51) The Himalayan Mountains the tectonic product of a collision : 2086400
51) The Himalayan Mountains are the tectonic product of a collision between India and Eurasia that began in Eocene time and still continues.
52) An extensive, late Paleozoic glaciation affected southern India, southern Africa and southeastern South America.
53) The oldest rocks of the oceanic crust are found in deep ocean trenches far away from active, mid-ocean ridges.
54) Seafloor spreading rates can be estimated if the geologic ages of the magnetic field reversals are independently known.