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193 Cards in this Set
- Front
- Back
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geologic time scale |
summarytimeline of all earth history, reflects currently accepted names of timeintervals for each segment of Earth’s history from vast eons through briefereras, periods and epochs
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relative time |
what happened in order; sequence of events based on the relative positions of rock strata above/below eachother; based on superposition- rock/sediment always are arranged with youngest beds "supoposed" toward the top of a rock formation and the oldest at the base if not disturbed |
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absolute time |
actual number of years before the present; determined by scientific methods like radiometric dating |
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uniformitarianism |
same physical processes active in the environment today have ben operating throughout geologic time |
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holocene |
youngest epoch consisting of the last 11,500 years since the retreat of the continental glaciers |
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uniformitariansism |
same physiacl processes active in the environment today have been operating throughout geologic time |
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where are the oldest materials in earths crust, and how old are they? |
W. australia, 4.2-4.4 billion years old |
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how is earths interior sorted? |
sorted in concentric layers, each distinct in chemical composition or temperature |
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how has the earth been thought to condense/congeal? |
from a nebula of dust/gas/icy comets about 4.6 billion years ago |
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how does heat energy migrate? |
it migrates outward from the center by conduction and physical convection in the more fluid or plastic layers in the mantle and neart the surface |
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inner core |
thought to be solid iron that is well above the melting temperature, but remains sold bc of intense pressure |
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outercore |
made of molten, metallic iron with lighter densities than the inner; fluid outercore generates at least 90% of earths magnetic field and the magnetopshere that surrounds and protects earth from solar, wind and cosmic radiation; circulation in outercore converts thermal and gravitational energy into magnetic energy producing earths magnetic field |
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zone of discontinuity |
dividing earths outercore from the mantle, or a place where physical differences occur between adjoining regions in earths interior |
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80% of earths total volume |
lower and upper mantle |
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mantle |
rich in oxides of iron, magnesium and silicates which are dense adn tightly packed at depth, grading to lesser densities toward the surface |
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temperature in the mantle |
gradual temperature increase with depth and a stiffening due to increased pressures |
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lower mantle |
denser, thought to contain a mixture of iron, magnesium and silicates with some calcium and aluminum |
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upper mantle |
divides into 3 distinct layers, upper mantle, asthenosphere and upper most mantle |
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lithosphere |
made up of upper most mantle witht he crust |
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asthenosphere |
below lithosphere (aka plastic layer) contains pockets of increased heat from radioactive decay and is susceptible to slow convective currents in hotter/less dense materials; least rigid region of the mantle with densities avg. 3.3gcm^3; about 10% is molten in uneven patterns and hot spots; slow movement in this zone disturbs the overlying crust and creates tectonic activity |
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oceanic crust |
basalt, granular and high in silica, magnesium and iton (can be called sima) thin and dense |
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continental crust |
essentially granite, crystalline and high in silica, aluminum, potassium, calcium and sodium (can be called sial) about 2.7g/cm^3 |
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isostacy |
explains certain vertical movement of earths crust due to bouyancy and balance; entire crust is in a constant state of compensating adjustment or ".." slowly rising and sinking in response as it is pushed/dragged and pulled over the asthenosphere |
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endogenic |
internal system builds landforms |
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exogenic |
external system wears down landforms |
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geologic cycle |
give and take of the earths atmosphere; fueled from earths internal heat and solar energy from space influenced by leveling forces of gravity |
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what is the geologic cycle composed of? |
hydrologic cycle (erosion, transportation and deposition) rock cycle (3 types of rocks found in the crust, igneous, sedimentary and metamorphic) tectonic cycle (brings heat energy adn new material to the surface and recycles materal, creating movement adn deformation of the crust |
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deposition |
processes earths materials with chemical/physical action of water ice and wind |
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what is the most reactive gas in the lower atmosphere readily combining with other elements? |
oxygen |
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minerals |
formed from earths elements; "song" |
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mineral is characterized by... |
hardness, color, density etc |
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widespread mineral families are... |
silicates (silicon/oxygen are common and readily combine with eachother and other elements; makes up 95% of earths crust) oxides (oxygen combine with metallic elements like iron) carbonates (carbon in combination with oxygen and other elements: calcium, magnesium, potassium) |
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rock |
assemblages of minerals bound together (granite) or a single mass of mineral (rock salt) or undifferentiaed material (obsidian) or solid organic material (coal) |
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why are continents adrift? |
convection currents in the asthenosphere adn upper mantle dragging them around |
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Sir Francis Bacon |
similarities between S. America and Africa |
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alfred wegener |
"origins of the continents and ocean" father of continetnal drift (pangea in triassic period) |
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plate tectonics |
include processes of upwelling magma; lithospheric plate movement (seafloor spreading) adn lithospheric subduction (earthquakes, volcanic activity) and lithospheric deformation (warping, folding and faulting) |
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sea floor spreading |
mechanism that builds mountain chains and drives continental movement; submarine mountain ranges were mid ocean ridges adn the direct result of upwelling flows of magma from hot areas in the upper mantle and asthenosphere |
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magnetic tape recording in the sea floor |
determined by earths reorientation of polarity during sea floor spreading |
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why is sea floor relatively young? |
no more than 208 million years old becayse the farthest sections from the mid ocean ridges are slowly plunging beneath the continental crust and are reforming |
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divergent boundaries |
characteristic of sea floor spreading centers where upwelling material from the mantle forms new seafloor and lithospheric plates spread apart (zone of tension) most ".." occur at mid ocean ridges, few occur within continents |
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convergent boundaries |
characteristic of collision zones where areas of continental and oceanic lithosphere collide (zones of compression) |
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transform boundaries |
occur where plates slide laterally past one another at right angles to a sea floor spreading center (no volcanic eruptions); spreading center mid ocean ridges are the location of transform faults |
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igneous rock |
solidifies and crystallizes from a molten state; cooling history determines its physical characteristics. coarse grained (flower cooling) or fine grained/glassy (faster cooling); makes up approx 90% earths crust |
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intrusive igneous rocks |
cools slowly in the crust, forms pluton |
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extrusive igneous rocks |
formed through volcanic eruptions adn flows (lava that cools forms basalt) |
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how are igneous rocks classified? |
through mineral composition and texture with 2 broad categories: felsic and mafic
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felsic |
derived both in composition and in name from feldspar and silica, high in silica, aluminum, potassium and sodium; low melting points, generally lighter in color and less dense |
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mafic |
derived both in composition and name from magnesium and ferric; low in silica high in magnesium and iron; high melting points darker in color with greater density |
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sedimentary rock |
solor energy and gravity drive the process of sedimentation with water; existin grock is disintegrated and dissolved by weathering, picked up/moved by erosion and transportation adn deposited along river, beach, ocean sites; involves lithification (process of cementation, compaction and hardening of sediments) |
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what are 2 primary sources of sedimentary rocks?
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clastic sediments (formed from mechanically transported fragments of older rocks) and chemical sediments (from dissolved minerals in solution, some having organic origins) also biological |
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clastic sedimentary rocks |
weathered and fragmented rocks that are further worn in transport provide clastic sediments; clast sizes range from boulders to microscopic clay particles and the form they take as lithified rock |
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chemical sedimentary rocks |
formed not from physical pieces of broken rocl but from dissolved minerals, transported in solution and chemically precipitated from solution; once formed they are vulnerabe to chemical weathering |
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metamorphic rock |
may be transformed from igneous/sedimentary; goes through profound physical/chemical changes under pressure and increased temperature; generally more compact than original rock adn are harder/most resistant to weathering/erosion; compressed during collisions between slabs of earths crust |
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continental landmasses |
portions of crust that reside abover or near sea level including the undersea continental shelves along coastlines |
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ocean basins |
enirely below sea level |
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tectonic activity |
driven out by planets internal energy builds crust while exogenic processes of weathering/erosion, powered by the sun through actions of air, water, waves and ice tear down crust, generally slow requiring millions of years |
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what is the craton or heartland region of the continental crust? |
Allcontinents have a nucleus of ancient crystalline rock on which the continent“grows” witht eh addition of crustal fragments and sediments;Cratons are generally eroded to a low elevationand relief; most date to Precambrian and can be more than 2 billion years old
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continental shield |
region where a craton is exposed at the surface |
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what are three types of stress? |
tension (stretching), compression (shortening) and shear (twisting/tearing); stress is a force and the resulting strain is the deformation in the rock |
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fault zones |
areas where fractures in the rock demonstrate crustal movement; at the moment of a fracture, a sharp release of energy occurs producing an earthquake |
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fault plane |
fracture surface along which the two sides of a fault move |
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when does a normal fault form? |
when rocks are pulled apart by tensional stress; when the break occurs rock on one side moves vertically along aninclined fault plane, the downward shifting side is the hanging wall, it dropsrelative to the footwall block; a cliff formed by faulting is commonly called afault scarp/escarpmentts" |
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when does a thrust/reverse fault form? |
when rocks are forced together by compressional stress; converging plates force rocks to move upwardalong the fault plane; appears similar to a normal fault although but with morecollapse and landslides occur from the hanging wall component |
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when does a strike slip fault form? |
when rocks are torn by lateral shearing stress; themovement is right lateral or left lateral depending on the motion perceivedwhen you observe movement on one side of the fault relative to the other side;can create linear rift valleys |
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orogenesis |
birth of mountain; mountain building; net result of this accumulating material is a thickening of the crust |
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oceanic-continental plate collisions |
occurring along the pacific coast of theAmericas and has formed the andes and sierra of central America; there arefolded sedimentary formations with intrusions of magma forming granitic plutonsat the heart of these mountains; active around the pacific rim, thermal innature because the dividing plate melts and migrates back toward the surface asmolten rock; known as circumpacific belt or ring of fire |
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oceanic-oceanic plate collision |
collisions can either produce simple volcanicarcs or more complex arcs such as Indonesia and japan (which includedeformation and metamorphism of rocks and granitic intrusions) these processesformed the chains of island arcs and volcanoes that continue from thesouthwestern pacific to the western pacific, and the Philippines; active aroundthe pacific rim, thermal in nature because the dividing plate melts andmigrates back toward the surface as molten rock; known as circumpacific belt orring of fire
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continental-continental plate collision |
largemasses of continental crust are subjected to intense folding, overthrusting,faulting and uplifting; converging plates crush and deform both marinesediments and basaltic oceanic crust; (ex. formation of European alps); as aresult of such compression forces includes considerable crustal shortening,formed great overturned folds called nappes
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focus/hypocenter of an earthquake |
subsurface area along a fault plane where the motion of seismic waves is initiated |
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what is the area at the surface directly above the focus called> |
epicenter |
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what are tectonic earthquakes associated with? |
faulting |
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seismograph |
instrument used to record vibrations transmitted as waves of energy throughout earth's interior and in the crust; this device helps scientists to rate earthquakes on a qualitative and quantitative level |
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qualitative scale |
damage intensity scale |
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quantitative scale |
magnitude of energy released scale |
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mercalli scale |
measure damage intensity on a roman numeral scale 1-12 |
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richter scale |
a system designed to estimate earthquake magnitude, records the amplitude of seismic waves; is logarithmic where each whole number represents a ten fold increase in the measured wave amplitude |
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elastic rebound theory |
how a fault breaks; 1. Generally, two sides along a fault appear to belocked by friction, resisting any movement despite the powerful forces actingon the adjoining pieces of crust 2. Stress continues to build strain along the faultplane surfaces, storing elastic energy 3. When strain build up finally exceeds frictionallock, both sides of the fault abruptly move to a condition of less strain,releasing a burst of mechanical energy |
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how many volcanoes erupt worldwide per year? |
50 |
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volcano |
forms at the end of a central vent/pipe that rises from the asthenosphere and upper mantle through the crust into a volcanic mountain |
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crater |
circular surface depression usually forms at or near the summit |
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lava (molten rock) |
gases and pyroclastics pass through the vent to surface and build the volcanic landform; can occur in many different textures and forms which accounts for the varied behavior of volcanoes adn the different landforms and their origins |
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location of volcanic mountains on earth is a function of... |
plate tectonics and hot spring activity |
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volcanic activity occurs in 3 settings |
1.Along subduction boundaries at continentalplate-oceanic plate convergence (Mt. St. Helens) or oceanic plate-oceanicconvergence (Philippines/Japan)2.Along seafloor spreading center on the oceanfloor (Iceland on Mid Atlantic Ridge) and along areas of rifting on continentalplates (rift zone in E. Africa)3. At hot spots where individual plumes of magmarise to the crust (Hawaii and Yellowstone) |
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what are the factors determining an eruption? |
1. Magmas chemistry (related to its source) 2. Magmas viscosity (resistance to flow “thickness”)
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what are the 2 types of eruptions? |
effusive and explosive |
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effusive eruptions |
relatively gentle but produce enormous volumes of lava annually on the seafloor and in Hawaii and Iceland; direct eruptions from the asthenosphere and upper mantle produce low viscosity magma that is fluid and cools to form a dark basaltic rock low in silica and rich in iron and magnesium; gases readily escape from this magma bc of low viscosity, adding to a gentle eruption with relatively small explosions and few pyroclastics
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• Typical mountain landform built from effusive eruptions is gently sloped, gradually rising from the surrounding landscape to a summit crater ; known as a
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shield volcano |
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explosive eruptions |
volcanic activity inland from subduction zones produces explosive volcanoes; magma produced by the melting of subducted oceanic plate and other materials is thicker (more viscous) than magma that forms from effusive volcanoes, it is 50-75% silica and high in aluminum, consequently it tends to block the magma conduit inside the volcano, the block traps and compresses gases causing pressure to build for a possible explosive eruption
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composite volcano |
- is a explosively formed volcano (stratovolcano) built up in alternating layers of ash, rock and lava; tend to have steep sides, are more conical in shape; high viscosity , rising magma forms a plug near the surface where the blockage causes tremendous pressure, it then erupts producing much less lava than effusive, but larger amounts of pyroclastics (volcanic ash, dust, cinders, lapilli, scoria, pumice and aerial bombs (blobs of lava that were ejected)
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nuee ardente |
"glowing coud" is an incandescent, hot, turbulent fas, ash and pyroclastic cloud that can jet across the landscape in an eruption |
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low viscosity |
very fluid |
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high viscosity |
thick and flowing slowly |
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geomorphology |
science of landsforms, their origin, evolution, form and spatial distribution |
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denudation |
any process that wears away or rearranges landforms; principal denudation processes affection surface materials include weathering, mass movement, erosion, transportation, and deposition as produced by the agents of moving water, air, waves and ice (all influenced by the pull of gravity) |
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landscape |
an open system with highly variable inputs of energy and materials |
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potential energy of position |
created by uplift above sea level and therefore disequilibrium and imbalance between relief and energy |
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heat energy |
converted from suns radient energy |
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kinetic cycle |
imparted through the hydrologic cycle through mechanical motion |
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chemical energy |
made available from the atmosphere and various actions within the crust |
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geomorphic threshold |
point at which energy overcomes resistance against movement; system breaks through to a new set of equilibrium relationships as the landform and its slopes enter a period of adjustment and realignment
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weathering |
process that breaks down rock at earth’s surface and to some depth below the surface, either disintegrating rock into mineral particles or dissolving it in water; this process is both physical (mechanical) and chemical; the interplay of the 2 is complex, often forming a synergy, a combined action, as the suite of processes work the rock
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bedrock |
parent rock from which weathered regolith and soils develop |
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factors influencing weathering processes |
- Rock composition and structure (jointing): jointing in rock is important for weathering processes; joints are fractures or separations in rock that would occur without displacement of the sides- Climate: precipitation, temperature and freezethaw cycles are the most important factors affecting weathering - Subsurface water- influences through water table level and water movement within soil and rock structures- Slope orientation: geographic orientation of a slope; whether it faces north, south, east or west, controls the slopes exposure to sun, wind and precipitation; slopes facing away from the sun’s rays tend to be cooler, moister and more vegetated than slopes in direct sunlight- Vegetation: can protect rock by shielding fit from raindrop impact and providing roots to stabilize soil; also produces organic acids from partial decay of organic matter; plant roots can enter crevices and break up a rock
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physical weathering |
when rock is broken and disintegrated without any chemical alteration (aka mechanical weathering); by breaking up rock, physical weathering produces more surface area on which chemical weathering may operate |
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types of mechanical weathering |
- Frost action: when water freezes its volume expands as much as 9%, this expansion creates a powerful mechanical force which can exceed the tensional strength of rock; repeated freezing/expanding and thawing/contracting of water breaks rocks apart; joint block separation- occurs along existing joints and fractures; frost wedging- ice begins in small openings gradually expanding until rocks are cleaved or split- Salt crystal growth (salt weathering): dry weather draws moisture to the surface of rocks, as the water evaporates, dissolved minerals in the water grow crystals In a process known as crystallization - Pressure release jointing: layer after layer of rock peels off in curved slabs or plates, thinner at the top of the rock structure and thicker at the sides; as these slabs weather, they slip off in the process of sheeting; this exfoliation process creates arch shaped and dome shaped features on the exposed landscape
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chemical weathering |
chemical breakdown of the constituent minerals in rock, always it the presence of water; chemical decomposition and decay become more intense as both temperature and precipitation increase; ex). spheroidal weathering- water penetrates joints/fractures and dissolves the rocks weaker minerals or cementing materials
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types of chemical weathering |
- Hydrolysis: when minerals chemically react with water; decomposition process that breaks down silicate minerals in rocks; involves water and elements in chemical reactions to produce different compounds; ex). weathering of feldspar minerals in granite can be caused by a reaction to the normal mild acids dissolved in precipitation; granular disintegration- when weaker minerals in rock are changed by hydrolysis, the interlocking crystal network breaks down so the rock fails, this is when “…” takes place- Hydration: “combination with water” little chemical change, water becomes part of the chemical composition of the mineral- Oxidation: certain metallic elements combine with oxygen to form oxides; most familiar is rusting; as iron is removed from the minerals in a rock, the disruption of the crystal structures makes the rock more susceptible to further chemical weathering and disintegration- Dissolution of carbonates: when a mineral dissolves into solution; water is universal solvent bc its capable of dissolving at least 57 of the natural elements and many of their compounds; carbonation- a reaction whereby carbon combines with minerals, dissolving them
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characteristics of limestone |
abundant on earth and composes many landscapes; these areas are susceptible to chemical weathering, which creates a specific landscape of pitted, bumpy surface topography, poor surface drainage, and well developed solution channels
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karst topography |
approx.. 15% of earth’s land area has some karst features with outstanding examples found in southern china, japan, Puerto rico, cuba the Yucatan of mexico, Kentucky, Indiana, new mexico and florida; approx.. 28% of Kentucky has sinkholes and related karst features noted on topographic maps
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for a limestone landscape to develop into karst topography, several conditions are necessary |
- Limestone formation must contain 80% of more calcium carbonate for dissolution processes to proceed effectively- Complex patterns of joints in the otherwise impermeable limestone are needed for water to form routes to subsurface drainage channels- An aerated (containing air) zone must exist between the ground surface and water table- Vegetation cover is required to supply varying amounts of organic acids that enhance the dissolution process
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where does karst occur> |
in arid regions, but primarily due to former climatic conditions of greater humidity
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sinkholes |
weathering of limstone landscapes create sinkholes which form in circular depressions; collapse sinkhole forms if such a solution sinkhole collapses through the roof of an underground cavern |
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karst valleys can be formed from.... |
the continuation of solution and collapse which coalesce to form a karst valley which is an elongated depression up to several km long |
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in wet tropics, karst topography forms in deeply joined... |
thick limestone beds |
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where do caves form? |
• caves generally form just beneath the water table where later lowering of the water level exposes them to further development
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stalacites stalagmites |
grow from the ceiling build from the floor |
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mass movement |
any unit movement of a body of material propelled and controlled by gravity; can be surface processes or submarine landslides beneath the ocean; content can range from dry to wet, slow to fast, small to large and free falling to gradual/intermittent
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mass wasting |
general process involved in mass movements and erosion of the landscape |
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angle of repose |
steepness of something; angle represents a balance of the driving force (gravity) and resisting force (friction/shearing); the angle ranges for various materials at 33-37 degrees and for snow avalanche slopes between 30-50 degrees
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what materials are highly susceptible to hydration? |
clays, shales and mudstones |
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what are the 4 classes of mass movement? |
rock fall, debris avalanche, landslides, flows and creep |
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rock fall |
volume of rock that falls through the air and hits a surface; during “..” individual pieces fall independently and characteristically form a cone-shaped pile of irregular broken rocks on a talus slope at the base of a steep incline
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debris avalanche |
mass of falling/tumbling rock, debris and soil; speed often results from ice and water that fluidize the debris avalanche results from its tremendous speed and ack of warning; Peruvian Andes 1970, earthquake initiated the event and upward 100 million m^3 of debris buried the city of Yungay, where 18,000 people perished and the avalanche attained velocities of 300kmph
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landslides |
sudden rapid movement of a cohesive mass of regolith/bedrock that is not saturated with moisture; large amount of material failing simultaneously; to eliminate the surprise element scientists use the GPS to measure slight land shifts; slides occur in 2 basic forms:1. Translational slides- movement along a planar (flat) surface toughly parallel to the angle of the slope with no rotation; ex). Madison Canyon slide; flow and creep patterns are also considered “…” in nature2. Rotational slides- occur when surface material moves along concave surface; underlying clay presents an impervious surface to percolating water, so water flows along the clay surface; ex). La Conchita, California
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flows |
include earth flows and more fluid mudflows; heavy rains can saturate barren mountain slopes and send them moving
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creep |
persistent gradual mass movement of surface soil; individual soil particles are lifted/disturbed by the expansion of soil moisture as it freezes by cycles of moistness and dryness; in freeze thaw cycle particles are lifted at right angles to the slope by freezing soil moisture, but when the ice melts the particles fall straight downward in response to gravity; fence posts, trees go down with; strategies used to arrest the movement are grading the terrain, building terraces and retaining walls
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what do rivers do? |
• Rivers redistribute mineral nutrients important for soil formation and plant growth, and serve society in many ways• Shape the landscape by removing products of weathering, mass movement and erosion and transporting them downstream• Rivers provide with essential water supply and receive, dilute and transport wastes, provide critical cooling water for industry and for, one of the world’s most important transportation networks
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hydrology |
science of water and its global circulation, distribution and properties, specifically water at and below earth surface |
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discharge |
streamflow volume past a point in a give unit of time |
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rivers with greatest stream discharge |
amazon, congo, yangtze, orinoco and in US missouri-ohio-mississippi, st. lawrence and mackenzie river systems |
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what are the driving forces of the fluvial systems |
insolation and gravity power the hydrologic cycle |
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erosion |
process of water dislodging, dissolving and moving surface material• Streams produce fluvial erosion in which weathered sediment is picked up for transport to new locations; thus a stream is a mixture of water and solids; the solids are rolled/carried by mechanical transport or move in a dissolved solution; materials are laid down by the process of deposition
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alluvium |
clay, silt, sand, gravel and mineral fragments deposited by running water, which can be semi/sorted sediment on a floodplain, delta or streambed
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base level |
a level below which a stream cannot erode its valley, ultimate base level is sea level, the average between high/low tides
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local base level |
(or temporary) may control the lower limit of local streams for a region; local base may be a rover, lake, hard/resistant rock, or the reservoir formed by a human made dam
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landforms are produced by 2 basic processes... |
1. Erosive action of flowing water 2. Deposition of stream transported materials• Drainage basin- ever stream has
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drainage basin |
every stream has a “..” ranging in size from tiny to vast; ridges form drainage divides that define the catchment (water receiving) area of every drainage basin; ridges are dividing lines that control into which basin runoff water from precipitation drains
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how does water flow in a drainage basin? |
• In any drainage basin, water initially moves downslope in a thin film of sheetflow or overland flow
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rills |
small scale downhill grooves that may develop into deeper gullies and then into a stream in a valley |
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continental divides |
are situated in the US and Canada, are extensive mountain and highland regions separating drainage basins, sending flows to the Pacific, Gulf of MX, Atlantic, Hudson bay or Arctic ocean; these divides form water resource regions and provide a spatial framework for water management planning
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drainage basins as open systems |
ex. Danube river; inputs include, precipitation and minerals of rocks of the regional geology; energy and materials are redistributed as the stream constantly adjusts to its landscape; system outputs of water and sediment disperse through the mouth of the river into a lake or ocean
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drainage denisty |
primary feature of any drainage basin determined by dividing the total length of all stream channels in the basin by the area of the basin
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drainage pattern |
arrangement of channels in an area, quite distinctive for they are determined by a combination of regional steepness, variable rock resistance/climate/hydrology, relief of the land and structural controls imposed by underlying rocks
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dendritic drainage |
most common, a treelike pattern, similar to many natural systems (capillaries in humans, patterns in leaves); energy expended by this drainage system is efficient because the overall length of the branches is minimized
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trellis drainage |
pattern is characteristic of dipping/folded topography; exists in the nearly parallel mountain folds of the ridge and valley province in E. US
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how are drainage patterns influenced |
• Drainage patterns are influenced by rock structures of variable resistance and folded strata; parallel folded structures direct the principal streams, whereas smaller dendritic tributary streams are at work on nearby slopes
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radial drainage |
pattern results when streams flow off a central peak/dome, such as occurs on a volcanic mountain
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rectangular |
formed by a faulted and jointed landscape which directs stream courses in patterns of right angle turns
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parallel drainage |
associated with steep slopes
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annular |
produced by structural domes with concentric patterns of rock strata guiding stream courses |
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derenaged |
occurs in areas with disrupted surface patterns (glaciated sheild regions of canada) no clear geometry in the drainage and no true stream valley pattern |
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stream water; potential energy to kinetic |
• A mass of water positioned above base level in a stream has potential energy; as water flows downslope or downstream, under the influence of gravity the energy becomes kinetic; the rate of the conversion from pot. To kin. Energy depends on the steepness of the stream channel and volume of water involved
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discharge |
streamsvolume of flow per unit of time, is dependent upon stream channel width anddepth and on the velocity of the flow?
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Q=WDV |
• Q- discharge; w- channel width; d- channel depth; v- stream velocity
• Q increases in a downstream direction with inflow from tributaries, some combination of channel width/depth and stream velocity must also increase• Greater discharge increases the velocity and therefore the capacity of the river to transport sediment as the flood progresses |
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competence |
streams ability to move particles of a specific size is a function of stream velocity and energy available to suspend materials
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capacity |
total possible load that a stream can transport; 4 processes transport eroded materials: solution, suspension, saltation and traction
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solution |
dissolved load of a stream, esp. the chemical solution derived from minerals such as limestone/dolomite/soluble salts
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suspended load |
consist of fine grained, clastic particles (bits/pieces of rock); they are held aloft in the stream with the fines particles not deposited until the stream velocity slows nearly to 0
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bedload |
coarser materials that are dragged, roller or pushed along the stream bed by traction or saltation |
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saltation |
referring to the way particles bounce along in short hops and jumps; particles that move in this way are too large to remain in suspension but not limited to sliding and rolling |
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braided stream |
maze of interconnected channels which often occurs when reduced discharge lowers a streams transporting ability such as after flooding, commonly occur in glacial environments
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where are the greatest and lowest velocities in a stream? |
• Greatest velocities in a stream are near the surface at a center channel corresponding to the deepest part of the stream channel• Velocities decrease closer to the sides and bottom of the channel because of frictional drag on the water flow
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undercut bank |
in streams a steep bank formed along the outer portion of a meandering stream; produced by lateral erosive action of a stream; sometimes called a cutbank
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point bar |
a deposit of the inner portion of a meander that experiences the slowest water velocity and thus receives sediment fill
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oxbow lake |
· when former meander becomes isolated from therest of the river that may gradually fill with organic debris and silt or mayagain become part of the river when it floods
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gradient |
degree of inclination; or decline in elevation from its headwaters to its mouth |
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graded stream |
an idealized condition in which a streams load and the landscape mutually adjust; forms a dynamic equilibrium among erosion, transported load, deposition and streams capacity
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dynamic eqilibrium |
when channels adjust their slope size and shape so that a stream has just enough energy to transport its sediment load
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nickpoint |
when the longitudinal profile of a stream shows an abrupt change in gradient or a point of interruption (water fall or area of rapids); can result when a stream flows across a zone of hard, resistant rock or from various tectonic uplift episodes• Temporary blockage in a channel caused by a landslide or logjam can also be considered a nickpoint
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flood plain |
flat, low lying area flanking many stream channels that is subjected to recurrent flooding; formed when river overflows its channel during times of high flow
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delta |
level of nearly level depositional plain that forms at the mouth of a river |
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distributaries |
smaller courses divded from channels |
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birds foot delta |
long channel with many distributaries and sediments carried beyond the tip of the delta into the gulf of mexico
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flood |
high waterflow that overflows the natural bank along any portion of a stream |
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hydrograph |
graph of stream discharge over time for a specific location |
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eolian |
work of wind erosion, transportation and deposition |
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winds ability to move materials |
• Ability of wind to move materials is actually small compared with that of other transporting agents such as water and ice bc air is so much less dense than those other media• Over time wind accomplishes enormous work
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grain size and wind erosion |
intermediate sized grains move most easily (bounce along); largest and smallest sand particles require the strongest winds to move; large particles are heavier and require stronger winds, smaller particles are difficult to move because they exhibit a mutual cohesiveness and usually present a smooth surface to the wind• Finest dust once aloft is carried from continent to continent
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wind erosion processes |
deflation and abrasion |
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deflation |
removal and lifting of individual loose particles; blows away loose or noncohesive sediment and works with rainwater to form a surface resembling a cobblestone street- Desert pavement: protects underlying sediment from further deflation and water erosion- Windblown particles settle between and below coarse rocks and pebbles that are gradually displaced upward- Rainwater is involved as wetting and drying episodes swell and shrink clay sized particles
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abrasion |
grinding of rock surfaces by “sand blasting” action of particles captured in the air- Especially effective at polishing exposed rocks when the abrading particles are hard and angular- Variables that affect the rate of abrasion include the hardness of surface rocks, wind velocity and wind consistency- Abrasive action is restricted to the area immediately above the ground no more than a meter or two in height because sand grains are lifted only a short distance- Rocks exposed to eolian abrasion appear pitted, fluted (grooved) or polished
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ventifacts |
rocks that have evidence of eolian erosion; piece of rock etched and smoothed by eolian erosion |
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yardangs |
streamline rock structure formed by deflation and abrasion; appears elongated and aligned with the most effective wind direction |
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what materials can be transported worldwide? |
• Atmospheric circulation can transport fine material such as volcanic debris, fire soot and smoke and dust world wide within days
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saltation (eolian) |
describes wind transportation of grains, usually larger than 0.2mm along the ground• About 80% of wind transport of particles is accomplished by this skipping and bouncing action; executed by aerodynamic lift, elastic bounce and impact
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surface creep |
grains hit other grains and knock them into the air, saltating particles crash into other particles knocking them both loose and foward |
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dine |
wind sculpted accumulation of sand |
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3 classifications of dunes |
1. Crescentic (crescent/ curve shaped) 2. Linear (straight form) 3. Star dunes
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loess |
fine grained clays and silts; its binding strength and its internal coherence, loess weathers adn erodes into steep bluffs or vertical faces |
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alluvial fan |
• Fan is produced whenever flowing water abruptly loses velocity as it leaves the constricted channel of the canyon of whenever the stream gradient suddenly decreases and therefore drops layer upon layer of sediment along the base of the mountain block
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bajada |
continuous apron of coalesced alluvial fans, formed along the case of mountains in arid climates, presents a gently rolling surface from fan to fan
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desertification |
unwanted expansion of deserted because the area will no longer sustain agricultural activity once its soils are gone; Occurs due to poor agricultural practices, improper soil moisture management, erosion and salinization, deforestation and global climate change
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