CHAPTER 6 VOCABULARY TERMS DEFINED rock – the material that makes up the solid part of the Earth igneous – derived from the Latin term which means “from fire” and forms rock when magma or lava cools
and solidifies magma – molten rock located beneath Earth’s surface lava – molten rock located on top of Earth’s surface sediment – rocks, mineral crystals and organic matter that have been broken into fragments metamorphic – “changed form” chemical stability – the measure of the tendency of a chemical compound to maintain its original chemical
composition rather than break down to form a different chemical joints – evenly spaced zones of weakness generally found in massive igneous rock structures crystalline – made of crystals; generally found in most igneous rocks partial melting – the process by which different minerals in rock melt at different temperatures fractional crystallization – the crystallization and removal of different minerals from cooling magma coarse-grained texture – igneous rocks that are composed of large mineral grains fine-grained texture – igneous rocks that are composed of small crystals poryphyritic texture – igneous rock that has mixture of large and small crystals glassy – highly viscous magma that cools quickly and contains a very small percentage of dissolved gases vesicles – a rapid cooling of magma with a large percentage of dissolved gases that produces a rock full of holes vesicular texture – a texture of rock that contains vesicles ferromagnesian minerals – an igneous rock that has low concentration of silica and higher concentration of
iron and magnesium; results in a dark-colored rock intrusions – igneous rock masses that form underground batholiths – the largest of all intrusions that spread over 100 km
2 stock – similar to batholiths, but cover areas less than 100 km 2 laccolith – an intrusion that pushes overlying rock layers into a dome sill – magma flows between layers of rock and hardens dike – an intrusion that cuts through rock layers by following existing vertical fractures or creating new ones extrusions – igneous rock structures that forms on Earth’s surface volcano – a vent through which magma, gases and/or volcanic ash is expelled lava flow – flat masses of igneous rock on Earth’s surface tuff – volcanic ash deposits that form when a volcano releases ash and other solid particles during and eruption evaporates – minerals that are left behind when water evaporates from a solution conglomerate – clastic sedimentary rock that is composed of rounded fragments that range in size from fine
mud to boulders breccia – fragments that are angular and have sharp corners that make up clastic sedimentary rock sandstone – clastic sedimentary rock that is composed of sand-sized grains shale – clastic sedimentary rock that is composed of clay-sized particles sorting – the tendency of currents of air or water to separate sediments according to size depositional environment – the setting in which sediment is deposited stratification – layering of sedimentary rock beds – stratified layers cross beds – slanting of layers in sedimentary rock that generally form in sand dunes or river beds graded bedding – occurs when different sizes and shapes of sediment settle to different levels reverse grading – the smallest grains are on the bottom and the largest grains are on top; generally occurs
during mud flows ripple marks – features that are caused by the action of wind or water on sand fossils – the remains or traces of ancient plants or animals concretions – lumps of rock that have a composition that is different from that of the main rock body; form
when minerals precipitate from fluids and build up around a nucleus geode – minerals that crystallize inside the cavities to form a special type of rock

gneiss – metamorphosed rock that has bands of light and dark minerals rock cycle – the series of processes in which rock forms, changes from one type to another, is destroyed and
forms again by geologic processes
Bowen’s reaction series
– the simplified pattern that illustrates the order in which minerals crystallize from
cooling magma according to their chemical composition and melting point igneous rock – rock that forms when magma cools and solidifies intrusive igneous rock – rock formed from the cooling and solidification of magma beneath Earth’s surface extrusive igneous rock – rock that forms from the cooling and solidification of lava at Earth’s surface felsic – describes magma or igneous rock that is rich in feldspars and silica and that is generally light in color mafic – describes magma or igneous rock that is rich in magnesium and iron and that is generally dark in color compaction – the process in which the volume and porosity of a sediment is decreased by the weight of
overlying sediments as a result of burial beneath other sediments cementation – the process in which minerals precipitate into pore spaces between sediments grains and bind
sediments together to form rock chemical sedimentary rock – sedimentary rock that forms when minerals precipitate from a solution or settle
from a suspension organic sedimentary rock – sedimentary rock that forms from the remains of plants or animals clastic sedimentary rock – sedimentary rock that forms when fragments of preexisting rocks are compacted
or cemented together metamorphism – the process in which one type of rock changes into metamorphic rock because of chemical
processes or changes in temperature and pressure contact metamorphism – a change in the texture, structure or chemical composition of a rock due to contact
with magma regional metamorphism – a change in the texture, structure or chemical composition of a rock due to changes
in temperature and pressure over a large are, generally as a result of tectonic forces foliation – the metamorphic rock texture in which mineral grains are arranged in planes or bands nonfoliated – the metamorphic rock texture in which mineral grains are not arranged in planes or bands