Term
click below
click below
Term
Normal Size Small Size show me how
GEO 101 Exam II
vocab words for second geo exam
Term | Definition |
---|---|
viscosity | a measure of resistance to flow |
cinder cone | - steep, conical hills with a prominent crater at the top - smallest, simplest type of volcano - also know as pyroclastic cones - erupts explosively |
shield volcano | - broad-domed volcano with gently sloping sides - resembles a shield on its side - effusive eruption style (basaltic lava) |
stratovolcano/composite volcano | - steep sides - highly viscous lava (builds up around the vent, forming the steep sides) - explosive eruption style |
effusive eruption | - dominated by the outpouring of lava onto the ground, as opposed to large, explosive eruption |
dike | - a discordant intrusive sheet - igneous, cuts vertically across pre-existing rock |
sill | - similar to a dike - concordant intrusive sheet (meaning that it does not cut across pre-existing rock) - forms parallel to existing rock |
pluton | - a body of intrusive igneous rock (called plutonic rock) that is crystalized from magma cooling slowly deep beneath the earth |
batholith | - a very large igneous intrusion extending deep into the earth's crust |
columnar jointing | - consists of sets of regularly spaced parallel fractures -- joints -- that intersect in a roughly prismatic pattern |
physical weathering | - occurs when physical processes effect the rock -- such as changes in temp, or erosion due to wind or rain - never changes the chemical composition of the rock |
differential weathering | - the idea that weathering is not uniform - rocks, or parts of rocks, can be exposed to the same environment and experience different weathering |
carbonic acid | - an acid composed of carbon and oxygen (H2CO3) - major contributor to chemical weathering, causes rocks to dissolve - formation of stalagmites |
dissolution | - process by which a solute dissolves into a solution - process of dissolving |
oxidation | - process by which a chemical compound changes due to the addition of oxygen - rust etc |
hydrolysis | - any chemical process in which water breaks one or more chemical bonds |
jointing | - a brittle-fracture surface in rocks along which little/no displacement has occurred - occurs due to tensile stress, such as the stretching of layers |
exfoliation | -a form of mechanical weathering in which curved plates of rock are stripped from rock below. -This results in exfoliation domes (dome-like hills and rounded boulders) |
clastic sedimentary rock | - made up of pieces (clasts) from pre-existing rocks |
(bio)chemical sedimentary rock | - formed from the shells/bodies of marine organisms, or from organic matter like plant remains - limestone, coal, etc |
evaporite | - rocks composed mostly of minerals produced by evaporation of saline solutions |
conglomerate | -a sedimentary rock made of rounded pebbles and sand that is usually held together (cemented) by silica, calcite or iron oxide |
breccia | - a sedimentary rock composed of large, angular clasts, which are cemented together - similar to conglomerate, except with angular rather than rounded clasts |
arkose | - a type of sandstone containing at least 25% feldspar |
siltstone | - a clastic sedimentary rock composed mostly of silt - very fine-grained, uniform in color |
shale | - a soft, brittle, fine-grained, and easily eroded sedimentary rock - formed from mineral-rich silt, or mud, that was deposited in an aquatic environment, buried by other sediment, and compacted and cemented into hard rock |
limestone | - biochemical sedimentary rock - composed primarily of calcium carbonate (calcite) |
alluvial fan | - a triangle-shaped deposit of gravel, sand, and even smaller pieces of sediment, such as silt. This sediment is called alluvium. - - Alluvial fans are usually created as flowing water interacts with mountains, hills, or the steep walls of canyons |
delta | - a type of wetland that forms where rivers empty their water and sediment into another body of water (such as an ocean, lake, or another river) |
mudcrack | - form in very fine clay material that has dried out. - As the moisture is removed, the surface will split into cracks that extend a short way down into the mud. - These cracks form polygons on the surface of the mud. |
ripple marks | - sedimentary structures indicating agitation by water (either currents or waves) or by wind |
marine transgression | - a geologic event during which sea level rises relative to the land and the shoreline moves toward higher ground, which results in flooding |
marine regression | - a geological process occurring when areas of submerged seafloor are exposed above the sea level - the opposite of a marine transgression |
foliation | - repetitive layering in metamorphic rocks |
slate | - a fine-grained, foliated metamorphic rock that is created by the alteration of shale or mudstone by low-grade regional metamorphism |
schist | - course-grained metamorphic rock - consists of layers of different minerals and can be split into thin, irregular plates - shiny - low/middle grade -shale can be a protolith |
gneiss | - high-grade metamorphic rock with clear foliation, representing alternating layers composed of different minerals - granite, or some sedimentary rocks, can be protoliths |
quartzite | - a hard, non-foliated metamorphic rock - originally pure quartz sandstone |
marble | - a metamorphic rock that forms when limestone is subjected to the heat and pressure of metamorphism - foliated |
metamorphic grade | - how metamorphized a rock is; a way of describing the relative temperature and pressure a rock is subject to |
uniformitarianism | - the theory that changes in the earth's crust during geological history have resulted from the action of continuous and uniform processes - things have not changed; the same natural laws/processes we have now applied in geologic history |
principle of superposition | - a layer/rock that is below another is the oldest |
principle of horizontality | - all rock layers form horizontally, though they may later be deformed |
principle of inclusions | - any inclusion (such as a xenolith) within a rock must be older than the rock itself |
unconformity | - a buried erosional or non-depositional surface separating two rock masses or strata of different ages, indicating that sediment deposition was not continuous - where two layers meet, and there is missing time due to erosion/non-deposition |
angular unconformity | - formed when originally horizontal rocks are deformed, uplifted, and eroded - where layers of rock have been tilted, and now non-tilted/flat rocks form on top of them |
nonconformity | - unconformities that separate igneous or metamorphic rocks from overlying sedimentary rocks - They indicate that a long period of erosion occurred prior to deposition of the sediments (enough to bring rocks from deep below the earth to the surface) |
disconformity | - A geologic surface that separates younger strata from older strata and represents a time of nondeposition, possibly combined with erosion |
principle of baked contacts | - states that the heat of an intrusion will bake (metamorphose) the rocks in close proximity to the intrusion - Hence the presence of a baked contact indicates the intrusion is younger than the rocks around it |
numeric age dating | - the process of determining the exact age of a rock |
radioactive isotope | - atoms that contain an unstable combination of neutrons and protons, or excess energy in their nucleus |
daughter isotope | - the more stable form of the parent isotope |
half-life | - the time it takes for the radioactivity of an isotope to drop to half of its current value |
epicenter | - the point directly above the focus on a map |
earthquake focus | - the point underground where rocks first break, causing an earthquake - directly below the epicenter |
elastic deformation | - deformation in which the material will return to it's original state after stress is removed |
elastic rebound theory | As rocks on opposite sides of a fault are subjected to force, they gain energy + slowly deform until their internal strength is exceeded. Then, a sudden movement occurs along the fault, releasing the energy, and the rocks return to their original shape |
body seismic waves | - waves that can travel through Earth's inner layers, as opposed to only along the surface |
surface seismic waves | - waves that only travel along Earth's surface |
P-wave | - body seismic wave, can travel through liquid - moves from horizontally - fastest seismic wave |
S-wave | - body seismic wave, cannot travel through liquid - moves in an up-and-down motion, like a sine wave |
wave refraction | - the bending of waves as they pass from one material to another - ex: when waves move from solid outer mantle to liquid inner mantle |
shadow zone | - the area of the earth from angular distances of 104 to 140 degrees that, for a given earthquake, that does not receive any direct P waves |
normal fault | - a fault where the hanging wall block moves down relative to the footwall |
reverse fault | - a fault where the hanging wall block moves up relative to the footwall |
strike-slip fault | - a fault on which the two blocks slide past one another |
anticline | - a ridge-shaped fold of stratified rock in which the strata slope downward from the crest - frown-shape due to deformation (compressional stress) - occurs with synclines |
syncline | - a trough-shaped fold due to compressional stress/deformation - smiley face :) - occurs with anticlines |