Restless Earth Flashcards
What is the crust?
The outer layer of the earth.
What is a plate?
A section of the earths crust.
What is a plate margin?
The boundary where two plates meet.
What is the mantle
The dense, mostly solid layer of the earth between the outer core and the crust
What are convection currents?
The circular currents of heat in the mantle
What are the characteristics of the oceanic crust
Newer -most less than 2 million years old
Denser
Can sink
Can be renewed and destroyed
What are the characteristics of the continental crust
Older- most over 1500 million years old
Less dense
Cannot sink
Cannot be renewed or destroyed
What is the structure of the earth?
Crust - outer
Mantle
Outer core
Inner core - inner
What is a destructive plate margin?
- 2 plates moving towards each other
- 1 plate slides under the other (oceanic under continental)
- Volcanoes and earthquakes can occur*
What is a constructive plate margin?
- 2 plates moving apart
* magma forces its way through cracks to form volcanoes*
What is a conservative plate margin?
- 2 plates slide alongside each other (same or opposite direction)
- sliding alongside causes pressure to be built up causing earthquakes*
What is a collision plate margin?
- 2 of the same type of plate move towards each other
* fold mountains*
Characteristics of composite volcanoes
- Steep slope, narrow base
- Eruptions infrequent and often violent
- Often have secondary cones made of lava and ash
Characteristics of shield volcanoes
- Wide base, gentle slopes
- Low rounded peak
- Layers made of running lava and little ash
- Eruptions frequent but non violent
What are fold mountains?
Large mountain ranges where rock layers have been crumpled as they have been forced together. They have anticlines and synclines