Question 1

The Sierra Nevada of California and the Coast Mountains of British Columbia are both examples of active Andean orogenic belts.

Accepted Answer

The answer of The Sierra Nevada of California and the...

Question 2

The foothills of the Canadian Rockies, as the most easterly portion, were the first to form in response to deformations on the continental margin.

Accepted Answer

The Canadian Rockies themselves, not the foothills, were the first to form due to the deformation of the continental margin, as the mountains were pushed up by tectonic forces. The foothills formed later as erosion and sedimentation processes reshaped the landscape around the newly formed mountain ranges.

Question 3

In eastern Canada, the innermost edge of the Appalachian's Paleozoic accreted terranes is Logan's Thrust.

Accepted Answer

Logan's Thrust is indeed the innermost edge of the Appalachian's Paleozoic accreted terranes in eastern Canada.

Question 4

An old, eroded Aleutian-type margin would be far more likely to contain significant thicknesses of continental sediments than an active Andean margin.

Accepted Answer

The answer of An old, eroded Aleutian-type margin would be...

Question 5

The Appalachians first started out as a rifted margin when Laurasia split apart in the Cambrian.

Accepted Answer

The Appalachians formed from a series of orogenies (e.g., Taconic, Acadian, Alleghanian) due to continental collisions, not from a rifted margin.

Question 6

The western edge of the prairies is the Front Ranges.

Accepted Answer

The western edge of the prairies is defined by the foothills, not the Front Ranges. The Front Ranges are part of the Rocky Mountains, which lie west of the prairies' foothills.

Question 7

If the earthquakes south of India foretell of an new subduction zone forming there, eventually the Himalayas will gain a volcanic arc on top of the Tibetan Plateau.

Accepted Answer

The formation of a subduction zone and a volcanic arc is a lengthy process that requires the convergence of two tectonic plates. The earthquakes south of India may indicate some movement of tectonic plates, but they do not necessarily lead to the formation of a new subduction zone. Additionally, the Tibetan Plateau is not an active volcanic region, and the formation of a volcanic arc on top of it would require significant changes in the underlying tectonic processes.

Question 8

Volcanic island arcs and granitic, batholithic zones develop along convergent margins on the overriding plate above an oceanic plate sinking into the mantle.

Accepted Answer

This statement is true. Volcanic island arcs and granitic, batholithic zones do indeed develop along convergent margins above subduction zones, where an oceanic plate is sinking into the mantle beneath a continental or another oceanic plate. This is because the subducting plate contains water and other volatiles that are released as it sinks deeper into the mantle, leading to partial melting of the mantle and formation of magma. This magma rises to the surface and generates volcanic activity in the form of island arcs or continental volcanic arcs, while the solidified magma chambers underground form granitic, batholithic zones known as plutons.

Question 9

Microcontinental fragments, island arcs, oceanic plateaus and volcanic island chains plus intervening packages of sediments are all commonly accreted in ocean-continent margin settings.

Accepted Answer

Ocean-continent margin settings are well-known sites of accretion where various types of materials, such as microcontinental fragments, island arcs, oceanic plateaus, and volcanic island chains, are added to the continental margin by tectonic processes. These materials are often associated with sedimentary packages that accumulate between collision zones or along subduction zones. Therefore, the statement is true.

Question 10

The most likely place for a high temperature metamorphic belt along an Andean margin is among the volcanic debris and deformed accretionary wedge materials over the oceanic slab.

Accepted Answer

High temperature metamorphic belts along an Andean margin are most likely to be found in the continental crust above the subducting oceanic slab, where the heat from the subducting slab and associated magmatic activity can cause high-grade metamorphism, rather than among the volcanic debris and deformed accretionary wedge materials over the oceanic slab.

Question 11

India was rifted from Antarctica about 130 million years ago, drifted northwards throughout the Cretaceous and Early Cenozoic, to finally crash into Asia 10 million years ago.

Accepted Answer

This statement is true. India was indeed rifted from Antarctica about 130 million years ago, slowly drifting northwards to eventually collide into Asia 10 million years ago, resulting in the formation of the Himalayan mountain range. This movement is also responsible for the unique geological formations and biodiversity present in the Indian subcontinent.

Question 12

The two most likely locations for sediments to accumulate on an Aleutian margin are in the trench and on the edges of the arc.

Accepted Answer

Sediments tend to accumulate in the trench due to subduction of the Pacific plate beneath the North American plate. Sediments also accumulate on the edges of the arc due to erosion and deposition from rivers and glaciers. Therefore, both locations are likely for sediment accumulation on an Aleutian margin.

Question 13

British Columbia is "accreted terrane central" as it contains more than 39 separate terranes, all accreted during the past 200 million years with the westward motion of North America since the break up of Pangaea.

Accepted Answer

British Columbia is indeed "accreted terrane central" due to the accretion of more than 39 separate terranes over the past 200 million years as North America moves westward since the break up of Pangaea.

Question 14

The Himalayan Mountains and Tibetan Plateau are still rising today as Eurasia slides beneath the Indian subcontinent.

Accepted Answer

The Himalayan Mountains and Tibetan Plateau are rising because the Indian subcontinent is colliding with and sliding beneath the Eurasian Plate, not the other way around.

Question 15

The Himalayan Mountains and Tibetan Plateau are still rising today as the Indian subcontinent continues to be pressed into Asia by the spreading along the Southeast Indian Ridge.

Accepted Answer

The Himalayan Mountains and Tibetan Plateau are still rising due to the ongoing collision between the Indian subcontinent and Asia, which is caused by the spreading of the Southeast Indian Ridge.

Question 16

Terrane accretion generally occurs along a divergent boundary between a continental plate and an oceanic plate.

Accepted Answer

Terrane accretion generally occurs along a convergent boundary, specifically a subduction zone, where an oceanic plate is being forced beneath a continental plate.

Question 17

Adjacent terranes accreted to a continent will generally show similar geologic histories for the time before joining and different geologic histories thereafter.

Accepted Answer

Adjacent terranes can have distinct geologic histories even before accretion, so their histories may continue to differ after joining the continent as well. This is known as terrane heterogeneity.

Question 18

The western two ranges of the Canadian Rockies are mostly underlain by Proterozoic through Paleozoic limestones and shales.

Accepted Answer

This statement is true. The western two ranges of the Canadian Rockies, the Front Ranges and the Main Ranges, are primarily composed of sedimentary rock formations dating back to the Proterozoic and Paleozoic eras. These formations include limestones and shales, as well as sandstones, conglomerates, and other types of sedimentary rocks.

Question 19

Folds and thrust faults in the rocks of the Appalachian region formed in late Paleozoic time when Africa collided with North America.

Accepted Answer

The collision of Africa and North America during the late Paleozoic era led to the formation of folds and thrust faults in the rocks of the Appalachian region.

Question 20

Accretionary wedges develop along subduction zones where sediments and other rocks are scraped off a descending oceanic plate and piled against the leading edge of the overriding continental plate.

Accepted Answer

This statement is true. Accretionary wedges are commonly found at subduction zones and result from the collection of sediments and other rocks that are scraped off the descending oceanic plate and accrete against the leading edge of the overriding continental plate.

Quiz 13: Mountain Building and Continental Frameworks