Geology Chapter 4 Review

Where in the earth do convection currents occur?

In the asthenosphere

A plate boundary at which one plate slides under another is called a transform fault boundary.

False

A rift valley is an example of a suspect terrane.

False

Alfred Wegener hypothesized that continents are fixed and unable to move.

False

All Mid-Atlantic Ridge rock samples examined have proven to be older than the oldest-known continental rocks.

False

The earth's oldest rocks are found along the Mid-Atlantic Ridge.

False

The magnetic orientation of molten rock from a mid-ocean ridge will always reflect a reversed polarity of the earth's magnetic field at that time.

False

The theory of plate tectonics states that the earth's crust is made up of a single massive plate.

False

What evidence found in tropical regions of Southern Africa and South America most strongly supports the theory that the continents were once joined?

Glacial debris

Which property of iron-bearing rocks provided evidence for the hypothesis of seafloor spreading?

Magnetic Orientation

When examining rocks from both sides of the Mid-Atlantic Ridge, scientists found evidence for the phenomenon of:

Magnetic reversal

Which theory is most directly supported by the discovery of rocks similar in age and type in the areas shaded on the map?

Plate tectonics

Scientific evidence indicating that convection currents move the plates has been found by studying:

Rift valleys

What is the term for a small piece of land that is scraped off descending ocean floor at a subduction zone?

Terrane

A fault formed at the point where two plates slide past each other is called a _________________.

Transform

Fossil records provide a clue to earlier positions of lithospheric plates.

True

Island arcs form along convergent plate boundaries.

True

Magma is the molten rock that wells up through fissures in the earth's crust.

True

Many scientists believe that lithospheric plate movement is caused by temperature differences in the mantle.

True

Movement of the earth's crust away from an oceanic ridge is called seafloor spreading.

True

The Mid-Atlantic Ridge is an example of a divergent plate boundary.

True

The magnetic orientation of a rock is determined when the rock solidifies.

True

The similar ages and types of rocks from Western Africa and eastern Brazil support the theory of continental drift.

True

The theory of plate tectonics explains how some coastal mountain ranges may have been formed.

True

Which scientist first proposed that the continents were once joined in a single landmass called Pangea?

Wegener

According to the theory of continental drift, the eastern coast of South America was once joined to what continent?

Africa

Which of the following may result from the collision of one plate with another?

A convergent boundary

The Palo Alto Hills are probably an example of:

A suspect terrane

Paleomagnetism of the ocean floor is used to identify the:

Approximate time the rock cooled and hardened

In which layer of the earth do convection currents occur?

Asthenosphere

The earth's layer of solid rock that flows under pressure is called the:

Asthenosphere

The layer of plastic rock beneath the lithosphere is called the __________________.

Asthenosphere

The theory of suspect terranes provides an explanation of how:

Continents form

Many scientists believe that the movement of lithospheric plates is caused by _______________ ________________.

Convection Currents

What do scientists think is the cause of the movement of the earth's plates?

Convection Currents

The type of collision that occurs when two lithospheric plates coverage is determined primarily by plate:

Density

Seafloor spreading occurs at which of the following plate boundaries?

Divergent

What type of plate boundary causes extensive volcanic activity in Iceland?

Divergent Plate Boundaries

Seafloor spreading occurs at:

Divergent boundaries

Iceland is growing due to its location on what geologic feature?

Mid-atlantic Ridge

As rock moves away from mid-ocean ridge, it is replaced by:

Molten rock

What two types of crust make up the surface of the earth?

Oceanic & Continental

What is the name for the huge landmass that Wegener believed covered much of the earth 200 million years ago?

Pangea

The theory that proposes a possible explanation of why and how continents move is called the theory of __________ ______________.

Plate Tectonics

Which theory states that new land is added to continental margins at subduction zones?

Seafloor Spreading

The region along a plate boundary where one plate is forced under plate is called a:

Subduction zone