Geology
From the Simple English Wikipedia, the free encyclopedia that anyone can change
Geology is the study of the nonliving things that the Earth is made of. Geology is the study of soil and rocks. The people that study Geology are called "Geologists". By studying the soil and rocks that the Earth's surface is made of, Geologists can learn more about the history of the Earth. Some of the important "events" (things that happen) in the Earth's history are floods, volcanic eruptions, and earthquakes. Some Geologists study soil and rocks to find metals and fuels that are underground.
Geology is divided into smaller subjects that just study one part of Geology.
Some of these subjects are:
- Petrology - the study of rocks how they form and where they are from.
- Mineralogy - the study of minerals
- Historical geology - the history of the events that shaped the Earth.
- Palaeontology - The study of fossils (the remains of animals from long ago).
- Hydrogeology - the study of water under the surface of the Earth
- Volcanology - the study of volcanoes on land or under the ocean.
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[change] Types of rock
Rocks can be found in all sorts of shapes and colours. Some are very hard and some are soft. Some rocks are very common, while others are rare. However, all the different rocks belong to three categories or types, Igneous, Sedimentary and Metamorphic.
[change] Igneous rock
Igneous rock is rock that has been made under the ground by volcanic action. Igneous rock is made when the hot molten (melted) "magma" or "lava" which is under the surface of the earth cools down and sets hard. This often happens after a volcano has erupted, and lots of hot magma has spilled down the sides of the volcano. Sometimes the runs in streams, and sometimes its spreads out across the land. Sometimes the magma doesn't come out through a volcano, but spreads underground between layers of rock. A well-known igneous rock is pumice.
[change] Sedimentary rock
Sedimentary rock is rock that has been made from "sediment". "Sediment" is all the pieces, large and small, that get left behind by water. Sediment can be made from sand, gravel and the bodies and shells of animals. The sediment gets dropped in a layer at the bottom of a river or sea. As the sediment piles up, the lowers layers get squashed together. Slowly they set hard into rock. Some sedimentary rocks are made of just one type of sediment, all about the same size, such as sand. Other sedimentary rocks will have large and small lumps, and pieces made of different types of rock. Well-known sedimentary rocks are sandstone and limestone.
[change] Metamorphic rock
Metamorphic rock is rock that has been changed. The word "metamorphosis" means "change". Sometimes an igneous, or a sedimentary rock can be heated, or squashed under the ground, so that it changes. Metamorphic rock is often harder than the rock that it was before it changed. One well-kknown metamorphic rock is marble which is valued for its different colours, and because it can be carved and polished. Slate is a metamorphic rock that is a useful building material.
[change] Faults
All three kinds of rock can be changed by being bent by forces in the earth. When this happens, faults (cracks) appear in the rock. Geologists can learn a lot about the history of the rock by studying the patterns of the fault lines.
[change] Soil
Soil is the stuff on the ground made of lots of "particles" (or tiny pieces). The particles of soil come from rocks that have broken down, and from rotting leaves and animals bodies. Soil covers a lot of the surface of the Earth. Plants of all sorts grow in soil.
To find out more about types of rocks, go to Rock (geology). To find out more about soil, go to Soil.
[change] Principles of Geology
Geologists use some simple ideas which help them to understand the rocks and soil that they are studying. These ideas are called the "Principles of Geology".
- Understanding the past- Geologist James Hutton said "The present is the key to the past". He meant that the sort of changes that are happening to the Earth's surface now are the same sorts of things that happened in the past. Geologists can understand things that happened millions of years ago, by looking at the changes that are happening today.
- Horizontal layers- The layers in a sedimentary rock must have been flat when they were made.
- The age of the layers- Layers at the bottom must be older than layers at the top, unless all the rocks have been turned right over.
- The age of the lumps- In sedimentary rocks that are made of sand or gravel, the sand or gravel must have come from an older rock.
- The age of faults- If there is a crack or fault in a rock, then the fault is not as old as the rock. Sometimes rocks are in lots of layers. A geologist can see if the faults go through all the layer, or only some. This helps to tell the age of the rocks.
- The age of a rock that cuts through other rocks- If an igneous rock cuts across sedimentary layers, it must be younger than the sedimentary rock.
- The age of fossils- A fossil in one rock must be about the same age as the same type of fossil in a different rock.
 Layers of sedimentary rock |
 A fault cutting through older sedimentary rocks |
 Sedimentary rock made from white pieces of older rock, that were broken up and mixed with red sand at the bottom of a river. |
 The Zimbabwe Great Dyke: A big band of igneous rock cuts between sedimentary rocks. This picture was taken from a satellite. |
 Beaches are interesting places to study Geology, |
 ....so are caves. |
 This rock-face in Norway has a very interesting history to tell the Geologist. |
 This rock-face in France contains the mineral Mica. |
 A simple, important tool for the Geologist. |
 Geologists often use drills like this to take "samples" of stone from the Earth. |
 A young Butcher Bird is standing on a box of samples of rock that have been drilled from underground. |
 Geologists look at some samples of rock, to find minerals for mining. |
 A map showing the geology of South East England. This area has been studied for hundreds of years. |
 A map showing the different soils and rocks under the Southern Ocean. Geologists are finding new information about this area. |
 This map shows the main "plates" of the Earth's surface and which way they are moving. |
 This diagram shows what happens when a volcano erupts under the ocean |
[change] See also
- Geography is the study of the Earth and its features, its inhabitants, and its phenomena.
- Zoology is the study of animals
- Botany is the study of plants and fungi
- Astronomy is the study of space
- Microbiology is the study of micro-organisms
