By Mayo Clinic Staff. Erectile dysfunction â the inability to get and keep an erection firm enough for sex â is a common problem. You've likely seen advertisements for erectile dysfunction herbs or supplements to increase your sexual performance..
plate tectonics. In geology, a theory that the Earth's lithosphere (crust and upper mantle) is divided into a number of large, plate-like sections that move as distinct masses. See Notes at fault, Gondwanaland, See more at tectonic boundary.
Plate tectonics is the theory that the surface of the earth is broken into larger pieces of crust called plates that ride along on a softer layer of the earth, known as the asthenosphere, which is the upper part of the mantle.ach plate's thickness depends on the type of crust it is made of and the location of the plate. Continental plates can be up to 150 km thick, whereas oceanic plates usually average about 5-10 km thick.