GL 107 Earth Systems Science

K. Hannula

Discussion questions for 11/5/07

1.  Define:

• Continental margin:  the boundary between a continent and an ocean

• Abyssal plain:  the deep, fairly flat area that forms the bottom of most of the area covered by oceans

• Mid-ocean ridge: an area of higher elevation within ocean basins that marks the location of a divergent plate boundary.

2.  Compare and contrast passive and active continental margins.

Passive continental margin:

• found within a tectonic plate, not on a plate boundary

• the edge of a continent that rifted apart long ago

• usually little topography on the continent

• no earthquakes or volcanoes

Active continental margin:

• continental margin at an ocean-continent convergent plate boundary (a subduction zone)

• continent is usually mountainous near margin

• earthquakes and volcanoes are common

• deep-sea trench is located near the margin; continental shelf is very narrow

3.  Describe the parts of a passive continental margin.

• continental shelf: shallow water nearest continent, underlain by continental crust.  Parts of continental shelves are above sea level when sea level is low.

• continental slope: steeper area at the oceanward edge of the continental shelf

• continental rise: area of gradually increasing water depth between the continental slope and the abyssal plain.  Sediment derived from the continental slope is deposited on the continental rise on deep sea fans.