12.2 Features of Tectonic Plates Flashcards
What does the existence of mountains, volcanoes, and earthquakes suggests?
It suggests that Earth’s interior is not simply a solid ball of rock.
What did scientists think Earth begin as? When did it start?
They think that Earth began as a molten ball, over 4.5 billion years ago.
What is 3/4 of Earth’s crust made of?
Elements silicon and oxygen, which combine to form group of rocks called silicates.
How many layers is Earth made of?
4
Fill in the blank:
Earth’s outer layer is composed of several large, rigid but mobile chunks of rock known as _______ _______.
Tectonic Plates.
What is the lithosphere made of?
The uppermost mantle, crust, and tectonic plates.
How many tectonic plates are there?
12 major ones, many smaller ones.
What do oceanic plates contain?
It contains the dense rock basalt.
What does the continental plate contain?
Large amounts of granite.
What is the crust made of?
Solid, brittle rock.
What is Earth’s thickest layer?
The mantle.
What is the upper mantle composed of?
Partly molten rock containing iron and magnesium.
What is the lower mantle made of?
Solid, dense material that contains the elements magnesium and iron.
Is the outer core solid or liquid?
Liquid.
What keeps the inner core solid?
The incredible pressure.
What elements are in the core?
Iron and nickel.
What is below the lithosphere?
Asthenosphere
What is the asthenophere?
A partly molten layer in the upper mantle.
Why does the temperature of the asthenosphere vary throughout?
Because of large quantities of radioactive elements such as uranium occur in some areas.Radioactive decay heats up the mantle in these spots.
What’s the result of the radioactive decay?
A convection current results as the hotter, less dense material in the mantle. It rises, cools and sinks again, only to be reheated.
What is the process I just described call? (The process when the material gets hot in the mantle by radioactivity, rises, cools, than gets reheated again.)
Mantle Convection.
What do scientists hypothesize about the mantle convection?
That it is one of the driving forces behind plate movement.
Where do rising currents of magma reach Earth’s surface?
At a spreading centre.
What is a spreading centre in a ocean called?
It’s called a spreading ridge or oceanic ridge.
What is a spreading centre on land called?
A rift valley.
What happens when magma reaches the surface?
It becomes new rock.
What happens as new material at a ridge or rift valley pushes older material aside? What is this process called?
The tectonic plates move away from the ridge. The process is called ridge push.
If two plates collide, which one will pushed down?
The older and denser one.
Define subduction.
The action of one plate pushing below another.
What are areas of subduction called?
Subduction zones
What happens at a subduction zone?
Large earthquakes and volcanic eruptions.
Define slab pull.
The pulling of a tectonic plate as its edge subducts deep into the mantle.
