THERMAL EVOLUTION OF OCEANIC LITHOSPHERE

OCEANIC LITHOSPHERE COOLS AND THICKENS AS IT MOVES AWAY FROM THE RIDGE

ISOTHERMS - LINES OF CONSTANT TEMPERATURE - DEEPEN AS THE SQUARE ROOT OF PLATE AGE

SIMILAR SQUARE ROOT OF TIME BEHAVIOR OCCURS FOR COOLING OF A LAVA POND OR ANY OTHER PROCESS DESCRIBED BY DIFFUSION

THUS THE LITHOSPHERE CAN BE THERMALLY DEFINED AS THE REGION BELOW (COOLER THAN) SOME ISOTHERM ABOUT 1300 DEGREES

FOR AGES OLDER THAN ABOUT 70 MY COOLING STOPS, BECAUSE HEAT ADDED FROM BELOW BALANCES THAT LOST AT THE TOP, SO ISOTHERMS NO LONGER DEEPEN AND PLATES REACH A FINAL THICKNESS