GEO 1405 Chapter 2 Quiz

What is the relationship between the crust and the lithosphere?

All of the crust is contained within a larger layer called the lithosphere.

What is the relationship between the mantle and the asthenosphere?

All of the asthenosphere is contained within a larger layer called the mantle.

As oceanic crust is subducted, it melts, forming a body of magma. When this magma rises and interacts with the overlying continental crust, what change occurs in the composition of the magma?

The silica content of the magma increases. As the mafic magma rises and the overlying continental crust melts and mixes with the magma, the silica content of the magma increases, causing it to become intermediate, or even felsic in composition.

Late Paleozoic sedimentary rocks often contain extensive coal seams that were used to support the existence of Pangaea. What would the climate have been at that time and at the location where the coal deposits were formed, and what would it indicate about the continent's past latitude?

Warm, humid climate near the Equator Swamp vegetation needs a lot of moisture and plenty of warm temperatures to thrive. The conditions would have been (and are today) present near the Equator.

What surface feature would you expect to form if both a hot spot and a tectonic plate are stationary?

a single volcano

Do fracture zones near transform boundaries play a role in plate motion?

No, fracture zones play no role in plate motion.

What evidence supports that the glaciers on the southern continents were once part of a single, massive ice sheet?

Striations Striations are scratches or grooves created by glacial debris as it moves. The striations found on the southern continents all radiate from the center of the south part of Pangaea.

At a convergent boundary, what is the relative motion of plates on each side of the boundary?

The plates move toward each other. At convergent plate boundaries, the plates move toward the boundary.

Transform boundaries are classified under which type of fault?

strike-slip

Earth's lithospheric plates are composed of crust and which of the following layers?

the outermost portion of the mantle Earth's lithosphere consists of the crust and the outermost portion of the mantle.

What surface feature provides evidence for the location of hot spots?

volcanoes within tectonic plates

When will a hot spot volcano become extinct?

when the volcano is carried away from the hot spot by the tectonic plate

How was the fossil record of ancient life used to support Wegener's hypothesis about Pangaea?

Fossils of identical organisms were found on several continents, indicating the continents were once joined. When organisms are separated into two smaller groups by a physical barrier (i.e., the Atlantic Ocean), then they follow different evolutionary paths. The organisms Wegener cited were identical on both continents.

When matching up once-joined continents such as South America and Africa, the coastlines do not fit together as nicely as the continental shelves. Why might this be the case?

The continental shelves are the edges of the continent. The shoreline simply shows where the sea level is in relation to topography. Depending on sea level, continental shelves are often underwater and below the erosive effects of wave action.

Which of the following processes can be observed at the margins of lithospheric plates?

faulting, earthquakes, volcanoes, mountain building At the margins of lithospheric plates, earthquakes, faults, volcanoes, and mountains occur where the plate edges interact.

As oceanic crust is subducted below continental crust, which of the following factors most directly drives the melting that will fuel volcanoes at the surface?

water Water is the factor that lowers the melting point of mafic minerals in the plate being subducted, frequently causing volcanism at the surface.

When oceanic and continental crust collide at a subduction zone, one plate is forced under the other. The angle at which the subducting plate descends is due to which of the following factors?

1.the age of the plate being subducted. 2. the density of the plate being subducted. Older crust subducts at a steeper angle because something about the plate changes over time. Density is the primary factor controlling sudbuction angle.

A continental volcanic arc is formed when which of the following conditions exists?

A piece of oceanic crust is subducted below continental crust. A continental volcanic arc forms when oceanic crust is subducted under continental crust and a line of volcanoes forms on the continent as a result.

Although new crust is being formed at divergent boundaries, Earth remains the same size. Which of the following statements provides the best reason for this?

An equal volume of crust is being consumed at convergent boundaries As new crust is being created at divergent plate boundaries, if an equal amount were not consumed at convergent plate boundaries, Earth would increase in size.

Which of the following statements best describes Wegener's idea of continental drift?

Continents were formerly in different positions on the Earth and have shifted to their present locations over time. Wegener believed that the continents had once been part of a supercontinent that he named Pangaea.

Which tectonic boundary results when two tectonic plates pull apart from each other?

Divergent boundaries Divergent boundaries form because of tensional stress.

In studies of rock obtained from ocean basins all over Earth, the oldest ages obtained are approximately 200 million years before the present. Why have no older oceanic rocks been discovered?

Due to tectonic activity, rocks on the ocean floor are continually recycled. As the lithospheric plates move around, ocean floor is constantly being consumed.

Crustal rifting is currently occurring in East Africa. Which of the following features would you expect to find there?

Normal Faults; Long, wide valley; Lava flows

What is the relationship between the mantle and the lithosphere?

Some of the mantle is contained within a smaller layer called the lithosphere.

When oceanic crust is subducted beneath continental crust, partial melting can occur. Which of the following best explains why the resultant magma rises through the crust toward the surface?

The magma is less dense than the surrounding solid rock. Liquid rock is less dense than solid rock. If the density differential is sufficiently large, it rises toward the surface.

The formation of the Himalaya and the Tibetan Plateau was caused by which of the following events?

There was a collision of two pieces of continental crust at a subduction zone. The Himalaya and the Tibetan Plateau were created by the collision of two lithospheric slabs bearing continental crust. Since continental crust cannot subduct, the continental crust riding on both plates (along with some of the intervening oceanic crust) were thrust upward, creating a towering mountain chain.

What role do transform boundaries play?

Transform boundaries connect other segments of plate boundaries.

What is the relationship between transform boundaries and mid-ocean ridges?

Transform boundaries connect segments of mid-ocean ridges.

Divergent boundaries are not one, smooth ridge of separation. Instead, they are broken into a series of segments, with different segments of fault offset from others. What features allow for the offset of divergent boundaries?

Transform faults Transform faults account for the lateral offset that is seen along divergent boundaries.

Currently the Juan de Fuca plate is interacting with the North American plate where inland volcanoes and deep focus earthquakes are occurring. What type of plate boundary is this?

a convergent plate boundary The boundary that exists between the Juan de Fuca plate and the North American plate is a convergent plate boundary.

Which of the following lithospheric plates is not included among the seven largest?

the Philippine plate The Philippine plate is one of the intermediate-sized lithospheric plates.