Plate Tectonics

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-Provides the mechanisms for the next segment of class - Earthquakes - Volcanoes

- Earth is a dynamic system not only as climate, but in solids as well - Rock solids move and interact - Source of energy is from within the Earth - Residual heat from Earths formation - Very term and concept heavy. Get these things down

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Components of Earth

Crust (two types)-

Oceanic Crust- Thin, dense crust formed at mid-ocean ridges (basaltic). Continental Crust- Thick, less dense continental material (silicic). Mantle- Solid but acts plastic (moves over geologic time) Outer Core- Liquid iron and nickel Inner Core- Solid iron and nickel

Components of Earth

Lithosphere- Consists of crust and upper part of upper mantle

Asthenosphere- Consists of highly viscous portion of the upper mantle

These terms are described by their mechanical qualities, not chemical/mineral!

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- Crust is broken into pieces - Called Tectonic Plates - These plates move atop the mantle due to underlying forces (and others). We call this process-

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Plate Tectonics- The big picture that describes movement of crustal plates.

Driving forces

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Convection drives plate tectonics. Tectonic plates in turn move on atop the currents and interact with each other

- Smashing into each other - Pulling away from each other - Rubbing against each other

Boundaries

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3 types

Divergent- Where plates pull apart Convergent- Where plates smash together Transform- Where plates pass one another

Boundaries

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Divergent Boundary- Rising magma creates pull apart conditions and crust rips apart. New crust forms at boundary.

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Boundaries

Divergence of rock (think of this as stretching) can occur on a continent. Leads to a thinning of the continent and Basin and Range (Nevada)

Nevada is Americas stretch mark

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Boundaries

Convergent Boundary- Two plates smash into each other. These are subduction zones and collision zones (mountain building areas).

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Boundaries

Hand sample rock densities- - Oceanic Crust (basalt) is dense (heavy) - Continental crust (silica) is less dense (light) When the two encounter one another, the dense material subducts under the lighter material.

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Boundaries

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Boundaries

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Boundaries

Transform Boundary- Plates moving in opposite direction slide past one another.

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Boundaries

The San Andreas fault is a transform boundary between the Pacific and North American plates Cal Poly Pomona is moving North in reference to Victorville

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Evidence

- Many theories have been presented to explain the concept of the continents moving.

- 1912- Alex Wegener proposed that all continents were once part of a supercontinent he called Pangaea. Hypothesized the continents moved and called it Continental Drift.

- Not widely accepted until the 1960s

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Evidence

Many lines of evidence, from the obvious to quite technical. We will focus on three. 1) Continental fit 2) Regional similarities 3) Sea floor age

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-Next time-

Exercise #1 (from the manual) & Tectonic Regions