THE ROCK CYCLE – It has no start. It has no finish. Rocks that get broken up, This cycle will replenish!.
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The Earth is active. Even more so than an antsy 6th-grader! In fact, as you are reading this: Volcanoes are erupting. Earthquakes are shaking. Mountains are being pushed up and being worn down. Rivers are carrying sand and mud to the sea. Huge slabs of Earth’s surface, called tectonic plates, are slowly moving – about as fast as your fingernails grow.
The three main types of rock in the Earth’s crust are igneous, sedimentary, and metamorphic. They are constantly changing. Rocks change shape and composition in a variety of ways.
Processes that change rock:* Weathering and Erosion – Weathering is the process which breaks rocks into smaller bits. Erosion is the removal and transport of material by wind, water, or ice.* Deposition – The process by which material is dropped or settles; makes layers that lead to formation of sedimentary rock
* Heat and Pressure - Earth movements can push all types of rock deeper into the Earth. These rocks are then subjected to massive temperatures and pressures causing the crystalline structure and texture to change. Yields metamorphic rocks.
* Cooling – Leads to the formation of igneous rocks that contain minerals randomly arranged in crystals. The size of the crystals tells you whether the rock cooled slowly or quickly Remember: Big crystals = cooled slowly underground = IntrusiveSmall crystals = cooled quickly after a volcanic eruption = Extrusive
It should be noted that the rock cycle is a model used by scientists to describe rocks’ changes on the Earth. Rocks rarely undergo the complete process shown in the traditional diagrams. Sedimentary rocks can become igneous rocks, and metamorphic rocks can become sedimentary rocks. It can take billions of years for changes to occur!
Credits:http://www.moorlandschool.co.uk/earth/rockcycle.htmHolt Science & Technology Earth Science. Texas: Holt, Rinehart and Winston, 2001.http://library.thinkquest.org/J002289/