BMEN 515 Lecture Notes - Radionuclide, Continental Drift, Cyanobacteria
Document Summary
Half of the remaining radioactive material of the radioisotope decays. The decay of potassium-40 to argon-40 has been used to date most of the ancient events in the evolution of life. Fossils in the adjacent sedimentary rock that are similar to those in other rocks of known ages provide additional clues. Radioisotopes dating of rocks, combined with fossil analysis, are the most powerful method of determining geological age. Earth"s crust consists of a number of solid plates approximately 40km thick, collectively make up the lithosphere. It floats on a fluid layer of molten rock (magma) Magma circulates b/c heat produced by radioactive decay deep in earth"s core sets up convection currents in the fluid. The plates move b/c magma rises and exerts tremendous pressure. Where plates are pushed together, either they move sideways past each other, or one plate slides under the other, pushing up mountain ranges and carving deep rift valleys (underwater known as trenches).