the earths layers and evidence
- Created by: emma may ellen
- Created on: 21-01-19 11:10
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- layers of the earth + evidence
- crust
- the nature of the crust is well known from direct observation.
- oceanic crust is very different from continental crust.
- Moho discontinuity
- a distinct and clear boundary marking a change of rock type and density.
- the p and s waves velocity suddenly decreases
- upper mantel
- the upper mantel is solid
- the main rock type is peridotite
- the upper mantel consists of solid silicates, less dense than the lower mantel
- s waves can travel through the mantel
- low velocity seismic zone
- 100-250km - 5% molten
- the lower mantel
- solid due to the increasing pressure, causing the rock to become more rigid and incompressible
- the mantel is made out of the same silicate material as stony meteorites
- s waves can travel trough the mantel
- both p and s waves steadily increase velocity with depth
- the Gutenberg discontinuity
- a distinct and clear boundary marking a change of mineral from metallic iron nickel to silicate material.
- there is also a change in state between the liquid outer core and the solid lower mantel
- the p wave velocity suddenly decreases and the s waves stop altogether
- the outer core
- the outer core is liquid and reduces rigidity
- the pressure in the outer core is less than in the inner core, allowing liquid to exist
- s waves do not travel through the outer core which shows that it must be a liquid
- p waves slow down due to the rigidity
- lithosphere
- the crust and the region of the upper mantel above the asthenosphere is called the lithosphere
- the Lehman discontinuity
- a phase boundary of about 100km where the rock changes from liquid in the outer core through liquid solid transition to all solid in the inner core
- the p wave velocity increases at the boundary
- inner core
- the inner core is solid because o f the extreme pressure 3600000Ats, compared to 1 at the surface
- the ion of the composition is iron-nickel
- the dencity is more than 12gcm-3
- p and s waves travel through the inner core
- s waves are generated by p waves at the Lehman discontinuity
- iron meteorites
- the earth has a magnetic filed
- crust
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