Plate Tectonics: Key Concepts, Evidence, and Plate Boundaries

Who proposed the concept of Pangea?

Alfred Wegener

What did Alfred Wegener suggest about the continents?

He proposed that continents were once connected in a supercontinent called Pangea.

Why did Wegener's idea face skepticism?

He incorrectly suggested that continental plates plowed through oceanic plates.

What evidence supported the development of the plate tectonics theory?

Fossil distribution and the discovery of mid-ocean ridges.

What does paleomagnetism reveal about oceanic rocks?

It shows symmetrical patterns on either side of mid-ocean ridges, indicating seafloor spreading and plate movement.

What is the relationship between the age of rocks and distance from mid-ocean ridges?

Rocks at mid-ocean ridges are the youngest, and their age increases with distance from the ridge. This supports the idea of new crust forming at ridges and pushing plates apart.

(red- youngest

blue- oldest)

How fast do tectonic plates move?

About as fast as fingernail growth.

Where do earthquakes commonly occur?

At plate boundaries due to interactions like collisions, separations, or sliding past each other. 

What are the three types of plate boundaries?

Divergent, convergent, and transform boundaries.

What happens at divergent boundaries?

Plates move apart, creating rifts or mid-ocean ridges.

What occurs at convergent boundaries?

Plates collide, with oceanic plates being forced under continental plates, leading to volcanic activity.

What is a transform boundary?

A boundary where plates slide past each other, causing earthquakes.

What is an example of oceanic-oceanic convergence?

One oceanic plate is forced under another, creating volcanic island arcs like the Aleutian Islands.

What are hotspots in geology?

Volcanic regions fed by hot mantle plumes that remain stationary while tectonic plates move over them.

Give an example of a hotspot.

The Hawaiian Islands or Yellowstone Park.

What drives plate tectonics?

Convection currents in the mantle.

How do convection currents affect tectonic plates?

Hot material rises, cools, and then sinks, creating a flow that moves tectonic plates.

occurs in the upper mantle in a slow creeping motion. It breaks the lithosphere into plates and moves them.

What is the significance of the Ring of Fire?

It is a major earthquake zone around the Pacific Ocean.

What causes California's frequent earthquakes?

The San Andreas Fault, where plates slide past one another.

The region where two lithospheric plates meet?

Plate boundaries

Which layer of the Earth consists of tectonic plates?

Lithosphere

Tectonic plates "float" on

the asthenosphere

Mountains form from...

collision of tectonic plates

This is the driving force behind the movement of tectonic plates..

mantle convection currents

A land feature that is produced at a convergent boundary is?

a volcano

What is the name of the area where one crust slides underneath another

subduction zone

The outer layer of the Earth is called the ______________.

crust

A divergent boundary occurs when plates ....

move away from each other

During sea floor spreading, molten material rises up from the mantle...

at the mid ocean ridges

The area around the pacific plate where boundaries form is called...

ring of fire

The Himalayas in Asia are an example of what type of plate boundary?

continent-to-continent convergent

The San Andreas Fault in California is known as an active earthquake area. What type of boundary is it?

transform

Compare oceanic and continental crust.

Oceanic crust is more dense and made up of dense substances like basalt.

Continental crust is less dense and is made up of sand and granite.

What type of boundary is shown in the diagram?

divergent

What type of boundary is shown in the diagram?

Slide/Transform

What type of boundary is shown in the diagram?

convergent

Observe this diagram of a plate boundary. Which statement BEST describes what is happening?

the denser oceanic crust is subducting under the less dense oceanic crust.

Earthquake epicenters (center of where the earthquake started) were mapped for a 35 year period in the diagram above. The black dots indicate these epicenters. The black dots appear along what feature on Earth?

plate boundaries