Study of physical features of surface of earth, underlying structures, and processes that created and continue to modify them. Cooled and solidified magma is called igneous rock. Size of crystals in igneous rock reflects the rate at which magma cooled. If cooled quickly (days to decades) crystals are so small they can"t be seen with microscope (basalt, dark, heavy, contain iron) usually produced from volcano. If cooled slowly (millions of years) crystals can be seen by human eyes. Granite, lighter in weight and colour, make up continental plates. Weathering: process in which solid rock is broken down or decomposed through exposure to various physical, biological, or chemical agents. Erosion: process in which sediments and minerals produced through weathering are moved to a different location by gravity, wind, water, and so on. Sedimentary rock is sediment compacting together from weathering and erosion. Sandstone: made from sand-sized sediments and shale: made from clay and silt-sized sediments are classic variety.