Lesson 2 - Plate Tectonics and Associated Hazards Flashcards
1
Q
What are the 2 types of crust?
A
- Oceanic (sima - silicate + magnesium)
2. Continental (sial - silicate + aluminium)
2
Q
What are the characteristics of the oceanic crust? (6 points)
A
- Very thin, 8km
- Very young, under 200 million years
- More dense vs continental
- Heavy, subducts
- Made up of mainly basalt
- 1200°C
3
Q
Why is the oceanic crust young?
A
It’s constantly being created and destroyed
4
Q
What are the characteristics of the continental crust?
A
- Thicker, up to 70km
- Mainly made up of granite
- Less dense vs oceanic
- Does NOT subduct
- Very old, 1500 million years
5
Q
What does the Moho discontinuity do?
A
Separates crust from upper mantle
6
Q
What is the lithosphere?
A
The collective of the crust and upper rigid layer of the mantle
7
Q
What are the characteristics of the mantle?
A
- Mainly silicate rocks, rich in magnesium and iron
- Rigid top layer = half of the lithosphere
- Mantle extends 2900km with temperature of 5000°C
The rocks in the remainder of the mantle, the asthenosphere, are kept semi-molten.
8
Q
What do the high temperatures in the mantle do?
A
Generate convection currents
9
Q
What are convection currents?
A
.
10
Q
What are the characteristics of the core?
A
- Made up of mainly iron and nickel
- Outer core is semi-molten
- Inner core is solid
- At the centre of the core, 6400km, the temperature is 6200°C
