaries are systems of faults. All plate boundaries are faults, but not all faults are plate boundaries. 2 Reasons 1. Not all faults are located in the plate boundaries 2. Not all plate boundaries are active/inactive Plate Tectonics Movement of the lithosphere Boundary Types Transform/Strike Slip Where plates move horizontally against one another Divergent/Constructive Where plates move away from each other Convergent/Destructive Plates press into one another Plates that move with one another Boundary Magnitude Depth Transform <8 <25 km Divergent <6 <10 km Convergent <9.5 <0-700 km Types of Convergent Subductions Ocean Plate-Ocean Plate Older Oceanic Plate subducts They form: Island Arcs Ocean Trench Continental Plate-Continental Plate Mountains Plateau Oceanic Plate-Continental Plate They form Volcanic Island Arcs, which are chains of volcanoes that are parallel to a trench Continental Plate-Continental Plate No subduction occurs Mountains are formed Crust is pushed upwards
- 4. Divergent/Constructive Magma coolsdown, becomes part of the crust and diverges the plate boundaries Plates diverge 3-10 cm per year Creates the following New crusts Mid-Ocean Ridge Rift Valley Transform/Conservative Contact between 2 plates that slide, which is caused by plate divergence They create huge earthquakes/fault systems Earth’s Mechanisms -Alfred Lothar Wegener (1880-1930), proposed the Continental Drift Theory 2 reasons why it wasn’t accepted by then Couldn’t find the reasons why the plates move Wegener was a meteorologist Asthenosphere Part of the upper mantle Differ from lithosphere, due to temperature Viscoelastic Mantle Convection Proposed by Arthur Holmes Holmes theorized that convection currents move throughout the mantle the same way heated fluids circulate in a room. Slab Pull Theory Slab is pulled down from the mantle, it drags the rest of the plate along with it causing tectonic the movement of tectonic plates A very dense slab sinks faster because of the gravitational pull Ridge Push Due to the elevated position of the oceanic ridge, which cases the slabs of the lithosphere to slide down the flanks of the ridge Proposed by Bott, 1991 Continental Drift Theory Created by Alfred Wegener Earth was once a huge landmass called Pangaea, which is a Greek term for “all earth” The theory had 4 main pieces of evidence 1. Apparent Fit of the Continents 2. Fossil Correlation 3. Rock & Mountain Correlation 4. Paleoclimate Data Coal remains are found in the cold regions of Earth, coal remains are the fossil remains of tropical plants which can’t survive cold temperatures Glossopteris fossil is found in Australia, Antarctica, India, South Africa, and South America—all the southern continents. Lystrosaurus fossils are only found in Antarctica, India, and South Africa. Cynognathus was as large as a modern wolf. Its fossils are found only in South Africa and South America. Mesosaurus and its remains are found solely in South Africa and Eastern South America.
- 5. Seafloor Spreading Proposedby Harry Hess Mantle is responsible for the movement of the continents Evidences 1) Molten Material Found pillow lava Can only form when molten material hardens quickly after erupting under water 2) Drilling Samples Tested the age of the rock, the farther away the rocks are from the mid- ocean ridge the older they are 3) Magnetic Stripes When magnetic field is reversed, the iron faces the opposite direction. Which forms stripes. Caused by the magnetic material (iron) found in the magma, solidified lava aligns themselves. Earth’s magnetic field reverses every millions of years, which causes the reversal or pattern of the solidified lava. Magnetic stripes are represented by color Whatever polarity is found in the youngest rock, it’s the normal polarity. The iron found in the solidified lava acts like a compass Findings of Seafloor Spreading a) Rocks are younger near the ridge b) Older rocks are farther away from the ridge c) Sediments are thinner at the ridge d) Rocks at the ocean floor are younger than those at the continents Differences of Seafloor Spreading and Continental Drift Continental Drift Continents move through unmoving oceans Seafloor Spreading Ocean is the actual site for tectonic activity