GS 3310 Chapter 5

What lines of evidence were used to support the continental drift hypothesis?

Wegener observed the similarity between coastlines that were on opposite sides of the Atlantic Ocean which was when he suggested that there once was a giant land mass but due to wave erosion and time the land mass (Pangea) was eventually broken up and "drifted away" into smaller pieces. Another form of evidence was the discovery of similar fossils in different lands which supported Wegener's hypothesis for Pangea.

What was Pangea?

Wegener's "supercontinent" that consisted of all of Earth's landmasses.

In what major way does the plate tectonics theory depart from the continental drift hypothesis?

A major departure of the plate tectonics theory is that large plates contain both continental and ocean crust and the entire plate moves. In continental drift, it is proposed that the sturdier continents "drifted" by breaking through the oceanic crust like how ice breakers cut through the ice.

How does the continental drift hypothesis account for the apparent wandering of the Earth's magnetic poles?

It accounted for the wandering of magnetic poles because if the magnetic poles remained stationary then their apparent movement is produced by continental drift.

What are the three major types of plate boundaries? Describe the relative plate motion at each one of these boundaries.

Divergent boundaries: when two plates move apart which causes hot material from mantle to rise and create a new seafloor. Convergent boundaries: when two plates move together which creates a mountain system. Transform fault boundaries: when two plates grind against each other without the production or destruction of the lithosphere

What are the three types of plate boundaries?

Divergent, convergent, and transform fault.

Who is credited with developing the continental drift hypothesis?

German meteorologist Alfred Wegener.

Early in this century, what was the prevailing view of how land animals migrated across the vast expanses of ocean?

Opponents of continental drift claimed that due to transoceanic land bridges animals were able to make their way across the oceans.

Define the term paleomagnetism.

Paleomagnetism is the natural remnant magnetism in rock bodies. The permanent magnetization acquired by rock that can be used to determine the location of the magnetic poles and the latitude of the rock at the time becomes magnetized.

On what basis were plate boundaries first established?

Plate boundaries were first established on the basis of plotting the locations of earthquakes and volcanoes.

What is the theory of plate tectonics?

Proposes that Earth's outer shell consists of individual plates that interact in various ways and thereby produce earthquakes, volcanoes, mountains, and the crust itself.

What is seafloor spreading?

Seafloor spreading is the process of producing a new seafloor between two diverging planes.

Briefly describe how the Himalaya Mountains formed.

The Himalayas were formed when India "rammed" into Asia, during this collision the continental crust buckled and fractured as well as generally shortened and thickened.

List the evidence that Wegener and his supporters gathered to substantiate the continental drift hypothesis.

The continental jigsaw puzzle, fossils, rock types and geological features, and ancient climate.

Explain why the discovery of the fossil remains of mesosaurus in both South American and Africa, but nowhere else, supports the continental drift hypothesis.

The discovery supported continental drift because according to Wegener, if the mesosaurus was able to travel longer distances across the South Atlantic then its remains/fossils would have been more widely distributed but since this didn't happen South America and Africa must have at one point been connected.

What is the evidence used to support the plate tectonics theory?

The evidence used to support is the ages and thickness of sediments from the floors of deep ocean basins and the existence of island chains that formed over hot spots and provide a frame of reference for tracing the direction of plate motion.

What was one of the main objections to the continental drift hypothesis?

The main objection to Wegener's hypothesis was from his inability to identify a credible mechanism for continental drift. Physicist Harold Jefferys pointed out that Wegener's proposition of gravitational forces was wrong and that instead of breaking up the land it would have brought Earth's rotation to a halt in a matter of years.

What models have been proposed to explain the driving mechanism for plate motion?

The slab pull and ridge push.

What is the subduction zone? With what type of plate boundary is it associated?

The subduction zone is a long narrow zone where one lithospheric plate descends beneath another. This is associated with convergent boundaries.

Differentiate between transform faults and the other two types of plate boundaries.

Transform fault boundaries: plates slide horizontally past one another without the production or destruction of lithosphere.