As the magma cools and solidifies, the convection currents will stop and the Earth will become geologically dead.
Longitude is the measurement east or west of the prime meridian. Longitude is measured by imaginary lines that run around the Earth vertically (up and down) and meet at the North and South Poles. ... Each meridian measures one arcdegree of longitude. The distance around the Earth measures 360 degrees.
The mesosphere is your answer.
