2The Composition of the Earth The Crustoutermost layer of the Earth5 to 100 km thickthinnest layerThe Mantle- layer of the Earth between the crust and the core- much thicker than the crust-contains most of the Earth’s mass
3The Composition of the Earth The Core- layer of the Earth that extends from below the mantle to the center of the Earth- made mostly of iron
5The Physical Structure of the Earth Five Physical Layerslithosphere: crust & upper rigid mantleasthenosphere: plastic layer of mantle on which the tectonic plates movemesosphere: strong lower part of the mantle (below asthenosphere to the outer core)
6The Physical Structure of the Earth outer core: liquid part of the core, below the mantle and surrounds the inner coreinner core: solid dense center of our planet
9Tectonic Plates lithosphere = a jigsaw puzzle tectonic plates = the piecesconsist of both oceanic crust and continental crustThey “float” on the asthenosphere
10Mapping the Earth’s Interior seismic waves = vibrations produced by an earthquake-travel at different speeds depending on the density & composition of material they pass throughseismographs: measure the times at which different seismic waves arrive and record the differences in their speeds* calculate the density and thickness of Earth’s layers
11Wegener’s Continental Drift Hypothesis Continental drift: the hypothesis that states that the continents once formed a single landmass, broke up, and drifted to their present locations.Evidencefossils of plant & animal speciessimilar rockssame ancient climateALL found on continents that are far apart
12* a single huge continent Pangaea* a single huge continent* existed about 245 million years ago* split into two large continents— Laurasia and Gondwana about 180 million years ago.* ~65 million years ago split into smaller pieces
18Evidence for Sea-Floor Spreading Mid-ocean ridges: places where sea-floor spreading takes place* magma rises toward the surface and solidifies forming new oceanic lithosphereEvidence for Sea-Floor SpreadingMagnetic Reversals: when Earth’s magnetic poles change places* recorded over time in oceanic crust
25Three Tectonic Plate Boundaries Convergent Boundaries : when two tectonic plates collideA. continental-continental : pushescontinental crust upward (mountain ranges)Subduction Zones (crust is recycled)B. continental-oceanic: denser oceaniccrust gets pushed downinto the asthenosphereoceanic-oceanic: one of the oceanic plates is subducted
28*most found on the ocean floor Divergent Boundaries : when twotectonic plates separate*mid-ocean ridges (new crust formed)Transform Boundaries : when twotectonic plates slide past each other horizontally*most found on the ocean floor
30Mid-Atlantic Ridge splitting Iceland and separating the North American and Eurasian Plates.
31San Andres FaultThe San Andreas fault zone slices through two thirds of the length of California. Along it, the Pacific Plate has been grinding horizontally past the North American Plate for 10 million years, at an average rate of about 5 cm/yr. Land on the west side of the fault zone (on the Pacific Plate) is moving in a northwesterly direction relative to the land on the east side of the fault zone (on the North American Plate).
34Possible Causes of Tectonic Plate Motion changes in density within the asthenosphere caused by thermal energy from deep within the Earth1. Ridge-push: due to gravity thelithosphere is pulled under2. Slab- Pull: denser oceanic crust sinks and pulls the rest of the plate with it3. Convection: hot rock rises, then cooler rock near the surface sinks = cycle
36Convection CurrentsConvection currents in the mantle carry the plates of the lithosphere like a conveyor belt.
37oldest continental crust ~ 3.8 billion years old Because ocean floor is continuously created at mid-ocean spreading centers, it is far younger than most continental rock.oldest continental crust ~ 3.8 billion years oldoldest oceanic crust ~ 150 million years oldSpreading rate of the Atlantic Ocean:~ 25 mm/yr
38Tracking Tectonic Plate Motion Tectonic plate movementsslow and gradualcan’t see or feel them movingmeasured in centimeters per year (cm/yr)(GPS) global positioning system : a system of satellites used to measure the rate of tectonic plate movement
41Compare the mountains in the photographs Compare the mountains in the photographs. Write a description of each mountain, and suggest how it might have formed. Do you know where these various types of mountains are found in the world? Have you ever visited any of them? Would it ever be dangerous to study them?Record your responses in your science journal.
43Objectives Describe two types of stress that deform rocks. Describe three major types of folds.Explain the differences between the three major types of faults.Identify the most common types of mountains.Explain the difference between uplift and subsidence.
44DeformationDeformation : the process by which the shape of a rock changes because of stresstypes of stressCompression : occurs when an object is squeezed = when two tectonic platescollideTension: occurs when forces act to stretch an object
45bending of rock layers because of stress in the Earth’s crust Foldingbending of rock layers because of stress in the Earth’s crustdifferent typescan be large or small
47result of compressional stress Anticline foldresult of compressional stressSyncline fold
48Synclinal folds in bedrock, near Saint-Godard-de-Lejeune, Canada
49Faulting a break in a rock where one rock slides relative to another Normal FaultsReverse FaultsStrike-Slip FaultsAnimations of Faults
50Plate Tectonics and Mountain Building Folded Mountains - form when rock layers are squeezed together and pushed upwardFault-Block Mountains - form when tension causes large blocks of the Earth’s crust to drop down relative to other blocksVolcanic Mountains – forms when rock is melted in a subduction zone = magma, which rises to the Earth’s surface and erupts
51Other Types of Mountains Dome Mountains -formed when melted rock pushes its way up under earthBlack Hills, South Dakota & Adirondack Mountains, (NY)Residual Mountains are mountains that are really plateaus that have worn down from erosion
54Most common type on land Folded mountainsMost common type on landAppalachian Mountains (eastern North America)- oldUrals (Russia)- old (200 my)Alps mountains (southern-central Europe)Himalayan mountains (southwest Asia)- young Rockies mountains (western N.A.)- young (10-25 my)Fault- Block mountainsForm along faultsTeton Range (Wyoming)Sierra Nevada mountains = largest in theUS
55Volcanic Mountains Andes mountains (western coast of South America)Cascade Range (runs south from British Columbia, Canada, through the U.S. states of Washington and Oregon before it becomes the Sierra Nevada mountain range in northeastern California)
56when the lithosphere becomes stretched in rift zones Uplift and SubsidenceUplift: when rocks rise when a weight isremoved from the crustSubsidence: when rocks sink becauseas they cool they become denserorwhen the lithosphere becomes stretched in rift zones