| 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 |
