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!