Chapter 2 Practice questions

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 lithosphere?

Some of the mantle is contained within a smaller 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.

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

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

a single volcano

What are differences between a mid-ocean ridge and a hotspot?

Mid-ocean ridges are formed when a divergent boundaries are pushed apart, creating rift valleys and eventually ridges on the ocean floor where magma wells up to form new crust and forms a mid-ocean ridge. They occur at plate boundaries. Hot spots are spots where a tectonic plate is moving over a mantle plume and are responsible for creating islands like Hawaii and volcanoes like Yellowstone. They occur in the middle of tectonic plates. The main differences between hot spots and mid-ocean ridges are, what mid-ocean ridges create at the bottom of the ocean and hotspots create at the top of the ocean; and mid-ocean ridges occur at the edges of tectonic plates while hot spots occur in the middle of tectonic plates.

Determine the Wilson cycle stage for the Atlantic Ocean or the Red Sea, noting the features and processes that support your answers.

The Atlantic Ocean is in its mature stage. You can tell because its edges reach between the continents, a couple being North America and Africa. If you look at a map of the Atlantic ocean, you will also see ridges going down its center (called the Mid-Atlantic Ridge) meaning it has exited the juvenile stage (perhaps relatively recently) and may still be spreading. The Red Sea is in its juvenile stage. You can tell because it is part of a rift valley, with part of it going down its center, and was formed recently during the movement of Africa away from Arabia. Its 2 halves opened up 30 million and 20 million years ago. It is still spreading at a rate of 15mm per year.

Which of the following lines of evidence did Alfred Wegener use to support the concept of drifting continents?
a. Evidence of glaciers in areas that are now tropical
b. The composition of meteors from outer space
c. The distribution of species of fossils
d. The way the shapes of the continents fit together like pieces of a jigsaw puzzle
e. The pattern of similar mountain belts on different continents

a, c, d, e

Why does the sea floor have a striped pattern of magnetic anomalies that is symmetric with respect to the mid-ocean ridge?
a. The ocean floor is spreading apart, and new sea floor is forming.
b. The igneous rock of the ocean floor preserves Earth’s existing magnetic field as the rock cools.
c. The polarity of Earth’s magnetic field experiences reversals.
d. The reversals occur as existing ocean crust is remagnetized during reversals.
e. Marine organisms that live on the sea floor have caused this pattern.

a, b, c

Of the following statements about ocean crust, which is/are true?
a. Ocean crust is destroyed at deep sea trenches.
b. Ocean crust is destroyed at transform faults.
c. Ocean crust is created at transform faults.
d. Ocean crust is created at deep sea trenches.
e. Ocean crust is destroyed at the mid-ocean ridge.
f. Ocean crust is created at the mid-ocean ridge.

a, f

Where are most modern divergent plate boundaries found?

at mid-ocean ridges

Where do most divergent boundaries originate?

within continents

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

normal faulting

What causes melting of material under divergent plate boundaries?

decompression of rock

When do new oceans form?

when a continent is broken apart by a divergent boundary

The flat top of a guyot or tablemount in deep water is evidence that __________.

the seamount was once at the surface of the ocean, but is now submerged due to plate movement and erosion when it was near sea level.

A trench and a chain of volcanoes known generally as a volcanic arc are always present where there is __________.

subduction

Iceland is located on what type of plate boundary?

Divergent