Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download THE ROCK CYCLE WHAT YOU LEARN To distinguish between
Transcript
THE ROCK CYCLE WHAT YOU LEARN To distinguish between minerals and rocks How rocks are classified How rocks are constantly recycled providing raw materials for other rocks HOW ROCKS RECYCLE The rock cycle is a general model that describes how various geological processes create, modify, and influence rocks. the origin of all rocks can be ultimately traced back to the solidification of molten magma. Magma consists of a partially melted mixture of elements and compounds commonly found in rocks. Magma exists just beneath the solid crust of the Earth in an interior zone known as the mantle. (Figure 1) All rock types can be physically and chemically decomposed by a variety of surface processes collectively known as weathering. The debris that is created by weathering is often transported through the landscape by erosional processes via streams, glaciers, wind, and gravity. When this debris is deposited as a permanent sediment, the processes of burial, compression, and chemical alteration over long periods of time produce sedimentary rocks A number of geologic processes, like tectonic folding and faulting, can exert heat and pressure on both igneous and sedimentary rocks causing them to be altered physically or chemically. Rocks modified in this way are termed metamorphic rocks Composition of the Crust The earth’s crust is composed of rocks Rocks are composed of minerals What is a mineral? A mineral is: A naturally occurring inorganic substance With a definite chemical composition and Characteristic atomic structure Rock Classification Igneous Rocks form from the cooling and crystallization of magma. Sedimentary Rocks form from lithification of sediments from other rocks. Metamorphic Rocks form from recrystallization of other rocks due to heat, pressure, and chemical alteration. IGNEOUS ROCKS Igneous Rocks Are Subdivided Into Two Classes 1. Volcanic (Extrusive) Igneous Rocks Volcanic extrusive igneous rocks form at the earth's surface as lava cools. Basalt Basalt is the most widespread volcanic rock. It is a dark, fine-grained rock. Basalt is the rock of the sea floor. 2. Plutonic (or Intrusive) Igneous Rocks Plutonic igneous rocks form deep underground where magma cools slowly Plutonic rocks have a coarse crystalline texture. Granite Granite is the most widespread of plutonic igneous rocks. It underlies much of the continental crust. SEDIMENTARY ROCKS Most sedimentary rocks are formed of layers of materials that have washed into lakes, rivers, and the ocean. Sedimentary Rocks Form Strata Sometimes these layers are tilted by earth movements. Sedimentary Rocks Contain Fossils Subclasses of Sedimentary Rocks 1. 2. 3. Clastic: rocks form from bits and pieces of other rocks. Chemical: rocks consist of minerals deposited from a solution. Organic: rocks consist of organic matter such as plants and animal remains. How do sediments turn into hard rock? Lithification Processes: Compaction Cementation Crystallization Organically-Formed Sedimentary Rocks Organically-formed sedimentary rocks form from the remains of plants and animals. Fossil limestone Coal METAMORPHIC ROCKS Metamorphic rocks are rocks that have been changed in form due to heat, pressure, and chemical alteration. FOLIATED NONFOLIATED Slate Marble Schist Quartzite Gneiss SUMMARY Igneous Rocks Volcanic (Extrusive) Igneous Plutonic (Intrusive) Igneous Sedimentary Clastic Chemical Organic Metamorphic Foliated Nonfoliated The Rock Cycle shows how rocks of any rock class can be recycled into rocks of any other rock class. of the rock types described above can be returned to the Earth's interior by tectonic forces at areas known as subduction zones. Once in the Earth's interior, extreme pressures and temperatures melt the rock back into magma to begin the rock cycle again.
