Geologic Studies Key Terms: It Rocks! - Rocks are constantly Changing, this process is called the “Rock Cycle”. - The study of rocks is called geology. - 1. Sedimentary Rocks: a type of rock which is formed when sediments are left in a lake or sea. Sediments are small pieces of mud or sand which are left in water. When put under great pressure these sediments stick together to form sedimentary rock. - Igneous Rock: a type of hard rock which comes out of the ground as a liquid called magma. (When magma reaches the earth’s surface it is called lava). As it spreads out, it cools and becomes solid igneous rock. - Metamorphic Rock: rock which has been changed in some way usually by being heated or put under pressure. Limestone can be turned into marble by heat and pressure. Other Important Terms Lava: Molten rock that reaches the earth’s surface. Fault: A crack in the earth’s crust. The rocks on either side of this crack move upwards or downwards. Folding: A process in which layers of the earth’s surface are deformed into “folds”. Folding occurs with sideways movement.