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

http://en.wikipedia.org/wiki/Image:Bay_Bridge_collapse.jpeg

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!