Geology is the study of the earth. It includes the study of rocks and how they were formed. It also includes the study of the different layers of the earth and different landforms, such as mountains. A person who studies geology is a geologist.

Parts of the Earth

    There are three main parts to the earth: the core, mantle, and crust. The core is at the center of the earth. The mantle is made of melted rock. The crust floats on the mantle. The crust is broken into big sections of earth called plates. The crust is much thicker on the continents than it is under the oceans. Geologists think that the inner core is a solid ball of iron and nickel and the outer core is melted iron and nickel.

Plate Techtonics

    The study of how the plates move over and under each other and push against each other is called Plate Tectonics. The continents move around on top of the plates. The pressure of the plates pushing against each other causes deep cracks in the rock called fault lines. The fault lines are places that are likely to have mountains, active volcanoes, hot springs, geysers, or earthquakes. Many active volcanoes are found around the Pacific Ocean in the Ring of Fire.

Mountains

    There are many kinds of mountains. A volcano erupts when hot magma from the mantle pushes through a crack in the crust. Not all volcanoes make lava. Some only make hot gases and ashes. Mount Vesuvius, Mt. Saint Helens, and Krakatoa are some famous volcanic mountains. Sometimes the plates push against each other and the earth moves up to make a block mountain. Sometimes the plates push together and make ripples in the crust. The Appalachian Mountain chain of North America is an example of a folded mountain. Sometimes the magma pushes up and a large part of the crust bulges to make a dome mountain. Sometimes a large section of earth pushes straight up to make a plateau.

Rock Types

    There are three main types of rocks. Igneous rocks are made of melted rock from the mantle. Sedimentary rocks are made by layers of sand, dirt, shells, or other materials piling on top of each other on the ocean bottom over a long period of time. The layers push together from the weight of the sediments and the ocean water to form rock. When heat or pressure changes an igneous or sedimentary rock into a new kind of rock, this rock is called a metamorphic rock.

    Rocks are made of minerals. When we see different colors or shiny specks in a rock we are seeing the different minerals in the rock. Geologists can identify a rock by what color it is, how it breaks into pieces, how hard it is, and how it reacts to certain chemicals.

Fossils

    Fossils can sometimes be found in rocks when a plant or animal was covered in such a way that it did not rot normally. Many fossils can be found in coal and in sedimentary rocks. Coal formed from layers of plants, Oil formed from layers of animals. Natural gas pockets are found in the rocks above coal and oil deposits. We depend on the fossil fuels coal, oil, and natural gas.

Caves

    Caves form in limestone rocks. Rainwater combines naturally with the carbon dioxide in the air to make a very weak acid. The rainwater carries this weak acid into the ground. This acid helps to dissolve the limestone. Over millions of years the hole under ground becomes a cave. The dripping water makes stalactites and stalagmites. If the roof of the cave falls in we call this a sinkhole.

The Rock Cycle