Earths Crust Convection currents Continental drift – idea that continents have moved slowly to their current positions due to convection currents in.

Earth’s Crust

Convection currents

Continental drift – idea that continents have moved slowly to their current positions due to convection currents in the mantel.

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. http://geology.com/nsta/divergent-boundary-oceanic.gif

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

• 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.

http://www.allaboutspace.com/subjects/astronomy/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 – fault caused by tension stress that moves the hanging wall down relative to the foot wall.

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

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

Thrust Fault – is formed when compression causes the hanging wall to slide over the foot wall. (almost horizontal movement)

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

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

Rift Valley are valleys created when a block of land between two normal faults slide downward.

• End of chapter 10

Folds – are bends in rocks without breaking

• folds have two parts

1. Anticline – upward part of fold

2. syncline – downward part of fold

Anticline

Plateau – is a large area of flat land that is raised high above sea level. Usually bordered by cliffs or mountains.

Domes – is the uprising area caused by magma

Floating crust -

more dense less dense

•A balance exist between the downward force of the crust and the upward force of the mantle called ISOSTASY.