April18th, 2008

April18th, 2008April18th, 2008• BellRinger

– Examples 1, 2, 3 pgs 95-97 in PSAE Coach book

• Objectives– Describe the structure of Earth– Explain how Earths dynamic processes create a

changing landscape

• Homework– What type of evidence was necessary to prove that

Pangea existed?

April 21April 21stst, 2008, 2008

• BellRinger– Complete questions on pg 102, 103, & 105

• Objectives– Explain how Earths dynamic processes create

a changing landscape

• Homework– Complete MC questions. This will be graded!!

Chapter 28Chapter 28

THE CHANGING EARTHTHE CHANGING EARTH

The Layers of EarthThe Layers of Earth

The Layers of EarthThe Layers of Earth

1. Crust- a thin surface covering the Earth.– 2 kinds: Oceanic & Continental– What is a crack in the crust called??

2. Mantle- a thick molten layer between the core and the crust

3. Outer Core- molten iron, nickel, and oxygen

4. Inner Core- solid iron and nickel– The core’s temperature ranges between

2,000 oC and 5,000 oC…hot, hot, hot!

Rock Cycle pg 103Rock Cycle pg 103

Igneous RocksIgneous Rocks

• Form at the surface from lava and inside the crust from magma that has cooled

• Rocks that cool slowly are rougher in texture

• Rocks that cool fast have smoother textures

Igneous RockIgneous Rock

BasaltBasalt

GraniteGranite

Sedimentary RocksSedimentary Rocks

• From as a result of weathering and erosion

• Formed by processes mainly at the Earth’s surface

Metamorphic RocksMetamorphic Rocks

• Form under conditions of extreme pressure and temperature

• Any type of rock can change to metamorphic under these conditions

The Surface of EarthThe Surface of Earth

• Is there a pattern??? • YES!!!

Continental DriftContinental Drift• The idea that the continents were once

one landmass; a “super-continent” named Pangea

• How is this possible?

mantle convectionmantle convection

Heat transferred from the core to the mantle produces a slow convection

of the material in the mantle

•Thermal Convection Demo

Sea Floor SpreadingSea Floor Spreading

• Mid-Ocean Ridges: mountain ranges on the ocean floor

• The closer you get to a ridge, the younger the ocean floor.

• Scientists concluded that the “new” land must be coming up through the ocean ridges

The The Theory Of Plate Theory Of Plate TectonicsTectonics

• Explanation of how continents move• Earth's outer layer is made up of

tectonic plates, which are moving– explains the how and why behind

mountains, volcanoes, and earthquakes

• What is the area called where 2 plates meet?

Plate BoundariesPlate Boundaries

DivergentDivergent Plate Boundaries Plate Boundaries• Plates are moving

apart, allowing molten material to rise up and create new crust– Mid-ocean ridges– Sites of

earthquakes and volcanoes

ConvergentConvergent Plate Plate BoundariesBoundaries

• Occurs when two plates approach each other– Subduction: one

plate slides under another

• Often the site of volcanoes

– Collision can also occur between approaching plates

• Mountains form

Convergent PlatesConvergent Plates

• Subduction:

• Collision:

TransformTransform Plate Boundaries Plate Boundaries

• Occurs when 2 plates slide past each other

• No crust is created or destroyed– Earthquakes

• What “famous” transform plate boundary is located in the US?

Review of BoundariesReview of Boundaries

Facts & Figures: EarthquakesFacts & Figures: Earthquakes

• Largest EQ recorded in the US: 9.2• Largest in world: 9.5• 500,000 detectable EQ’s each year. • More damage is caused indirectly from the EQ, not the

EQ itself.• 10,000 EQ’s will develop in southern California this year.

However, most will not be felt• Powerful EQ’s rocked the Midwest in the 1800’s. One

recorded a magnitude of over 8 and caused church bells to ring in Boston Massachusetts

• Deadliest EQ: China in 1557, killing 830,000 people

EarthquakesEarthquakes• Defn: Vibrations of the earth’s crust from

the movement of plates along faults– As plates move, they stretch/compress, and

stress builds up– When the rocks break or change shape, they

release stored energy in the form of movement

– LIKE A RUBBER BAND!

– This creates seismic waves that move through Earth

EarthquakesEarthquakes

Seismic WavesSeismic Waves

• Body Waves– originate from the

center of an EQ– 2 kinds:

• P waves & S Waves

• Surface Waves– Move along the surface of the Earth

Measuring EarthquakesMeasuring Earthquakes

• Richter scale:– Related to the amplitude of the seismic waves– More accurate for earthquakes that are near

• Mercalli scale: – Uses 12 descriptive categories that describe

the damage caused by earthquakes

Where do Earthquakes Occur?Where do Earthquakes Occur?

• Along plate boundaries, faults

Earthquakes in the US:Earthquakes in the US:

SAN ANDREAS FAULTSAN ANDREAS FAULT

• A well known transform boundary where the Pacific plate and North American plate meet

• Average rate of motion across the San Andreas Fault is 2 in./yr. (3 million years L.A. will be next to S.F.)

Earthquakes in the US:Earthquakes in the US:

OTHER FAULT LINESOTHER FAULT LINES• Do EQ’s occur anywhere else in the US?• YES!...it’s been a while, but there are other fault

lines in the US.• New Madrid fault in Midwest

– 250 miles long– Last major EQ in 1895

• Eastern US– Last major EQ in 1886

• Why would an EQ be so damaging in these areas today?

Where do Volcanoes Occur?Where do Volcanoes Occur?Most volcanic activity is

associated with plate boundaries.

Where do Volcanoes Occur?Where do Volcanoes Occur?Most Volcanoes occur

within the Ring of Fire!

Additional Sites of VolcanoesAdditional Sites of Volcanoes

• Subducting plates beneath the ocean floor can create an island arc.

• This is how the Hawaiian Islands were formed.

Mount VesuviusMount Vesuvius

Mount St. HelensMount St. Helens