Exam 3: Plate Tectonics

The magnetic dip preserved in a rock indicates

Rifting occurs at oceanic spreading ridges,but not within continents,because continents are so thick and strong.

With increasing distance from an oceanic ridge,

The Appalachian Mountains of eastern North America were formed by continent-continent collision.Today,these mountains are still being uplifted by the same type of collision

Hot spots

The strength of a rock

The asthenosphere is a weak,locally partly molten layer over which lithospheric plates can move.

A ductile material is one that

The earth's polarity has remained the same since its existence.

Transform faults that offset segments of a spreading ridge are formed because rates of spreading are not constant along any one rift zone so shearing develops when one segment grows faster than another.

Rocks may behave differently over the long spans of geologic time than they do in short-term laboratory experiments.

The San Andreas fault is a good example of a

The best explanation for the distribution of Glossopteris and Mesosaurus is that they lived when continents on which their fossils are now found were once connected then later were rifted and drifted apart.

Example of the movement of the following plates: continent-ocean; continent-continent; ocean-ocean is best referred to as the

Divergent plate boundaries

Because the sea floor is protected from weathering,seafloor rocks are better preserved and generally older than continental rocks.

The idea of continental drift was not proposed until the 1960s,when the first evidence to support it was discovered.

A possible "driving force" for plate motions is

Seawater interacting with hot sea floor at spreading ridges may produce mineral deposits.

Continental drift may explain evidence of past glaciation in regions now located in the tropics,because local climate is strongly controlled by latitude.