earth science HW 8

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.

Which statement best explains the formation of seamounts?

They represent volcanoes situated over mantle plumes that have since moved away from their source of magma and subsided.

Which feature would you expect to find associated with continental collisions?

reverse faults

Which feature would you expect to find at the mouth of a submarine canyon? alluvial fan a deep sea fan beach delta talus slope

a deep sea fan

Where are most modern divergent plate boundaries found?

at mid-ocean ridges

What is mass movement?

movement of material under the influence of gravity alone

Which type of faulting is associated with the development of new ocean floor?

normal faulting

Which coast represents an active continental margin?

the west coast of South America

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

Where do most divergent boundaries originate?

within continents

How are slumps and slides related?

Slumps are a type of slide in the special case where the rupture surface is curved.

Moving off the east coast of North America, identify the sequence of environments you would encounter as you move deeper into the Atlantic Ocean.

continental shelf, continental slope, continental rise, abyssal plain

When do new oceans form?

when a continent is broken apart by a divergent boundary

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.

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

A piece of oceanic crust is subducted below continental crust.

Which mountain range, formed via continental convergence, developed just before the Appalachians of North America?

Caledonian Mountains

Which mountainous range is not the result of continental collision?

Cascades

How are debris avalanches and flows related?

Debris avalanches are large, rapid flows of rock.

Which response best explains the absence of volcanoes and earthquakes at a passive continental margin?

Earthquakes and volcanoes are rare due to the distance from any active boundaries.

The Ural Mountains were formed by the collision of which continents?

Europe and Asia

How is a fall different from creep?

Falls occur rapidly and in areas with high slope, whereas creep occurs slowly in areas with low slope.

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.

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

The plates move toward each other.

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.

Which is not one of the three broad zones describing the ocean floor? continental slope mid-oceanic ridge continental margin deep-ocean basin

continental slope

What causes melting of material under divergent plate boundaries?

decompression of rock

Which of the following are classifications describing how rock and other material move downslope?

fall, slide, slump, creep, flow

Which type of mass movement event requires the addition of water?

flow

What type of tectonic activity led to the formation and uplift of the Andes on the western margin of the South American Plate?

formation of a volcanic arc

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? CHOOSE ALL THAT APPLY. the density of the plate being subducted the amount of water in the plate being subducted the depth of the water over the plate being subducted the composition of the plate being subducted the age of the plate being subducted

the age of the plate being subducted AND the density of the plate being subducted