The average geothermal
gradient of the earth is about 25
degrees
The temperature gradient is lower in the mantle
Radioactive heat production is concentrate within the crust
The mechanism of thermal transport changes
form conduction within the rigid lithosphere plates,
to convection in the asthenosphere and the upper
mantle, and this transports the heat differently
Volcanoes bring magma form depth
Mines and Boreholes
Ophiolite suites-ocean crust on land
During the collision of plates, sections of
oceanic crust may be broken off a descending
oceanic plate and thrust onto the edge of the
continental plat, instead of being carried down
into the mantle
They may be exposed to erosion
Indirect
Seismic waves
P and S waves are seismic waves that
travel through the layers of the earth
body waves
faster if the rock becomes more rigid
and more incompressible
slower if the rock becomes more dense
The shadow zone
Where P and S waves cannot pass
Seismic waves are refracted at the Gutenberg discontinuity