two types of seismic waves :
o longitudinal pressure waves
can spread into both solids and liquids.
o have their direction of motion refracted by interior density
o transverse waves
can spread into solids but not into liquids Structure of the Interior
The crust of the earth is approx. 10 kilometers wide
region between the core and the crust : mantle
upper part of the mantle and the crust together : thelithosphere.
underneath the lithosphere (crust and upper mantle ) is a plastic region
consistency : aesthenosphere
approx. 1 billion years ago the Earth was melted by heat arising from