Chapter 5: Plate Tectonics

Divergent boundaries

Forms a rift valley on land, or ocean ridge in the water.

Convergent Boundaries (Continental-Continental)

Forms a vast mountain range, such as the Himalayas

Convergent boundaries (oceanic-oceanic)

Forms an arc of volcanic islands.

Convergent Boundaries (Oceanic-Continental)

A trench and a volcanic arc (on land) are produce

Transform boundaries

Characterized by long faults and earthquakes

What material found in Antarctica suggested that it once had a swampy, tropical climate?

Coal

What was Wegener's hypothesis called?

Continental drift

The Himalayas were formed by which type of boundary?

Continental-continental convergent

How does convection affect seafloor spreading?

Convection currents in the mantle is the main force driving tectonics plate motion. Mantle material is pushed up at the ridge and horizontally outward from the ridge causing the seafllor to spread in opposite directions at the ridge.

The Marianas Trench, Andes Mountains, Himalayan Mountains, and Aleutian Islands are formed as a result of ______.

Convergent boundaries

What counterparts (opposite but of equal importance) of volcanic mountain chains were found from maps generated with sonar data?

Deep-sea trenches

Which of the following geologic events often occurs at a transform boundary?

Earthquake

The following are pieces of evidence that support seafloor spreading, EXCEPT for ____.

Glossopteris and Mesosaurus fossils found on different continents

What is an isochron

Imaginary line or color band that shows rocks that are of similar age

What uses sound waves to detect and measure objects underwater?

Sonar

A magnetometer detects small changes in what?

Magnetic fields

Where are young rocks in the ocean located

Near ocean ridges

What happens along most divergent boundaries?

New ocean crust forms

What plate boundary forms a deep sea trench and volcanic mountain ranges (on land)?

Oceanic-continental convergent

To support his hypothesis, Alfred Wegener did NOT use ______.

Paleomagnetism

Approximately 225 million years ago, the earth's continents were grouped into one landmass called ______.

Pangea

Which theory states that the Earth's crust and rigid upper mantle move in different directions and at different rates over Earth's surface?

Plate tectonics

Magnetic reversals would be impossible to explain if it weren't for ______.

Seafloor spreading

What is theory that explains how new ocean crust is formed at ridges and destroyed at deep-sea trenches

Seafloor spreading

Topography of the ocean floor is mapped by _________.

Sonar

How is magnetism evidence that the seafloor is spreading ?

Symmetrical magnetic stripes were apparent on opposite sides of the ridge. The magnetic stripes were showing rocks that were made when Earth's polarity had reversed. The mirrored stripes of both sides of the ocean ridge can only be explained if the seafloor was created and spreading from the ridge.

Convergent boundaries (oceanic-continental)

The Andes mountains are the result

Convergent boundaries (oceanic-oceanic)

The Marianas Trench is the result.

transform boundaries

Two plates move past each other horizontally

Divergent boundaries

Two tectonic plates are moving apart from one another.

Convergent Boundaries (Continental-Continental)

Volcanic activity is rare here, because the two colliding plates are so thick

What did Wegener conclude from his observations of Glossopteris?

continental rocks containing these fossils were once joined and had a similar climate (tropical)

What is the main force that drives plate movement?

convection currents in the mantle

Which type of boundary is associated with new crustal material?

divergent

Why was Wegener's hypothesis rejected by most other scientists at the time?

he could not explain how or why the continents moved

What are the 3 types of convergent boundaries?

oceanic-oceanic, continental-continental, oceanic-continental

What happens during a magnetic reveal?

the flow in the outer core changes, and Earth's magnetic field flips direction

What is a transform boundary?

two plates moving along side each other