Plate Tectonics Learning Goal: Comprehend plate tectonics and apply in lab.

Convection currents

Continental drift – idea that continents have moved slowly to their current positions due to convection currents in the mantle. Pangea – the idea that the all land masses on earth were once a single large land mass.

Ocean floor spreading – theory that hot less dense material below Earth’s crust rises toward the surface at the mid-ocean ridges. Then, it flows sideways, carrying the seafloor away from the ridge in both directions. Convection current – unequal distribution of heat in the mantel causes a net movement in a circular motion.

The Earth’s CRUST is the outer most part of the Earth’s surface. Average 32 km thick (19.84 miles) Thickest point 70 km (in mountains) Thinnest point 8 km (under ocean)

Plate tectonic – theory that Earth’s crust and part of the upper mantle are broken into sections called plates. Lithosphere – all of the earth’s crust and part of the upper mantle. y/planets/earth/Inside.shtml Asthenosphere – plastic like layer below the lithosphere. The ridged plates of the lithosphere “float” on the more plastic layer called the asthenosphere.

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Deformation – The breaking, tilting, and folding of crustal rock due to crustal movement. (three types of forces) 1.Compression – squeezing of earth’s crust that compacts the rock. Convergent boundary 2. Tension – is the pulling apart of the earth’s crust. Divergent boundary. 3. Shearing – pushes rocks side by side in opposite directions. Transform boundary.

Convergent boundary Divergent boundary Transformation boundary

subduction Rift valley

FAULTS Normal Fault (Divergent Boundary) – fault caused by tension stress that moves the hanging wall down relative to the foot wall.

Fault block mountain is a mountain created by blocks of rock uplifted by normal faults.

Divergent boundary in Iceland

Reverse Fault (Convergent Boundary) – fault caused by compression forces where the hanging wall will move up relative to the foot wall.

In Lateral (strike-slip) faulting (Transform Boundary), the two blocks move either to the left or to the right relative to one another. Strike-slip faults are associated with crustal shear.

San Andreas Fault, CA

Facts about folds/faults. 1.increased temp. =‘s fold 2.decreased temp =‘s fault 3.increased pressure =‘s fold 4.decreased pressure =‘s fault 5.rock type – brittle =‘s fault 6.rock type – ductile =‘s fold 7.time – greater the time =‘s fold 8.time – less time =‘s fault

Earthquakes Earthquake – is the shaking and trembling that results from the sudden movement of part of the Earth’s crust. Tsunamis – A giant sea wave produced by an earthquake.

Seismic Waves Focus – The point beneath the Earth’s surface where the rocks break and move, the underground origin of the earthquake. Epicenter – The point directly above the focus, on the earth’s surface where the origin of an earthquake is above ground.

Faults- Once the elastic limit of rocks is passed, they break and move along surfaces. 3 types of faults are: Normal Fault- These form at divergent boundaries. Reverse Fault- These form at convergent boundaries. Strike-Slip Fault- These form at transform boundaries.

Seismic waves – earthquake waves. *Three types. 1. Primary waves (P-waves) - arrive at a given point before any other type of seismic wave. Will pass through solid, liquid and gas.(fastest of the three) 2. Secondary Waves (S-waves) – arrive at a given point after the P wave. (second fastest) Will only travel thru solids. Will NOT pass through liquids and gases thus creating a shadow zone.

3. Surface waves (L-waves) – slowest moving seismic waves. Arrives last.

Volcanoes Volcano –A mountain that forms when layers of lava and volcanic ash erupt and build up. Magma – rock that exists as a hot liquid deep within the earth. Lava – is magma that reaches the Earth’s surface.

Composite Volcanoes –Violent eruptions due to high amount of silica (D.A.N, quartz, mica, feldspar) which is light in color and is explosive because of large amounts of gas, ash and lava.

Domes – is the uprising area caused by magma

Shield volcano – Volcanoes composed of quiet lava flows. The lava has a low amount of silicia (D.A.N, quartz, mica feldspar) and is dark in color. These volcanoes are nice with gently sloping sides with very wide base.