Geology Notes Part 1 The Rock Cycle What

Geology Notes Part 1 The Rock Cycle

What is a rock? • A rock is a mixture of such minerals, rock fragments, volcanic glass, organic matter, or other natural materials.

There is a hierarchy to the Atoms make up elements of Geology Elements combine to form the natural compounds. . Natural compounds and elements combine to form minerals. Minerals make up rocks. Rocks make up the Earth.

How are rocks classified? • first they are classified into three groups based on the way in the rocks were formed – Igneous, Sedimentary, and Metamorphic • then they are divided further based on their composition and texture

What are igneous rocks? • a rock formed by the cooling and solidification of magma or lava

What are some igneous rocks? • granite, basalt, obsidian, pumice, gabbro, rhyolite • they depend on the composition of the magma and the amount of time it takes to cool PUMICE

What determines the size of the crystals in igneous rocks? • How fast it cools; the slower it cools, the larger the crystals that form Granite - Cool slowly; thousands to millions of years; course grained Rhyolite - Cool quick; days to weeks; fine grain or microscopic grains Obsidian - Cool VERY quick; hours to days; no crystals form

What is the difference between intrusive and extrusive rocks? • Intrusive are formed when magma cools slowly within the Earth’s crust • Extrusive form when magma cools fast at the surface Extrusive rock forms here

Geology Notes Part 2 The Rock Cycle

What are metamorphic rocks? • Metamorphic rocks are formed when other kinds of rocks are changed by great heat and pressure inside the earth. • The word "metamorphic" means changed. • Think of metamorphic rocks as recycled rocks.

What are some metamorphic rocks? • Marble, quarttzite, slate, schist, gneiss • Limestone can be changed to marble, sandstone can be changed into quartzite, and shale can be changed to slate

What is the difference between foliated and nonfoliated metamorphic rocks? • Foliation is a broad term referring to the alignment of sheet-like minerals. (Slate, Gneiss) • Non-foliated or granular metamorphic rocks are those which are composed of equidimensional grains such as quartz or calcite. There is no preferred orientation. (Marble, Quartzite

What is the difference between contact and regional metamorphism? • Rocks that are in contact with hot magma or lava often become metamorphosed. This is called contact metamorphism. • Sometimes rocks are metamorphosed over large areas that are the size of many states or even several countries.

Explain how the texture of metamorphic rock can indicate whether it has experienced regional or contact metamorphism. • Foliation occurs when a strong compressive force is applied from one direction. • Rocks that were subjected to uniform pressure from all sides, or those which lack minerals with distinctive growth habits, will not be foliated.

Geology Notes Part 3 The Rock Cycle

What are sedimentary rocks? • Sedimentary rocks are formed at the surface of the Earth, either in water or on land. • They are layered accumulations of sediments: fragments of rocks, minerals, or animal or plant material.

What are some sedimentary rocks? • sandstone, limestone, shale, and conglomerate

How are sedimentary rocks categorized? • Like igneous and metamorphic rocks, sedimentary rocks are classified by their composition and by the manner in which they formed. • The three categories are: – Clastic - are made up of pieces (clasts) of pre-existing rocks that becomes compacted and cemented. – Chemical - are formed by chemical precipitation, when water traveling through rock dissolves some of the minerals, eventually the minerals are redeposited when the water evaporates away. – Biologic/Organic - form from once-living organisms. They may form from accumulated carbon-rich plant material or from deposits of animal shells.

Explain how the size and shape of grains in a sedimentary rock indicate the environment of formation (including climate) and deposition. • The grain size depends on the energy of the environment in which the sediment was deposited. • The general shape of the grains will tell you about the nature of the transporting medium. • For example, a vigorous river transports much larger grains than a gentle current in a lake, so the size of the grains gives an indication of the strength of the currents that could have transported and deposited the grains. Animation http: //www. classzone. com/books/earth_science/terc/content/visualizations/es 060 4/es 0604 page 01. cfm? chapter_no=visualization

Geology Notes Part 4 The Rock Cycle

What are the processes that change one kind of rock into another? • When sediments from any rock are compacted or cemented, the sediment becomes a sedimentary rock • a sedimentary rock can change by heat and pressure to form a metamorphic rock • any rock can be melted and later cool to form an igneous rock.