Chapter 2 Rocks: Mineral Mixtures

Section 1 The Rock Cycle

rock always changing a naturally occurring solid mixture of one or more minerals and/or organic matter

rock cycle the series of processes in which a rock forms, changes from one type to another, is destroyed and forms again by geological processes

weathering the process in which water, wind, ice and heat break down rock breaks rock down into fragments (which sedimentary rock is made)

erosion the process by which wind, water, ice or gravity transports soil and sediment from one location to another

deposition the process in which sediment is moved by erosion and comes to rest in a new location sediment is deposited in bodies of water and other low-lying areas sediment may be pressed and cemented together by minerals dissolved in water to form sedimentary rock

uplift movement within the Earth that causes rocks inside the Earth to be moved to the Earth’s surface when rock is uplifted to surface weathering, erosion and deposition begin

magma the hot liquid that forms when rock partially or completely melts 3 ways magma can form: 1) when rock is heated 2) pressure is released 3) when rock changes composition  freezes between 700º and 1250º C

composition the chemical makeup of a rock describes either the minerals or other materials in the rock limestone = 95% calcite and 5% aragonite  granite = 55% feldspar, 35% quartz and 10% biotite mica

texture the quality of a rock that is based on the sizes, shapes and positions of the rock’s grains examples = fine grained, medium grained or coarse grained texture  can provide clues as to how and where the rock formed

SECTION 2 IGNEOUS ROCKS

igneous rock forms when hot, liquid rock (magma) cools and solidifies are located above and below the surface

felsic rocks igneous rocks that are light in color and rich in elements such as aluminum, potassium, silicon and sodium examples = granite and rhyolite

mafic rocks igneous rocks that are dark in color and rich in calcium, iron and magnesium (poor in silicon) examples = gabbro and basalt

intrusive igneous rock rock formed from the cooling and solidification of magma beneath the Earth’s surface usually have a coarse grained texture  cools very slowly and forms minerals that are large, visible crystals  common intrusive shapes = plutons, batholiths, stocks, dikes and sills

intrusive igneous rock

extrusive igneous rock rock that forms as a result of volcanic activity at or near the Earth’s surface also called lava rocks common around volcanoes cools quickly and contain very small or no crystals

extrusive igneous rock

lava plateau when a large amount of lava flows out of fissures onto land and covers a large area pre-existing landforms are often buried by these lava flows

Section 3 SEDIMENTARY ROCK

sandstone when sand grains are compacted or compressed and then cemented together one of the many types of sedimentary rock

sedimentary rock through erosion rock and mineral fragments are moved from one place to another and eventually deposit in layers. As new layers arrive, old layers are compacted & cemented together binding minerals and rock together form at or near the Earth’s surface  forms without heat and pressure  most noticeable feature is the layers/strata fossils can only be found in sedimentary rock

strata horizontal layers of rock

clastic sedimentary rock forms when rock or mineral fragments (called clasts) are cemented together by minerals such as calcite or quartz classified according to the size of fragments: fine, medium and coarse grained

chemical sedimentary rock forms from solutions of dissolved minerals and water when minerals crystallize out of a solution, such as sea water to become rock example = halite

organic sedimentary rock forms from the remains or fossils of once living plants and animals example = many limestone made of skeletons of tiny organisms (coral) example = coal

stratification the process in which sedimentary rocks are arranged in layers differ from one another depending on the kind, size and color of their sediment

Section 4 Metamorphic Rock

metamorphic rock rocks in which the structure, texture or composition of the rock have changed all metamorphic rock has 1 of 2 textures: foliated or nonfoliated

metamorphism when rocks change shape all three types of rock can be changed by heat, pressure or a combination of both

contact metamorphism when rock is heated by nearby magma occurs near igneous intrusions

regional metamorphism when pressure builds up in rock that is buried deep below other rock formations or when large pieces of the Earth’s crust collide with each other causes rock to become deformed and chemically change  occurs over thousands of cubic kilometers deep within Earth’s crust

regional metamorphism

foliated the texture of metamorphic rock in which the mineral grains are arranged in planes or bands usually contain aligned grains or flat minerals such as mica or chlorite example= shale slate phyllite schist gneiss

foliated

nonfoliated the texture of metamorphic rock in which the minerals are not arranged in planes or bands commonly made of one or only a few minerals  Example= quartz sandstone quartzite or limestone marble

deformation a change in the shape of a rock caused by a force placed on it folds or bends in rock