11Outer Core Layer of molten material Covers the inner core 2,250km thick
12Inner Core Dense solid ball of metal Extreme pressure does not allow Fe & Ni to spread out to form liquid1,200km thick
13What are the 3 ways that heat is transferred? RadiationConductionConvection
14Radiation Heat transferred by EM waves through space EX: Sitting by the fire!
15Conduction Heat transferred through direct contact EX: Spoon in hot chocolate
16ConvectionHeat transferred through a fluid movement of either a gas or liquidEX: Chicken noodle soup heating on the stove!
17Which of these do you think happens in Earth’s mantle? Convection!Convection currents flow in the asthenosphereHeated material rises to the top of the mantle (lithosphere), cools, then sinks back to the bottom
21Scientific Method Problem/Question Research Hypothesis Experiment AnalyzeConclude
22Supporting Evidence of Wegener’s theory LandformsFossilsClimate
23Landforms South America & Africa have similar mountain ranges Europe & North America have similar coal fields
24FossilsFossil-any trace of an ancient organism that has been preserved in rockMesoaurus fossils have been found in places now separated by oceansGlossopteris (fern like plant) fossils have been in rocks in Africa, South America, Australia, India, & Antarctica
25ClimateSpitsbergen Island lies in the Arctic Ocean, north of Norway, covered with iceFossils of tropical plants have been discovered under the ice!South Africa-deep scratches in rock indicate glacier movement there!!!
27REJECTED!!! Scientists rejected Wegener’s theory of continental drift Most scientists in the 1900’s believed the Earth was cooling & shrinking causing the continents to move & mountains to form
28Is sea-floor spreading like continental drift? 1960Harry Hess, when studying the mid-ocean ridge, proposed that the ocean floor moved like a “conveyer belt” moving the continents with themSea-floor spreading is the continually adding to the ocean floor
29Sea-floor Spreading Molten material rises up from the mantle It spreads out, cools off, & hardensIt pushes the older rock out on both sides of the ridgeNew crust forms!
31Wait a minute…!Hess’ idea of sea floor spreading caused scientists to revisit Wegener’s idea of continental drift!
32So where does all of the old crust being pushed out go? Subduction: It is the process by which the ocean floor sinks beneath a deep ocean trench & back into the mantle
33Sea Floor Spreading & Subduction… Can change the shape of the oceans!The ocean floor is renewed every 200 million years(That’s the time it takes for new crust to form, move across the ocean floor, & sink into a trench)
34What is the Theory of Plate Tectonics? 1965Tuzo Wilson proposed that the cracks in Earth’s surface were broken into section called “plates”He combined the idea of sea-floor spreading, Earth’s plates, &continental drift into a singletheory
35Plate Tectonics Theory A geological theory that states that pieces of Earth’s lithosphere are in constant, slow motion driven by convection currents in the mantle
36How does it work?Lithospheric plates float on top of the asthenosphereConvection currents rise in the asthenosphere & spread out under the platesNo plate can move without affecting another platePlates move extremely slow at 1-10cm per year
37As the plates move, collide, or pull apart…it produces GREAT changes on Earth’s surface
38Like volcanoes, earthquakes, mountain ranges, & deep sea trenches
393 types of plate boundaries: TransformDivergentConvergent
40TransformPlace where 2 plates slip past each other moving in opposite directionsEarthquakes often occur along these boundaries
41Divergent Place where 2 plates move apart Most occur at the mid-ocean ridgeSome occur on land creating a “rift valley” which is a deep valleyGreat Rift Valley in Africa is 3,000km long
42Convergent Place where 2 plates come together Collisions of 2 plates can cause:Oceanic to oceanicOceanic to continentalContinental to continentalWhen 2 plates collide the more dense plate comes out on top!
43Continental – Continental: mtns form Oceanic – Continental: Oceanic dives under the continentOceanic – Oceanic: the less dense of the 2 sinks into the trench
44What is an earthquake?Shaking & trembling that results from the movements of rock beneath Earth’s surfaceThe movement of Earth’s plates creates stress that squeezes/pulls the rock in the crust
45Stress A force that acts on rock to change its shape & volume 3 types of stressShearingTensionCompression
47ShearingStress that pushes a mass of rock in opposite directions
48TensionStress that pulls on the crust stretching the rock so it becomes thinner in the middle
49CompressionStress that squeezes rock until it folds or breaks
50What is a fault?A break in the crust where slabs of rock slip past each otherFaults usually occur along plate boundaries3 types:Strike-slipNormalReverse
51Strike-Slip FaultRocks on either side of the fault slip past each other sidewaysEx: San Andres Fault
52Normal Fault The fault is at an angle One block is above the fault & the other is below itEx: Rio Grande Rift Valley in New Mexico
53Reverse FaultSame structure as a normal fault, but the blocks move in opposite directionsEx: Appalachian Mts
54Where do earthquakes begin? Earthquakes occur in the lithosphere 100km below Earth’s surfaceThe focus is point beneath the surface where the rock broke causing the earthquakeThe epicenter is the point on the surface right above the focus
56Seismic WavesDuring an earthquake seismic waves race out from the focus in all directionsThe seismic waves are greatest at the epicenterSeismograph is the instrument used to record ground movement caused by seismic waves3 types:P wavesS wavesSurface waves
58P waves Primary Waves 1st to arrive Compress & expand the ground like an accordion
59S wavesSecondary Waves2nd to arriveVibrate the ground back & forth
60Surface Waves Come from P/S waves Move slowly Can cause the ground to roll like ocean waves
61How do they measure the size of the quake? Magnitude is the measurement of earthquake strength based on seismic waves & movement along faults3 ways to measure magnitude:Mercalli ScaleRichter ScaleMoment Magnitude Scale