Geology Test 2
Geology Test 2
Terms
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- Geode
- Similar to a nodule_ but hollow and lined with crystals
- Sedimentary rocks
- Rocks formed when sediment is turned into stone
- Chemical Weathering
- Rock chemically changes into minerals that are more stable on Earth's surface
- Mechanical (Physical) Weathering
- Breaking of rock into smaller pieces by natural forces without changing its composition
- Cap rock
- Impermeable rock_ such as shale or clay that keeps oil and gas from escaping the trap.
- Schist
- Visibly crystalline (sparkles). Layers typically uneven (wavy). Uneven rock cleavage. Mostly platy (flat_ flat-like) minerals_ such as mica.
- Anthracite
- Hard coal. Highest grade. Least volatiles. Most carbon. Highest energy yield. Forms when lower grade coal is heated and compressed during formation of mountains. Rarest type.
- Transported Soil
- Sediments deposited on top of the bedrock by water_ wind_ or ice. Soil formed from this is called this kind of soil.
- Chert
- Made of microcrystalline quartz. Very fine-grained. Hard_ dense and durable. Breaks like glass to form a sharp edge. Sometimes bioclastic (fossiliferous). Typically occurs as nodules in carbonate rocks_ but can also be in layers. Forms in the ocean_ shallow to deep sea.
- Root Wedging
- Caused by the force generated by plant roots growing in cracks
- Ripple Marks
- Wave-like ripples caused by waves_ currents_ or wind disturbing sediment. Associated with water which has been agitated by waves or currents.
- Weathered parent material (C-horizon)
- Rock or sediment from which the mineral part of the soil comes_ i.e. regolith.
- Soil
- A mix of mineral matter from weathering_ and organic matter from biological activity. Regolith_ Humus_ Water_ and Air are its four major ingredients. Formed by a combination of inorganic weathering and biological activity
- Formation of coal
- Plant debris is deposited in stagnant (low oxygen) water, i.e. a swamp or bog, where it can't completely decay. This forms organic peat (a low grade fuel). Next, the peat is deeply buried under more sediments, which heats and compresses it. This drives off volatiles (water, CO2, and methane), and concentrates carbon to form this
- Mud Cracks
- A network of cracks dividing the surface into polygons. Formed when sediment dries out_ shrinks_ and cracks open. Associated with desert basins and shallow lakes and river flood plains.
- Subsoil (B-horizon)
- Zone of mineral accumulation. Shades of red_ orange_ or brown due to iron oxides. Mostly clay_ quartz_ and some soluble minerals removed from the topsoil.
- Oxidation
- Reaction of a mineral with oxygen to form an oxide or hydroxide mineral
- Frost Wedging
- Caused by water freezing and expanding in its cracks. Conditions necessary for it are climates where the temperature often rises and falls above and below freezing
- Organic
- Made of hydrocarbons formed from plants
- Foliation (foliated texture)
- A preferred crystal alignment resulting in such traits as layering_ banding_ and rock cleavage. Caused by the effects of directed pressure (compression).
- Regional metamorphism
- Recrystallization of a vast volume of rock due to widespread heating and compression. Accompanies formation of mountain ranges at convergent plate boundaries. Heat and compression deform lithosphere_ recrystallizing some rock.
- Quartzite
- Visibly crystalline. Granular "sugary" look. Forms from sandstone.
- Lower Topsoil (A horizon)
- Mostly mineral matter + as much as 30% humus. Also dark colored. Most clay and soluble minerals (calcite and gypsum) have been removed by downward moving water.
- Crystalline
- Made of interlocking crystals
- Gneiss
- Visibly crystalline. Banded (separation of light and dark minerals). No rock cleavage. Mostly feldspar and quartz (light bands). Dark bands are ferromagnesium silicates.
- Compaction
- A reduction in volume due to the weight of overlying sediments squeezing out air and water. This alone isn't enough to transform rock_ except for shale (compacted mud)
- Hydrolysis
- Reaction of a mineral with water to form a hydrated mineral_ typically clay minerals
- Thermal
- some surrounding rock is "baked" by the magma_ recrystallizing it.
- Concretion
- Local concentration of the mineral cement
- Bioclastic
- Made of cemented shells_ etc.
- Humus
- Dark-colored organic matter. Formed by the decay of plants_ animals_ and animal wastes
- Biochemical
- Formed by organic precipitation (shells_ corals_ etc.) of dissolved salts
- Sediment
- Loose materials transported and deposited by erosion
- Erosion
- Wearing away and transportation of rock by natural agents
- Nodule
- Local concentration of a foreign mineral
- Slate
- Very fine-grained (microcrystalline). Closely spaced even layers. Very good rock cleavage. Mostly mica & quartz.
- Solution
- Dissolving away of rock by water, especially acidic water, to form ions (dissolved salts)
- Cross-Bedding
- A stack of sets of tilted strata in which the direction and angle of tilt can vary from set to set. Forms from migration of a slope on which sediment is deposited_ i.e. the downside of a dune_ or the downstream side of a sandbar.
- Rock cleavage
- Rock splits parallel to foliation_ and can be even or wavy. Not typical of banded rocks.
- Topsoil (O horizon)
- Almost entirely organic matter. Dark brown to black. Upper part is recognizable by organic debris (leaves_ twigs_ etc). Lower part is unrecognizable grains of decomposed_ humus-rich organics
- Lignite
- Brown coal. Low grade. Most volatiles. Lowest % carbon. Lowest energy yield.
- Bituminous
- Soft coal. Medium grade. Less volatiles. More carbon. Higher energy yield.
- Shale
- Very fine-grained. Thinly layered. Soft_ crumbly_ and easily weathered. Mostly tiny bits of clay and quartz. Most common sedimentary rock. Forms from mud deposited in nonturbulent conditions_ often deep water.
- Unloading (exfoliation or sheeting)
- Rocks break along parallel cracks to form layers. Caused by the expansion of rock as the weight of overlying rocks is removed by erosion
- Coal
- an organic textured rock formed from plant debris.
- Metamorphic rocks
- Rocks formed by recrystallization without melting due to heat and pressure deep underground. They form from igneous_ sedimentary_ and other metamorphic rocks.
- Nonfoliated texture
- A random crystal alignment that lacks layers_ bands_ or rock cleavage. Formed because either rock wasn't compressed_ or if it was_ it was made of minerals that don't show it.
- Regolith
- decomposed and disintegrated rock. It is the mineral part of soil
- Chemical
- Formed by inorganic precipitation of dissolved salts (ions in solution)
- Normal (horizontal) bedding
- horizontal layers deposited one atop another. Each layer = an episode of sediment deposition_ followed by a break during which sediment consolidates before more is laid on top of it.
- Chemically active fluids
- Brines (salty water) in the pores that act as a chemical catalyst. Greatly speeds up the process by making it easier for atoms to move from one mineral grain to another. They speed up the recrystallization process.
- Weathering
- Decomposition and disintegration of rock by natural agents
- Clastic
- Made of cemented and/or compressed particles
- Cementation
- Binding of particles by minerals deposited by water moving through pores
- Nodules, concretions, and geodes
- Mineral deposits embedded in rock
- Evaporites (rock salt and rock gypsum)
- Inorganic precipitation formed from hypersaline (highly salty) water. Form in hot_ dry climates where water is shallow and evaporation rates are high_ which concentrates salt. Usually form along sea coasts_ or in desert salt lakes.
- Fossils
- Evidence of prehistoric life_ such as bones_ teeth_ shells_ petrified wood_ and tracks.
- Detrital
- Materials from the land that consist of particles (gravel_ sand_ & mud)
- Ion migration
- Greatly speeds up the process by making it easier for atoms to move from one mineral grain to another by putting water in the pore spaces between them.
- Hydrothermal
- mineral-rich water heated by magma moves through rock changing it. Most radical form of metamorphism. It can remove elements and add others not originally present. All other types reshuffle atoms.
- Sandstone
- Medium-grained. Mostly quartz and feldspar. Forms from beaches_ sandbars_ and dunes.
- Crystallization/Recrystallization
- Formation of a mass of interlocking crystals. Due to direct precipitation, or growth around previously formed crystals or shells
- Conglomerate
- Coarse-grained. Mix of smooth_ rounded quartz gravel and sand. Forms from shallow_ turbulent environments i.e. gravel bars and pebble beaches.
- Reservoir rock
- Rock in which oil and gas are stored in pores and cracks
- Contact metamorphism
- caused by the effects of a magma intrusion (pluton). A portion of the surrounding rock is changed.
- Bedrock
- The rock zformation that lies beneath the soil. Soil formed from it is called or residual soil.
- Carbonate Rocks
- Made of materials i.e. calcite and dolomite. Usually form in warm (tropical to subtropical), shallow (continental shelf) ocean environments. Common types (limestone and dolostone).
- Fossil Fuels
- Burnable geological deposits of organic hydrocarbons (compounds of hydrogen and carbon, and sometimes other elements). Most of our energy is from the burning of these.
- Oil trap
- a structure (fold or fault)_ or a sequence of strata that gathers oil and gas into a relatively small area.
- Marble
- Visibly crystalline. Sometimes has bands of color. Mostly calcite or dolomite. Forms from limestone or dolostone (carbonate rocks).
- Exfoliation dome
- Dome like rock mass. Associated with large plutons (stocks and batholiths)
- Mass Wasting
- Downslope movement of rock and soil under the influence of gravity