Sedimentary Vocabulary

Updated 2007-04-06 08:19


Geology 101.

Sedimentary Vocab

Vocab WordDefinition
arkosemixture of quartz and feldspar grains that has been lithified
basementOlder igneous and metamorphic rocks making up the Earth's crust beneath sedimentary cover
bedLayer of sedimentary rock with recognizable top and bottom
biochemical sedimentary rocksSedimentary rock formed from material (such as shells) produced by living organisms.
brecciaCoarse sedimentary rock consisting of angular fragments; or rock broken into angular fragments by faulting
caliche (calcrete)A solid mass created where calcite cements the soil together
cementMineral material that precipitates from water and fills the spaces between grains, holding the grains together
chemical sedimentary rocksSedimentary rocks made up of minerals that precipitate directly from water solution
chemical weatheringProcess in which chemical reactions alter or destroy minerals when rock comes in contact with water solutions and/or air
chertSedimentary rock composed of very fine-grained silica (cryptocrystalline quartz)
clastic sedimentary rocksSedimentary rock consisting of cemented-together detritus derived from the weathering of preexisting rock.
coalblack combustible organic rock, composed of over 50% carbon
compactionPhase of lithification in which the pressure of the overburden on the buried rock squeezes out water and air that was trapped between clasts, and the clasts press tightly together
conglomerateVery coarse-grained sedimentary rock consisting of rounded clasts
coverThin layer of sediment and sedimentary rock over older igneous and metamorphic rocks
cross beads
depositionProcess by which sediment settles out of a transporting medium
detritusThe chunks and smaller grains of rock broken off outcrops by physical weathering
diamictiterock formed from debris flows or in glacial settings where where ice deposits clasts of all sizes
dolostonelike limestone, but contains mineral dolomite
dunesPile of sand generally formed by deposition from the wind
erosionGrinding away and removal of Earth's surface materials by moving water, air, or ice.
evaporitessalt deposit formed as a result of evaporation
exfoliationProcess by which an outcrop rock splits apart into onion like sheets along joints that lie parallel to the ground surface
fossilsRemnant or trace of an ancient living organism that has been preserved in rock or sediment
frost wedgingProcess in which water trapped in a joint freezes, forces the joint open, and may cause the joint to grow.
graded bed
horizonsDistinct zones formed by different soil processes at different depths
jointsNaturally formed cracks in rocks
laterite soilSoild formed over iron-rich rock in a tropical environment, consisting primarily of a dark-red mass of insoluble iron and/or aluminum oxide
limestoneSedimentary rock composed of calcite
lithificationTransformation of loose sediment into solid rock through compaction and cementation
mud cracks
mudstonevery fine grained sedimentary rock that will not easily split into sheets
organic sedimentary rocksSedimentary rock (such as coal) formed from carbon rich relicts of organisms
pedalfer soilTemperature-climate soil characterized by well defined soil horizons and a well defined A-horizon
pedocal soilThin soil formed in arid climates. It contains very little organic matter but significant precipitated calcite
physical (mechanical) weatheringProcess in which intact rock breaks into smaller grains or chunks
regolithAny kind of unconsolidated debris that covers bedrock
regressionSeaward migration of shoreline caused by a lowering of the sea level
ripples (ripple marks)small elongated ridges that form on beds
root wedging
salt wedgingProcess in arid climates by which dissolved salt in groundwater crustallizes and grows in open pore spaces in rocks and pushes apart the surrounding grains
sandstoneCoarse-grained sedimentary rock consisting almost entirely of quartz
saprolitelayer of rotten rock created by chemical weathering in warm, wet climates
scour marks
sedimentAccumulation of loose mineral grains, such as BOULDERS, PEBBLES, SAND, SILT, AND CLAY (BPSSC)
sedimentary basinDepression, created as a consequence of subsidence, that fills with sediment
sedimentary environment
sedimentary rockRock that forms either by cementing together of fragments broken off preexisting rock or by the precipitation of mineral crystals out of water solutions at or near the earth's surface
shaleVery fine-grained sedimentary rock that breaks into thin sheets
siltstonefine-grained sedimentary rock generally composed of very small quartz grains
soilsediment that has undergone changes at the surface of the earth, including reaction with rainwater and the addition organic material.
soil erosionremoval of soil by wind and runoff
soil profilevertical sequence of distinct zones of soil
sorting1. Range of clast sizes in a collection of sediment; 2. degree to which sediment has been separated by flowing currents into different-size fractions
strataseveral beds of stratified sedimentary rock
stratigraphic formationA recognizable layer of a specific sedimentary rock type or set of rock types, deposited during a certain time interval that can be traced over a broad region
subsidenceVertical sinking of the Earth's surface in a region, relative to a reference plane.
talusSloping apron of fallen rock along the base of a cliff
transgressionInland migration of shoreline resulting in a rise of sea level
travertineRock composed of crystalline calcium carbonate (calcite and/or aragonite) formed by chemical precipitation out of groundwater that has seeped out at the ground surface or on the walls of caves.
turbiditeGraded bed of sediment built up at the base of a submarine slope and deposited by turbidity currents
wackerock that forms from the deposits of submarine avalanches
weatheringProcess that break up and corrode solid rock, eventually transforming it into sediment
zone of accumulation1. Layer of regolith in which new minerals precipitate out of water passing through, thus leaving behind a load of fine clay 2. the area of a glacier in which snow fall adds to the glacier
zone of leachingLayer of regolith in which water dissolves ions and picks up very fine clay; these materials are then carried downward by infiltrating water.

Volcano Vocab

a'a'Lava flow with rubbly surface
active volcanoesvolcano that has erupted in the last few centuries and will likely erupt again
aerosolsTiny solid particles or liquid droplets that remain suspended in the atmosphere for a long time
calderaLarge, circular depression with steep walls and a fairly flat floor, formed after an eruption as the center of the volcano collapses into the drained magma chamber below
cinder conesubaerial volcano consisting of a cone shaped pile of tephra whose slop approaches the angle of repose for tephra
columnar jointingtype of fracturing that yields roughly hexagonal columns of basalt; columnar joints form when a dike, sill, or lava flow cools
crater1. circular depression at the top of a volcanic mound 2. depression formed by the impact of a meteorite
dormant volcanoesvolcano that has not erupted for hundred to thousands of years but does have the potential to erupt again in the future
effusive eruptionEruption that yields mostly lava, not ash.
explosive (pyroclastic) eruptionviolent volcanic eruptions that produce clouds and avalanches of pyroclastic debris
extinct volcanoesVolcano that will never erupt again
fissureConduit in magma chamber the shape of a long crack through which magma rises and erupts through the surface
flood basaltVast sheets that spread from a volcanic vent over an extensive surface of land; they may form where a rift develops above a continental hot spot, and where lava is particularly hot and has low viscosity
ignimbriteRock formed when deposits of pyroclastic flows solidify
laharThick slurry formed when volcanic ash and debris mix with water, either in rivers or from rain or melting snow and ice on the side of a volcano
lapillimarble to plum size fragments of pyroclastic debris
lava domedome like mass of rhyolitic lave that accumulates above the eruption vent
lava flowsheets or mounds of lava that flow onto the ground surface or sea floor in molten form and then solidify
lava tubeEmpty space left when lava tunnel drains; this happs when the surface of a lava flow solidifies while the inner part of the flow continues to stream downslope
magma chamberspace below ground filled with magma
marebroad darker areas on moons surface which consist of flood basalts that erupted over 3 billion years ago and spread out across the moon's lowlands
pahoehoeLava flow with a surface texture of smooth, glassy, rope like ridges
phreatomagmatic eruptionexplosive eruption that occurs when water enters the magma chamber and turns into steam
pyroclastic debrisfragmented material that sprayed out of a volcano and landed on the ground or sea floor in solid form.
pyroclastic flowfast moving avalanche that occurs wen hot volcanic ash and debris mix with air and flow down the side of a hot volcano
recurrence intervalaverage time between successive geological events
Ring of Fire
shield volcanoSubaerial volcano with a broad, gentle dome formed either from low-visocsity basaltic lava or from large pyroclastic sheets
stratovolcano (composite volcano)large , cone shaped subaerialconsisting of alternating layers of lava and tephra
tephraUnconsolidated accumulations of pyroclastic grains
tuffpyroclastic igneous rock composed of volcanic ash and pumice, formed when accumulations of the debris cement together
vesiclesopen holes in igneous rock formed by the preservation of bubbles in magma as the magma cools into solid rock
volcanic ashtiny gas shards formed when a fine spray of exploded lava freezes instantly upon contact with the atmosphere
volcanic danger assessment mapmap delineating areas that lie in the path of potential lava flows, lahars, debris flows, or pyroclastic flows of an active volcano
volcano1. Vent from which melt from inside the earth spews out ontothe plant's surface; 2. A mountain formed by the accumulation of extrusive volcanic rock.