GL 107 Earth Systems Science

K. Hannula

Answers to discussion questions for 9/10/07

2.  Describe the motion that occurs at each type of plate boundary (divergent, convergent, and transform).

Divergent: plates move apart

Convergent: plates move toward one another

Transform: plates slide horizontally past one another.

3.  How are the crust, the mantle, and the core different from one another:

Crust: similar to granite or gabbro

Mantle: peridotite

Core: liquid or solid iron

Crust: more Si, K, Na, Ca

Mantle: more Fe, Mg than crust, but still a lot of Si so that most minerals are silicates

Core: mostly Fe (iron), some nickel, sulfur

Crust: outermost layer, extending to 5 to 70 km depth

Mantle: middle layer, extending from the base of the crust to a depth of about 2700 km

Core: innermost layer, filling the center of the earth

4.  How are continental and oceanic  crust different from one another:

Continental: thicker (20 to 70 km; average 35 km)

Oceanic: thinner (5 to 10 km; average 7 km)

Continental: approximately granite

Oceanic: gabbro

5.  How are lithosphere and asthenosphere different from one another:

Lithosphere: rigid

Asthenosphere: ductile, though mostly solid

Lithosphere: crust plus uppermost mantle; extends to a depth of about 100 km

Asthenosphere: found below the lithosphere

Lithosphere: forms the rigid tectonic plates

Asthenosphere: forms the soft, easily-deformed layer on which plates are able to move

6.  How are the lithosphere and asthenosphere related to the crust and the mantle?

The lithosphere includes all of the crust plus the uppermost part of the mantle.

The asthenosphere is entirely contained within the mantle.