Study of the physical features of the surface of the earth, their underlying structures, and the processes that created and continue to modify them. Age of a rock formation is a direct indication of the process that formed it. Magma that is brought close to (or at) the surface of the earth, cools into igneous rock. Size of crystals in this rock reflects the rate at which the magma cooled. They contain iron and other heavy metals (basalt); dark in colour and dense. Produced from volcanic activity; most rocks on the ocean floors are this type. Plutonic/intrusive igneous rocks are lighter in weight and colour than basalt, typically making up continental plates. Weathering: process in which solid rock is broken down/decomposed through exposure to various physical, biological, or chemical agents (aka water, wind, temperature change, and vegetation growth) Some agents break down the rock, others dissolve the minerals in the rock making water hard and ocean salty.