What role does the seafloor play in the growth of the continents How does the an

Question

What role does the seafloor play in the growth of the continents How does the angle of subduction affect the evolution of the overlying plate? How does the sediment on the seafloor affect the geologic evolution of the margin? How does the nature of the overlying plate affect the nature of the landform How do we get ophilites? What kind of faults and folds would we expect to form: Near a mid ocean ridge? Near an accretionary wedge? Near a back arc spreading zone? On the continental shelf / slope? What are some of the ways sediment gets from the land mass to the deepest seafloor?

Explanation / Answer

1. We have two types of subduction angles . 1. Flat dip subduction 2. Steep dip subductionThe slab dip is related to the stress in the overriding plate.A steep dip means Extension in the back arc. A shallowp dip means compression in the back arc.

2. Sediment on the seafloor originates from a variety of sources, the terms "terrigenous" to describe those sediments derived from eroded material on land, "biogenic" for those derived from biological matter, "volcanogenic" for those that include significant amounts of ash, "hydrogenous" for those that precipitate directly from sea water, and "cosmogenic" for those that come from interstellar space.The different combinations of each process' effectiveness result in a commensurate variety of sedimentation rates. Sediment can accumulate as slowly as 0.1 millimeter (0.04 inch) per 1,000 years (in the middle of the ocean where only wind-blown material is deposited) to as fast as 1 meter (3.25 feet) per year along continental margins . More typical deep-sea rates are on the order of several centimeters per 1,000 years.

3.An ophiolite is a section of oceanic crust and upper mantle (oceanic lithosphere) that has been transported along thrust faults and uplifted and emplaced on the margins of a continent or other land mass. The emplacement of ophiolites occurs during mountain-building events which are accompanied by the closure of an ocean basin. The process of emplacement of an ophiolites on the margin of a continent along a thrust fault is called obduction.

4. Mid ocean ridge - Normal faults

Accretionary wedge- Thrust fault

spreading zone- Strike-slip fault

Continental shelf/slope- Normal fault

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