How do geologic processes change the shape of Earth’s surface? What do Earth’s layers consist of? • Crust • Mantle • Core Crust • Layer of rock that forms Earth’s “outer skin” • Includes rocks, mountains, soil, water • Thin: 5-40km thick • 870◦C 2 Types: • Continental: Dry land (granite) • Oceanic: Ocean (basalt) Mantle • Layer of hot rock • 2,900km thick • 2,200◦C 2 Sub layers: • Lithosphere • Asthenosphere Lithosphere • • • • Rigid Much like the crust 100km thick Floats on top of the asthenosphere Asthenosphere • Plastic like • Material can flow slowly like hot tar • Has both solid & liquid qualities Core • Consists of iron & nickel • 5,000◦C • Makes up 1/3 of Earth’s mass 2 sub layers: • Outer Core • Inner Core Outer Core • Layer of molten material • Covers the inner core • 2,250km thick Inner Core • Dense solid ball of metal • Extreme pressure does not allow Fe & Ni to spread out to form liquid • 1,200km thick What are the 3 ways that heat is transferred? • Radiation • Conduction • Convection Radiation • Heat transferred by EM waves through space • EX: Sitting by the fire! Conduction • Heat transferred through direct contact • EX: Spoon in hot chocolate Convection • Heat transferred through a fluid movement of either a gas or liquid • EX: Chicken noodle soup heating on the stove! Which of these do you think happens in Earth’s mantle? • Convection! • Convection currents flow in the asthenosphere • Heated material rises to the top of the mantle (lithosphere), cools, then sinks back to the bottom What does the Theory of Continental Drift state? • 1910 • Alfred Wegener hypothesized that all the continents had once been a single landmass • A super continent called “Pangaea” Scientific Method • • • • • • Problem/Question Research Hypothesis Experiment Analyze Conclude Supporting Evidence of Wegener’s theory • Landforms • Fossils • Climate Landforms • South America & Africa have similar mountain ranges • Europe & North America have similar coal fields Fossils • Fossil-any trace of an ancient organism that has been preserved in rock • Mesoaurus fossils have been found in places now separated by oceans • Glossopteris (fern like plant) fossils have been in rocks in Africa, South America, Australia, India, & Antarctica Climate • Spitsbergen Island lies in the Arctic Ocean, north of Norway, covered with ice • Fossils of tropical plants have been discovered under the ice! • South Africa-deep scratches in rock indicate glacier movement there!!! REJECTED!!! • 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 Is sea-floor spreading like continental drift? • 1960 • Harry Hess, when studying the mid-ocean ridge, proposed that the ocean floor moved like a “conveyer belt” moving the continents with them • Sea-floor spreading is the continually adding to the ocean floor Sea-floor Spreading • Molten material rises up from the mantle • It spreads out, cools off, & hardens • It pushes the older rock out on both sides of the ridge • New crust forms! Wait a minute…! • Hess’ idea of sea floor spreading caused scientists to revisit Wegener’s idea of continental drift! So 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 Sea 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) What is the Theory of Plate Tectonics? • 1965 • Tuzo 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 single theory Plate 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 How does it work? • Lithospheric plates float on top of the asthenosphere • Convection currents rise in the asthenosphere & spread out under the plates • No plate can move without affecting another plate • Plates move extremely slow at 1-10cm per year • As the plates move, collide, or pull apart…it produces GREAT changes on Earth’s surface • Like volcanoes, earthquakes, mountain ranges, & deep sea trenches 3 types of plate boundaries: • Transform • Divergent • Convergent Transform • Place where 2 plates slip past each other moving in opposite directions • Earthquakes often occur along these boundaries Divergent • Place where 2 plates move apart • Most occur at the mid-ocean ridge • Some occur on land creating a “rift valley” which is a deep valley • Great Rift Valley in Africa is 3,000km long Convergent • Place where 2 plates come together • Collisions of 2 plates can cause: – Oceanic to oceanic – Oceanic to continental – Continental to continental • When 2 plates collide the more dense plate comes out on top! • Continental – Continental: mtns form • Oceanic – Continental: Oceanic dives under the continent • Oceanic – Oceanic: the less dense of the 2 sinks into the trench What is an earthquake? • Shaking & trembling that results from the movements of rock beneath Earth’s surface • The movement of Earth’s plates creates stress that squeezes/pulls the rock in the crust Stress • A force that acts on rock to change its shape & volume • 3 types of stress – Shearing – Tension – Compression Shearing • Stress that pushes a mass of rock in opposite directions Tension • Stress that pulls on the crust stretching the rock so it becomes thinner in the middle Compression • Stress that squeezes rock until it folds or breaks What is a fault? • A break in the crust where slabs of rock slip past each other • Faults usually occur along plate boundaries • 3 types: – Strike-slip – Normal – Reverse Strike-Slip Fault • Rocks on either side of the fault slip past each other sideways • Ex: San Andres Fault Normal Fault • The fault is at an angle • One block is above the fault & the other is below it • Ex: Rio Grande Rift Valley in New Mexico Reverse Fault • Same structure as a normal fault, but the blocks move in opposite directions • Ex: Appalachian Mts Where do earthquakes begin? • Earthquakes occur in the lithosphere 100km below Earth’s surface • The focus is point beneath the surface where the rock broke causing the earthquake • The epicenter is the point on the surface right above the focus Seismic Waves • During an earthquake seismic waves race out from the focus in all directions • The seismic waves are greatest at the epicenter • Seismograph is the instrument used to record ground movement caused by seismic waves • 3 types: – P waves – S waves – Surface waves P waves • Primary Waves • 1st to arrive • Compress & expand the ground like an accordion S waves • Secondary Waves • 2nd to arrive • Vibrate the ground back & forth Surface Waves • Come from P/S waves • Move slowly • Can cause the ground to roll like ocean waves How do they measure the size of the quake? • Magnitude is the measurement of earthquake strength based on seismic waves & movement along faults • 3 ways to measure magnitude: – Mercalli Scale – Richter Scale – Moment Magnitude Scale Mercalli Scale • Measures the intensity • Not precise Richter Scale • Rates the size of seismic waves using a particular seismograph • Accurate measurements for nearby earthquakes Moment Magnitude Scale • Rates the total energy released by an earthquake near or far What types of damage can a quake cause? • • • • • • Damage/destroy buildings Topple power lines Break water & gas lines Cause landslides Can cause aftershocks days/months later Can cause tsunamis Tsunamis • Large wave that occurs when an earthquake displaces water in the ocean What causes volcanoes? • A volcano is a weak spot in Earth’s crust where magma comes to the surface • They form at: – Divergent boundaries – Convergent boundaries – Hot spots Divergent Boundaries • Most volcanoes occur here Ex: Mid-ocean ridge •Volcanic belts occur along plate boundaries where lithospheric plates are weak Ex: Ring of Fire Ring of Fire • Major volcanic belt formed by volcanoes that rim the Pacific Ocean Convergent Boundaries •Island Arc-when 2 oceanic plates collide creating an arc of islands Ex: Japan, New Zealand, Caribbean Islands Hot Spots • Where magma rises up from the mantle melting Earth’s crust • Often occur in the middle of a plate Ex: Hawaiian Islands, Yellowstone National Park How do volcanoes erupt? • Magma is under extreme pressure in the mantle • It bubbles up through cracks in Earth’s crust • Pressure decreases as magma nears Earth’s surface • Lava bubbles out of the volcano What does the inside of a volcano look like? Magma Chamber • Where magma is stored under the volcano Pipe • Magma moves through this long pipe that connects the magma chamber to Earth’s surface Vent • Opening where gas and lava leave the volcano Crater • Hollowed-out area at the top of a volcano Volcanic Neck • Magma that hardens inside the pipe Dike • Magma that forces itself “across” rock Sill • Magma that squeezes between layers of rock Batholith • A mass of rock formed when a large body of magma cools inside the crust What are the different types of volcanoes? • Shield Cone • Cinder Cone • Composite Shield Cone Volcano Cinder Cone Volcano Composite Volcano Volcanoes in the US Mt. Hood Mt. St Helens Mt. Kilauea What are the stages a volcano goes through? • Active→Dormant→Extinct Active • It’s alive! • It is erupting or shows signs of erupting Dormant • It’s sleeping… • It is expected to become active in the near future Extinct • Dead as a door nail. • Unlikely to erupt again The End!!! Sike…this is the end!