Plate Tectonics

What is the theory of plate tectonics?

• The theory that the earth's crust is broken up into plates

• The theory that the earth's crust is made of 13 major plates

• The theory that the earth's crust is constantly moving

• The theory that the earth's crust is made of semirigid plates

What are the three types of plate boundaries?

• Midocean ridges, deep-sea trenches, and transform faults

• Continental drift, subduction zones, and strike-slip faults

• Volcanic arcs, subduction zones, and transform faults

• Midocean ridges, deep-sea trenches, and volcanic arcs

What did James Hall observe about sediments in mountain belts?

• They are at least ten times thicker than those in continental interiors

• They are made of ancient and folded geosynclines

• They are hardened and consolidated into plates

• They are found in the Indian Ocean

What did Alfred Wegener propose in the early 20th century?

• Continental plates rupture, drift apart, and collide with each other

• The earth's crust consists of sima and sial materials

• Continental margins have different types: Atlantic and Pacific

• The earth's crust is constantly moving due to thermal convection currents

What did the study of seafloors in the 1920s reveal?

• The rocks on one side of the midocean ridge produce a mirror-image geomagnetic pattern

• The age of basaltic crustal rocks on the seafloor

• The presence of marine sediment at the ridge crest

• The existence of fracture zones along the midocean ridge

What effect does the melting of subducted ocean crust have?

• It produces new magma that rises to the earth's surface

• It causes earthquakes at shallow depths near volcanic island arcs

• It creates long chains of volcanic islands

• It forms ore deposits of valuable metallic minerals

Who demonstrated the global continuity of subduction zones?

• J. Tuzo Wilson

• Harry Hammond Hess

• Xavier LePichon

• Robert Sinclair Dietz

What did Xavier LePichon work out from seismic evidence?

• The geometry of the plates

• The positions of the continents and oceanic plates

• The formation of Pangaea

• The process of subduction

What did Robert Sinclair Dietz reconstruct based on Wegener's evidence?

• The positions of the continents and oceanic plates

• The formation of Pangaea

• The existence of Rodinia

• The process of subduction

What is the theory of plate tectonics still debated and tested?

• Because it is a paradigm and a center of controversy for the geological sciences

• Because it is based on seismic evidence

• Because it explains the structure, history, and dynamics of the earth's crust

• Because it is supported by the study of seafloors and subduction zones