Tectonic Plates

Crust

Thin + Cool; Divided into basaltic oceanic crust & continental

Mantle

Thick; Consists of hot rock rich in silicone and oxygen

Core

Scorching hot metal, mostly iron with nickel

Why was Earth molten when it was young?

Due to collisions with space debris

What elements were able to sink toward Earths center when planet fluid

Denser elements

How is earth layered?

According to density and composition

What is earth still doing?

Differentiating into chemically distinct layers/regions

Lithosphere

Cool + rigid layer; movement of these plates cause earthquakes, volcanic activity, and deformation of rock

Asthenosphere

Upper mantle and solid through plastic; plastic because of high temp and pressure, behaves like soft, elastic material

Lower mantle

Made up of solid rock, accounts for nearly half of earths mass

Seismology

Study of earthquakes and waves; energy radiates outward everywhere

Body waves

Travel through earths interior (P-waves and s-waves)

Surface waves

Travel on earths surface (Love waves and Rayleigh waves)

1906

Richard Oldham observed body waves travel together. S-waves stop, and p-waves refract; discovered core-mantle boundary

1909

Andrija Mohorovicic observed increase in seismic velocity; p-waves reach depth + discovered crust-mantle boundary

1936

Ingre Lehman observed p-waves refract at certain depths; discovered inner core

Continental drift evidence

Jigsaw fit of continents, fossil evidence, matching rock types, climate evidence

Continental drift mechanism

Deepest parts of the ocean are near continents and out in the middle of the ocean

Plate tectonics

Explain dramatic changing surface features of Earth

Speed (Features of plates)

Continental plates move slowly because they lack pull force; oceanic plates move faster because pull+suction forces combine to create a hole in subduction zones

Boundaries (features of plates)

Divergent = magma generation + lithosphere formation

Convergent = Magma generation + lithosphere destruction

Transform = No magma, no lithosphere

Divergent fault

Plates move away from eachother

Shallow earthquakes occur

Convergent fault

Plates move toward eachother, subduction under one another

Deep earthquakes occur

Subduction zone

oceanic-continental

Denser oceanic slab sinks into asthenosphere; generate magma

continental-continental

Continued subduction of crust brings 2 continents together

Less dense doesn’t subduction

oceanic-oceanic

2 oceanic plates converge; creates ocean trench

Volcanic islands form

Transform fault

Plates slide past each other, no new lithosphere created or destroy

Shallow but strong earthquakes

Mid-ocean ridge

Mid-Atlantic; slowly spreads 2-5cm per year and is center of Atlantic Ocean (rift valley)

East-Pacific summit with crack, spreads quickly 6-16cm per year (no rift valley)