Physical Changes In Igneous And Sedimentary Rocks example essay topic

The rock cycle has only three types of rocks, igneous rock, sedimentary rock and metamorphic rock. Each of these rocks can form at the expense of the other. Igneous rocks are created when molten material such as magma (within the earth) or lava (on the surface) cools and hardens. The hot material crystallizes into different materials.

The properties and sizes of the various crystals depend on the magmas composition and its rate of cooling. Examples of Igneous rock are Granite, Obsidian, Basalt, Pumice, Andesite, Diorite and Rhyolite. Sedimentary rocks are made up of sediments eroded from igneous rock, metaphoric rock, other sedimentary rocks, and even the remains of dead plants and animals. These materials are deposited in layers, or strata, and then are squeezed and compressed into rock. Most fossils are found in sedimentary rocks.

Examples of these are Sandstone, Shale, Conglomerate, Limestone, Chert, Coal and Gypsum. Metamorphic rocks are produced when sedimentary or heat and / or pressure transform igneous rocks. The word "metamorphic" comes from the Greek language, which means, "to change form". Examples of these are Marble, Slate, Quartzite, Schist and Gneiss. The rock cycle is somewhat like a gigantic machine, and it never stops. The rock cycle works begins when liquid molten rock material solidifies either at or below the surface of the earth to form igneous rocks.

Uplifting occurs forming mountains made of rock. The exposure of weathering and erosion at the earth's surface breaks them down into smaller grains producing soil. The grains (soil) transported by wind, water and gravity eventually deposited as sediments. This process is referred to as erosion.

The sediments are deposited in layers and become compacted and cemented forming sedimentary rocks. Variation in temperature, pressure and / or the chemistry of the rock can cause chemical and / or physical changes in igneous and sedimentary rocks to form metamorphic rocks. When exposed to higher temperatures, metamorphic rocks may be partially melted resulting in the creation once again of igneous rocks starting the cycle all over again. If someone looks at the rock cycle in terms of plate tectonics, igneous rocks form on the sea floor as spreading ridges.

As the rocks cool, and more magma comes from below, the plate is forced away from the spreading ridge, and requires a sediment cover. As the oceanic plate travels deeper, high temperature conditions cause partial melting of the crystal slab. When this happens the surrounding country rock is metamorphosed at high temperature conditions by the contact. The molten material is either driven to the surface as volcanic eruptions, or crystallizes to form plutonic igneous rock. This is how the continuous rock cycle works..