Geology and the Environment - Unit 3 Flashcards
Ablation
The loss of glacier ice by meltin or evaporation
Abrasion
Erosion by wind transported sediment or by the scraping of rock fragments frozen in glacial ice
Active Margin
A continental margin at which there is significant volcanic and earthquake activity; commonly, a convergent plate margin
Active Volcano
A volcano wit a record of eruption within recent history
Aftershocks
Earthquakes that follow the main shock when a fault has slipped; of magnitude equal to or lower than the main shock
Alpine Glacier
A glacier occupying a valley in mountainous terrain
Andesite
Volcanic Rock intermediate in composition between basalt and rhyolite
Angle of Repose
The maximum slope angle at which a given unconsolidated material is stable
Barrier Islands
Long, low, narrow islands parallel to the coastline that protect the coastline somewhat from wave action
Basalt
A volcanic rock rich in ferromagnesian minerals; relatively low silica
Beach
Gentyly sloping shoreline area washed over by waves
Beach Face
The part of the beach along the water that is regularly washed by waves
Body Waves
Seismic waves that pass through the earth’s interior; includes P waves and S waves
Caldera
A large, bowl-shaped summit depression in a volcano; may be formed by explosion or collapse
Calving
The formation of icebergs by the breakup of a glacier flowing out over water
Cinder Cone
A volcano built of cinders and other pyroclastics piled up around the volcanic vent
Composite Volcano
Stratovolcano:A composite volcanic cone built of interlayered lava flows and pyroclastic materials
Continental Glacier
A large glacier covering extensive land area; also known as an ice cap or ice sheet; may be several Km thick
Creep (Fault)
The slow, gradual slip along a fault zone without major, damaging earthquakes
Creep (Rock or Soil)
Slow, gradual downslope movement of unstable surficial materials (as contrasted with more abrupt landslides)
Debris Avalanche
A mixed flow of rock, soil, vegetation, or other materials
Debris Flow
Another term for debris avalanche; especially used for a water-saturated one
Deflation
The wholesale removal of loose sediment by wind erosion
Desert
A baren region incapable of supporting appreciable life
Desertification
The process by which marginally habitable arid lands are converted to desert; typically accelerated by human activities
Dip-Slip Fault
A fault with predominently vertical displacement
Dormant Volcano
A volcano with no recent eruptive history but that still looks relatively fresh and unweathered; may become active again in future
Drift
Sediment transported and deposited by a glacier; Also called Outwash
Drowned Valley
Along a coastline, a stream valley that is partially flooded by seawater as a consequence of land sinking and/or sea level rising
Dune
A low mound or ridge of sediment (usually sand) deposited by wind
Earthquake
Ground displacement and energy release associated with the sudden motion of rocks along a fault
Earthquake Cycle
The concept that there is a periodic quality about the occurrence of major earthquakes on a given fault zone, with repreated cycles of stress buildup, ryupture, and relaxation
Elastic Rebound
Phenomenon whereby stressed rocks snap back elastically after an earthquake to their pre-stress condition
Epicenter
The point on the earth’s surface directly above the focus of an earthquake
Equilibrium Line
Line on the surface of a glacier at which accumulation just equals ablation
Estuary
A body of water along a coastline that contains a mix of resh and salt water
Extinct Volcano
A Volcano that has no recent eruptive history and appears very weathered; not expected to erupt again
Fall (Rock)
Mass wasting by free-fall of material not always in contact with the ground underneath
Fault
Planar break in rock along which one side has moved relative to the other
Fissue Eruption
The eruption of lava from a crack in the lithosphere, rather than from a central vent
Flow
Mass wasting in which materials move in chaotic fashion
Focus
The point of first break on a fault during an earthquake
Glacier
A mass of ice that moves or flows over land under its own weight
Intensity
A measure of the damaging effects of an earthquake at a particular spot; commonly remported on the Modified Mercalli Scale
Lahar
A Volcanic mudflow deposit formed from hot ash and water, the latter often derived from melting snow on a snow-capped or glaciated volcano
Landslide
A general term applied to a rapid mass-wasting event
Lava Dome
A compact, bulbous, steep-sided structure built of very viscous, silicic lava emitted from a central pipe or vent
Liquefaction (soil)
A quicksand condition arising in wet soil shaken by seismic waves; soil loses its strength as particles lose contact with each other
Littoral Drift
Sand movement along the length of a beach
Loess
Wind-deposited sediment composed of fine particles (0.01-0.06 mm in diameter)
Longshore Current
Net movement of water parallel to a coastline, arising when waves and currents approach the shore at an oblique angle
Magnitude
Measure of earthquake size; often reported using the Richter Magnitude Scale
Mass Movement
Also called Mass Wasting: The downslope movement of material due to gravity
Mass Wasting
The downslope movement of material due to gravity; also known as mass movement
Milling
Erosion by the grinding action of sand-laden waves on a coast
Moraine
Landform made of till
Outwash
Glacial sediment moved and redeposited by meltwater
P Waves
Compressed seismic body waves
Passive Margin
A geologically quiet continental margin, lacking significant volcanic or seismic activity
Phreatic Eruption
A violent, explosive volcanic eruption lake a steam-boiler explosion, occuring when subsurface water is heated and converted to steam by hot magma underground
Precursor Phenomena
Phenomena that precede an earthquake, volcanic eruption, or other natural event, which may be used to predict the upcoming event
Pyroclastic Flow
Denser than air flow of hot gas and ash from a volcano
Pyroclastics
The hot fragments of rock and magma emitted during an explosive volcanic eruption
Quick Clay
The sediment formed from glacial rock flour deposited in a marine setting, weakened by subsequent flushing with fresh pore water
Rain Shadow
A dry zone landward of a mountain range, which is caused by loss of moisture from air passing over the mountains
Rhyolite
Silica rich volcanic rock; the volcanic compositional equivalent of granite
Rock Flour
A fine sediment of pulverized rock produced by glacial erosion
Rockfall
Mass wasting by free-fall of material not always in contact with the ground underneath
S Waves
Shear seismic body waves; do not propagate through liquids
Seismic Gap
A section of an active fault along which few earthquakes are occuring, in contrast to adjacent fault segments; presumably, a locked section of fault
Seismic Waves
The fomr in which most energy is released during earthquakes; divided into body waves and surface waves
Seismograph
An instrument used to measure ground motion caused by seismic waves
Sensitivity Clay
A material similar in behaviour to quick clay, but derived from different materials, such as volcanic ash
Shear Strength
The ability of a material to resist shearing stress
Shearing Stress
Stress that tends to cause different parts of an object to slide past each other across a plane; with respect to mass movements, stress tending to pull material downslope
Sheild Volcano
A low, flat, gently sloping volcano built from many flows of fluid, low viscosity basaltic lava
Slide
A form of mass wasting in which a relatively coherent mass of material moves downslope along a well defined surface
Slip Face
The downward side of a dune, on which material tends to assume the slope of the angle of repose of the sediment of the dune
Slump
A slide moved only a short distance, often with a rotational component to the movement
Stike-Slip Fault
A fault with predominantly horizontal displacement
Stratovolcano
A composite volcanic cone built of interlayered lava flows and pyroclastic materials
Striations
Parallel grooves in a rock surface cut when a glacier containing rock debris flows over that rock
Surface Waves
The seismic waves that travel along the earth’s surface
Surge (Storm)
Localized increase in water level of an ocean or large lake; caused by extreme low pressure and high winds associated with major storms
Talus
Accumulated debris from rockfalls and rockslides
Thrust Fault
A reverse fault with very shallowly dipping fault plane
Till
Poorly sorted sediment deposited by melting glacial ice
Tsunami
A seismic sea wave, generated by a major earthquake in or near an ovean basin; sometimes incorrectly called a Tidal Wave
Ventifact
Literally wind made rock shaped by wind erosion
Volcanic Explosivity Index
A scale for reporting the size of an explosive volcanic eruption
Wave Refraction
The deflection of waves as they approach the shore
Wave-Cut Platform
Step-like surface cut in rock by wave action at sea or lake level
