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Margaret has taught many Biology and Environmental Science courses and has Master's degrees in Environmental Science and Education.
The next time you take a walk, think about what you are walking on. What is the earth made of? The outermost layer of the earth is known as the crust, and this layer is responsible for the majority of life on Earth. It supports the growth of plants, the survival of animals, the structure of our land, and the development of the human civilization.
The earth's crust has four main components, which are referred to as Earth's materials. These materials include minerals, rocks, soil and water. It is the combination of these materials that makes life on Earth possible.
Let's start with minerals and look at them in more depth. Minerals are naturally occurring inorganic solids that have a crystalline structure and definite chemical composition. Minerals are referred to as naturally occurring because they are formed though natural geological processes. Minerals are non-living and have a crystalline structure, meaning the atoms that make up the mineral are arranged in an orderly, three-dimensional pattern that repeats itself. Minerals are said to have a definite composition because all minerals are made up of specific proportions of certain elements.
There are over 4,500 different minerals identified on Earth. Each has a unique combination of crystalline structure and chemical composition. Salt is an example of a mineral. If you look closely at a grain of salt, you will see that it is a solid that has a specific shape and pattern.
Now that we know what minerals are, we can discuss rocks. Rocks are defined as naturally formed aggregates of minerals or mineral-like substances. Rocks can be made up of one type of mineral, several minerals, or no minerals at all. Limestone is a rock that is comprised of the mineral calcite. Many crystals of calcite are cemented together to form the limestone. Granite is a rock that is comprised of several different minerals, including quartz, biotite, potassium feldspar, and plagioclase feldspar. Coal is an example of a rock that isn't comprised of any minerals, but instead is made of decomposed organic matter.
Rocks are often classified by how they are formed. The three types of rocks are sedimentary, igneous, and metamorphic. Sedimentary rocks are formed by the accumulation of sediment that is deposited over time. Igneous rocks are formed when molten magma cools and solidifies. Metamorphic rocks are formed when an existing rock changes due to heat, pressure, or some other physical force.
Soil is another of Earth's materials. Soil is a mixture of decomposed organic matter and broken down rocks and minerals. The decomposed organic matter is mainly dead plant material. The broken down rocks and minerals are formed when larger rocks and minerals are made into smaller pieces due to erosion or weathering. On average, soil is made up of 45% rock and mineral pieces, 5% decomposed organic matter, and 50% pore space. The rock and mineral pieces are what plants attach their roots to in order to anchor themselves in place. The decomposed organic matter is responsible for producing nutrients for plants and increasing water retention. The pore spaces in soil are very important because they allow water and air to circulate through the soil. The water and air transport nutrients and carbon dioxide, which are essential for the growth of plants.
The final component of Earth's crust is water. Water is defined as a clear, colorless, odorless, and tasteless liquid, which is comprised of hydrogen and oxygen. The earth is often called the 'Blue Planet' because the majority of its surface is covered in water. Naturally, water comes in two different forms, which are saltwater and freshwater. On Earth, 97.2% of water is considered saltwater because it has a high level of saline. The remaining 2.8% of the total volume of water on Earth is freshwater and can be used by humans and most other organisms. Of all the freshwater on Earth, most of it is stored in the form of ice. The rest is stored as groundwater, which is under the surface, and a small amount is stored as surface water, which is water in lakes, streams, and rivers. Water is a very valuable resource because every living thing needs it to survive.
Now, let's review the earth's materials, which are the main components that make up the outer crust of the earth. These four materials include minerals, rocks, soil and water.
Minerals are naturally occurring inorganic solids that have a crystalline structure and definite chemical composition. Rocks are naturally formed aggregates of minerals or mineral-like substances. Rocks can be made up of one type of mineral, several minerals, or no minerals at all. The three types of rocks are sedimentary rocks, which are formed by the accumulation of sediment that is deposited over time, igneous rocks, which are formed when molten magma cools and solidifies, and metamorphic rocks, which are formed when an existing rock changes due to heat, pressure, or some other physical force. Soil is a mixture of decomposed organic matter and broken down rocks and minerals. Soil also contains important pore spaces that allow water and air to circulate. The final material is water, which is a clear, colorless, odorless, and tasteless liquid, which is comprised of hydrogen and oxygen. The majority of water on Earth is in the form of saltwater and a small amount is freshwater.
All four materials are very important alone, but together they are even more impressive. They interact with each other and the combinations of these materials are what make life on Earth possible.
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Geology 101: Physical Geology21 chapters | 128 lessons | 13 flashcard sets
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