Earth’s Interior Earth System Science – Foster I.

Earth’s Interior
Earth System Science – Foster
Plate Tectonics
a. Theory of continental drifti. The earth is a dynamic planet with the continents in constant motion
b. Continents once joined together forming a supercontinent called Pangea
(formulated by Alfred Wegener) meaning all land
i. Supported with
1. geologic (rock)
2. biologic (life)
3. climatological (past weather)
4. Fits together along the continental shelves very well
a. Seismic Waves- earthquake-generated waves traveling through the earth’s interior
i. give us clues to the composition of the earth
Types of Waves
a. p-waves- (primary waves)
i. compress and expand rock
ii. are the fastest of all seismic waves
iii. First waves to register on seismograph
b. s-waves- (secondary waves)
i. vibrate up and down
ii. 2nd to register on a seismograph
Measuring Earthquakes
a. Seismograph- Device which measures seismic waves
Plate Movement
a. Transform-fault boundary- plates are sliding past one another
Ex. San Andreas fault in California
i. caused by sheering forces
b. Divergent Boundaries- two plates are moving apart
i. Creates rift valleys – large spreading valleys
ii. Sea floor spreading- a rift valley on sea floor
1. Observable reverse polarization
a. Alternating bands of rock
iii. Caused by tensional forces
c. Convergent Boundaries- two plates move towards each other
i. Leads to subduction- one plate (usually oceanic crust) goes beneath the other
(continental crust).
ii. Caused by compressional forces
Ex. Andes Mountains in S. America (Still growing b/c of subduction)
iii. Common place to find volcanoes
Ex. Cascade Range (Mt. St. Helens, Mt. Rainier…)
Layers of the Earth
a. The corei. Composed mostly of iron and nickel
ii. Inner Core- very hot but still solid due to high pressure of the earth
iii. Outer Core- less pressure from the earth so iron and nickel are liquid
-Flow in the outer core generates an electric current that powers the earth’s magnetic field
b. The mantle- rocky layer that is about 3000km thick.
i. Two sections
1. Lower mantle
2. Upper mantle-two sections
a. Asthenosphere- behaves in a semifluid manner
b. Lithosphere- rigid and brittle
c. The crust- uppermost portion of the lithosphere
i. ~10 km thick – oceanic crust- below ocean
ii. ~20 - 60 km thick- continental crust – below land