Chapter 17

Earth's Interior

average density of planet: 5-6 g/cm3

average density of surface rocks: 2.5-3.0 g/cm3

the internal structure :

-crust: continental and oceanic lithosphere

-mantle: upper

Asthenosphere

lower

-core: outer (liquid)

inner ( solid)

Seismic Waves

-refraction

-reflection

-discontinuities: marked changes in the velocity of seismic waves indicating a boundary between different material or their properties

-Moho-discontinuity: boundary of crust and mantle

Compositions:

crust: -oceanic: mostly basalt and gabbro, 3.0 g/cm3, 7.00 km/sec

-continental: "granitic", 2.7 g/cm3, 6.75 km/sec

mantle: upper, transition, lower;

peridotite, diff. velocities

core: -inner: solid, 12.6 to 13 g/cm3, Fe with some Ni

-outer: liquid, 9.9 to 12.2 g/cm3, Fe with silicon, sulfur, oxygen, nickel...

Geothermal Gradient

temperature increases with depth, on average 25 degrees C each km (near surface)

heat flow: ability to conduct heat, energy is lost at surface, but generated at depth (radioactive decay)

- Gravity

- Isostacy

-The Magnetic Field