By Trista L. Pollard /
1Before you pick up that rock, you should know that it has traveled a long way. In fact, rocks are the reason we have solid parts of our planet that are constantly regenerating. It is amazing that we take these important substances for granted. If you were to examine rocks closely, you would observe more than one mineral or solid organic matter within its internal structure. You may also observe noncrystalline substances like glass as part of the rock's composition. Geologists are the scientists who classify rocks and analyze the processes that form rocks on our planet. Rocks also give scientists information about the environments where they were formed. Since rocks are a huge portion of the Earth's crust, it is important for scientists to understand how they form.
2There are three major types of rocks called igneous, metamorphic, and sedimentary. Igneous rocks form as a result of volcanic activity. In fact, the word igneous is Latin meaning "from fire." When magma cools and hardens, igneous rock is born. Once molten rock reaches the Earth's surface it is referred to as lava.
3Sedimentary rock forms after the processes of erosion, deposition, and cementation occur. As the wind and waves beat on the Earth's surface, rocks are broken down into smaller particles through erosion. These smaller particles are from every type of rock. Once these rocks, along with mineral crystals and organic materials, are broken down, they are called sediment. Rivers and streams, huge transporters of sediment, move these materials and deposit the sediment in other areas. The deposited sediment becomes compressed as more layers are added. Eventually, this compression causes the sediment to become cemented or glued together and to harden. Through these processes, sedimentary rock is formed.
4The last type of rock, metamorphic, is formed from extreme pressure and heat and chemical changes. Before this process, metamorphic rocks begin as other types of rocks. Once these forces and processes are applied, metamorphic rocks are produced. Metamorphic means "changed form." All three types of rocks have a special quality: they can change into any of the other three types of rocks and into other forms of themselves.
5The rock cycle is similar to other cycles on our planet. Matter and energy flow throughout this cycle as they do with other Earth cycles. Heat from inside our planet is responsible for creating igneous and metamorphic rock. Weathering and erosion on the Earth's surface powered by the sun produce sedimentary rock. Through the rock cycle, scientists see how the three types of rocks are linked to each other through our planet's energy processes. Rocks experience different geologic forces and processes inside the Earth and on its surface. This is the reason rocks can change into any of the other three types of rocks. Let's enter this cycle with igneous rock.
6Igneous rock on the Earth's surface is changed into sediment through erosion, deposition, and cementation. This sediment is then cemented into sedimentary rock. If the sedimentary rock is exposed to changes in temperature and pressure, it may change into metamorphic rock. The metamorphic rock can be changed into magma if extreme temperatures and pressures exist. The cycle continues with the formation of new igneous rock when the magma cools. This can occur through volcanic eruptions above or below the Earth's surface.
7After studying the rock cycle, scientists believe that our planet's continental crust has gone through the rock cycle many times throughout Earth's history. This helps to build up our planet's surface. Understanding the steps of the rock cycle gives scientists more information about how our planet's crust regenerates over time.
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Pebbles to Mountains
1. / Based on context clues, what does regenerating mean?/ 2. / True/False: Molten rock that reaches the Earth's surface is called magma.
3. / Explain how the rock cycle similar to the Earth's other cycles.
/ 4. / It takes tremendous pressure and heat to change existing rock into ______.
Metamorphic rock
Sedimentary rock
Mafic rock
Igneous rock
5. / Explain how the processes of erosion, deposition, and cementation affect the rock cycle.
/ 6. / What are the external processes that power our planet's rock cycle?
Name ______/ / Date ______
Pebbles to Mountains
7. / Which of the following statements are true?The rock cycle is only powered by the internal forces inside the Earth.
Compression of sediment causes the sediment to become cemented and to form sedimentary rock.
Metamorphic rock can be changed into magma when extreme pressures and temperatures do not exist.
Wind is the major transporter of sediment on our planet.
/ 8. / What if one type of rock was missing from the rock cycle. How would the absence of this rock affect the Earth's crust and other geologic formations on our planet?