Structure, state and composition of Earth Flashcards
1
Q
What is the oceanic crust?
A
- Made from basalt
- Density 2.9 g/cm^3
- 5-7km thick
2
Q
What is the continental crust?
A
- Made from granite
- Density 2.7 g/cm^3
- 30-60km thick
3
Q
What is the mantle?
A
- Made from flowing peridotite
- density 3.3 g/cm^3
4
Q
What is the core?
A
- made from iron and nickel
- density 12 g/cm^3
- liquid outer core
- solid inner core
5
Q
What is the order of the layers (hint - lithosphere first)
A
- lithosphere
- 1300 degree isotherm
- asthenosphere
- Gutenberg discontinuity
- liquid outer core
- Lehmann discontinuity
- solid inner core
6
Q
What is some direct evidence for the structure of earth?
A
- rocks from down below at the surface
- eroded mountain roots
- boreholes and mines - boreholes to 12km
- Ophiolites - slice of oceanic crust
- Volcanic rocks with xenoliths
7
Q
What are the main types of waves?
A
- P waves - body waves tell us the interior of earth
- S waves - body waves tell us the interior of earth
- L waves - surface waves will cause most damage to buildings in earthquake
8
Q
What are P waves?
A
- Push waves
- fastest moving
- affected by rigidity and incompressibility
- travels through solids and liquids
9
Q
What are S waves?
A
- Shear waves
- moderately fast
- affected by the rigidity
- travels through solids only
10
Q
What is the Shadow zone?
A
-region of earth that receives no or little seismic waves
11
Q
Why does the shadow zone occur?
A
- seismic waves refract due to changes in wave velocity
- if there is an extreme change in velocity then certain waves may not be transmitted
- can be refracted from boundary
12
Q
What is the P wave shadow zone?
A
- due to a change in solid mantle to liquid outer core
- cause p waves to slow and refract to surface
13
Q
What is the S wave shadow zone?
A
- due to a change from solid mantle to liquid outer core
- doesn’t allow the s waves to propagate through it
