Final (Chapter 13-20) Flashcards
why do continents rise above oceans?
isostasy
what is isostasy?
buoyant continental lithosphere floats on dense asthenosphere
what is orogenesis?
mountain-building processes
what are the 3 plate boundaries?
divergent, passive, convergent
what are divergent continental margins?
mantle plume rises, uplifts and splits continental lithosphere to form rift valley with blocks dropped along normal faults, and volcanoes along valley sides
what are passive continental margins?
rift widens, seawater invades, and a new ocean basin forms whose sides experience no seismic activity but gradually subside under weight of sediment load
what are convergent continental margins? (2 types)
as mountains grow, undergo isostatic adjustments to balance weight
what are andean-type convergent margins?
oceanic crust subducts beneath continental, developing accretionary wedge, continental volcanic arc, and plutons in core of deformed mountain belt
what are aleutian-type convergent margins?
oceanic crust subducts under oceanic, to form volcanic island arc
what is continental collision? (convergent margins)
ocean basin closes, subduction stops, highest mountains form (continental crust cannot subduct under more continental crust therefore creates very high mountain *push eachother up*)
what are accreted terranes? (convergent margins)
foreign pieces of crust forefully attached to continental margin
what is the Wilson cycle?
oceans opened and closed, mountains built and rebuilt repeatedly; rarely pieces of oceanic crust got stuck onto continental margin during obduction
what is uplift? (broad vertical movements in continents)
by mantle upwelling pushing up continental lithosphere in continent interiors
what is subsidence?
how is it caused?
gradual sinking in or land
mainly due to weight of sediment deposited along passive continental margins as mountain belt erodes; also downward mantle flow pulling on lithosphere
what is the origin and evolution of continental crust?
formed by the combining of volcanic arcs above subduction zones
where is the earliest continental crust found today?
in shield areas of continental interiors
what is the main trigger of mass wasting? and what intensifies this trigger?
gravity: always pulling rock, regolith and soil down slopes….more effective if water saturates materials on slopes, reduces cohesion friction and adds weight
what causes oversteepened slopes?
due to undercutting by waves, streams, and human excavation, resulting in loss of support for materials higher up in the slope
how does removing vegetation trigger mass wasting?
vegetation anchors soil and regolith with plant roots; removing plants make the slope unstable and susceptible to failure
how do earthquakes trigger mass wasting?
can dislodge rock and unconsolidated material, resulting in landslides
how is mass wasting classified?
based on types of materials, types of motion (freefall, sliding and flowing) and how fast they move
what is slump mass wasting?
rotation of a block of slope material along a sliding surface (usually lubricated by water) gravity pulls the block in a rotational motion away from a scarp with the block’s surface tilting back - happens when they slop is undercut by a stream, by waves or by human excavation
what is rockslide mass wasting?
common where rock structures parrallel slopes (mountainous areas) provide sliding surface, or where stronger rock rests on weaker rock especially if the slope is undercut, sliding surface is lubricated after heavy rain or snowmelt, or shaken by an earthquake
what is debris flow?
fast flow of saturated soil and regolith down valleys following heavy rain OR during and after volcanic eruptions where ash gets mixed with melted snow and ice rushing down valleys (lahars)
what is earthflow?
slower movement of (mainly) mud down hillsides in humid areas following heavy rain or snowmelt; forms a tongue-shaped mass that may continue to move slowly for years; commonly starts as a slump
what is a creep?
gradual down-slope movement of soil and regolith under gravity; caused by repeated freezing and thawing, wetting and drying, or water saturation following heavy rain or snowmelt - results in tilted trees, fences and utility poles
what is solifluction?
flow in saturated ground resting on impermeable rock, clay or permafrost in polar areas; water cannot percolate downward below the impermeable surface and so material flows slowly downhill as lobes
what is the hydrologic cycle?
97% of earths water is stored in the oceans, evaporated then precipitated on land - some soaks in (infiltration) some flows over the land as streams (runoff), some evaporates back into the atmosphere and is transpired by plants, and some is stored in glaciers, but most returns to the oceans by streams
what is streamflow?
stream erodes, transports according to its veolcity and channel shape
what is gradient? (in relation streamflow)
slope of stream channel over its length; cross-sectional shape determines how much of the channel contacts water, slowing it down; rougher, more friction
what is discharge? (in relation to streamflow)
volume of water flowing through the stream’s cross-section per second; if discharge increases, stream usually gets wider, deeper, and faster downstream
streams _____, _____ and _____ simultaneously over their lengths
erode, transport and deposit
how do streams cause erosion?
by wearing down from particles in transport acting as cutting tools to scour channel walls (like sandblasting) and in circular eddies (circular movements of water) to cut potholes into the channel floor
what are the 3 types of sediment loads transported by streams?
dissolved : ions in solution from chemical weathering and groundwater
suspended : sediment that remains above the bed;
bed load : is particles sliding and rolling along the channel floor
saltation : involves jumping and skipping of particles that alternate between bed and suspended loads
what is deposition?
occurs when stream can no longer cary its load and particles fall to the bed; can form a channel deposit of sand and gravel in bars, or floodplain deposit of mud beyond the channel
what are stream valleys?
a stream cuts vertically but its bandks cave in by mass wasting to develop narrow V-shaped valleys with waterfalls and rapids in rough channels
where do wide valleys form?
on gentle gradients and cut mainly sideways forming flooplains as the stream shifts back and forth across the valely leaving a thick fill of sediment
what are drainage patterns determined by?
network of tributaries (river or stream flowing into a larger river of lake) feeding the stream
what does the pattern of a basin (large low-lying area) depend on?
rock types and structures
where do dendritic patterns of drainage occur?
uniform bedrock where channels follow local slopes
where do radial patterns of drainage occur?
from a volcano or rock dome
where do rectangular drainage patterns occur?
where stream flows over joints or a fault system with right angle bends
what are artificial levees? and why are they built? (in relation to flood control)
man-made wall built to keep water from going into certain areas and prevent flooding
built along stream banks to increase the volume the stream can hold
why are flood control dams built?
to store water then let it out slowly - resulting reservoirs are used for irrigatio, power generation
what are some of the downfalls of flood control dams?
flood river valleys, displace wildlife, drown forests, and fill with sediment that reduces their holding capacity and effectiveness
what is the most effective way of getting water underground?
steady rainfall soaking into the ground because heavy rain produces mostly runoff and little infiltration once plant requirements are met
what is the zone of saturation?
pores of sediment or rock are completely filled with water
what is the zone of aeration?
pores contain mainly air and minor water held as soil moisture
what is the water table? and what does it mimic?
the surface between the zone of saturation and the zone of aeration
mimics the land surface eg. the water table is highest under hills and lowest under valleys
what does the movement of ground water depend on?
nature of materials
what is porosity?
volume of open space in rocks or sediment, including fractures and openings
how is porosity reduced?
by pores getting filled with cement and fine particles
what is permeability?
connection of pore spaces and ability of material to transmit
what is impermeable material called?
aquitard
what is permeable material called?
aquifer
how does groundwater flow?
under gravity in a pattern of long curving paths towards streams
what are springs?
where water table meets the ground surface; springs may occur where an aquitard causes the local water table to be “perched” above the main water table
what are hot springs?
where groundwater is heated at depth then rises to the surface
what are geysers?
water boils under pressure, vaporizes and blasts water into the air, then water refills the pipe and cycle starts over again (old faithful erupts ever hour)
what are wells?
holes drilled into the zone of saturation; must be drilled deep enough below the water table to retrieve water during the dry season
what do wells cause?
cones of depression in the water table where it is drawn down toward the base of the well
what are artesian wells?
tap water under pressure in an aquifer that is sandwiched between aquitards; water naturally rises to the ground surfce with minimal pumping
what is subsidence?
pumping water for irrigation faster than it can be replenished causes underlying sediment to compact, resulting in gradual sinking of the ground surface
how does groundwater contamination happen?
from septic tanks, fertilizers, toxic spills, buried chemical tanks, and leaking sanitary landfills; polution can make its way into aquifers
where should cities dispose their waste and why?
in impermeably sites because it takes many years to flush out (cleanse) an aquifer
what is the geologic work of groundwater?
by solution of soluble rocks to form
what are caverns?
by groundwater solution enlarging cracks and bedding planes in soluble rocks just below the water table
how do needle-like stalactites (icicle-shaped formation that hangs from the ceiling of a cave) form?
by water dripping from cave ceilings
what are stalagmites?
upward-growing mound of mineral deposits (looks like a post)
what do stalactites and stalagmites eventually form?
columns (conjoin because of upward and downward growing)
what is karst topography?
is a landscape formed from the dissolution of soluble rocks such as limestone, dolomite, and gypsum
how can sinkholes develop in limestone terrains? and what disappears into them?
by solution and collapse of the ground surface; short streams
how do glaciers form?
by compaction, re-crystallization of snow that eventually turns into ice
what are ice-sheets?
type of glacier: radial-spreading large ice masses on continents (eg. Anartica)
what are valley mountains?
type of glacier: commonly flow down old stream valleys
what is the normal movement of glaciers?
cm per day
where does an upper brittle zone of fracture (approx 50m thick) usually ride?
on lower zone of plastic flow (glacier’s weight becomes too much to support itself)
the glacier may also ____ over its ____
slide, bed
what does budget of a glacier involve?
2 zones, accumulation; gain of snow or ice
ablation; wastage or loss by melting, evaporation, icebergs calving (split and shed) in water
if accumulation > ablation what happens?
the glacier’s terminus (end point) commonly advances
if accumulation < ablation what happens?
terminus (end point) usually retreats
where is internal movement always located within a glacier?
towards the front (even in retreat)
how does glacier erosion occur?
by plucking: freeze-on of loose bedrock
abrasion: using the glaciers load to scrape, scour, gogue the subglacial floor and sides
how do striations (scratches) and grooves form?
by particles in ice scraping over bedrock
what are glaciated valleys?
U-shaped valleys
what are cirques?
rock bowls at heads of valley glaciers, gnaw into a mountain divide from the sides
what are fjords?
U-shaped valleys along coasts
what are aretes and horns?
sharp mountain ridges and peaks
how are aretes (sharp ridges) and horns (pyramid-shaped peaks) formed?
form where multiple cirque glaciers gnaw into a mountain divide from the sides
what is glacial drift?
glacially-derived sediment
what are the 2 types of glacial drift? and when are they released?
till and stratified drift
both are released when the glacier ice melts
what are characteristics of till?
forms directly from glacier ice
contains a great variety of particle sizes
stones appear scratched, polished, and faceted from glacial transport
what are lateral moraines?
till built along the sides of valley glaciers
what are end moraines?
curved ridges at the glacier terminus where it piles debris by dumping and bulldozing (formed by till)
what is ground moraine?
plastered till beneath glaciers
what are drumlins?
mounds streamlined under the glacier (blunt ends point-up glacier)
what is stratified drift?
comprises sand and gravel deposited by glacial melt-water
what is the difference between till and stratified drift?
ice cannot sort the sediment it carries therefore it is comprised of unsorted particle sizes
what is stratified drift an excellent source of?
aggregate for building cities
what is a kettle? (associated with stratified drift)
a depression in the ground left by an ice block that melted there
what is a kame? (associated with stratified drift)
a debris mound lowered to the ground from the glacier surface as ice melted
what is an esker?
a winding gravel ridge commonly formed in a subglacial tunnel
what are causes of glaciers?
plate tectonics and continental drift bring a major continent over a pole, allowing glaciation to start (by inducing glogal cooling)
what are glaciations controlled by?
3 cycles related to earth’s orbit around the sun
when does a major glaciation happen?
when conditions combine for minimal contrast in seasons at mid to high latitudes, more snow falls during mild winters and less snow melts during cooler summers
what are deserts?
dry places where there is low precipitation and little vegetation
what is weathering? (referring to geologic processes in deserts)
almost entirely mechanical and very slow due to low precipitation; however clays and thin soils form by oxidation of ferromagnesium silicate minerals
what does most of the eroding of desert surfaces?
ephemeral streams and flash floods from short, intense rainstorms (especially erodes sediment not anchored by vegetation)
how does wind carry sediment farther and higher than streams?
wind can move faster than water
not confined to channels
what is a bedload?
sand moving by saltation (grain collisions) and rolling over the ground
what is a suspended load?
dust particles are pushed into the air by saltating sand grains, then swept up by the wind in dense clouds and carried high into the air
how does wind erosion occur?
by deflation and abrasion
what is the process of deflation?
blowing away fine sediment to create blowouts, while leaving coarser particles behind that cover the desert floor as desert pavements
what is the process of abrasion?
particles sand blast things mainly by saltation; wind polishes, pits and facets stones (ventifacts) setting on desert floor and streamlines ridges (yardangs)
when does wind deposition occur?
when the wind slows down and is no longer able to carry its sediment load (produces landforms made of sand and silt)
where are sand dunes formed?
in wind shadows around obstacles where the sand builds small mounds that induce more deposition (self-perpetuating)
describe characteristics of sand dunes
an unstable slip face forms on the leeward (downwind) side which is always steeper (approx 34 degrees) than the windward (upwind) side; the dune gradually migrates in the direction of the slip face on which primary cross-beds are deposited
what are barchan sand dunes?
type of sand dune
crescent-shaped with tips pointing downwind
where do barchan sand dunes form?
form where supplies of sand are limited and the ground surface is flat and lacking vegetation
what are transverse sand dunes?
series of ridges and troughs elongated perpendicular to wind direction
where do transverse sand dunes form?
commonly along coasts where wind is steady, sand abundant and little vegetation
what are longitudinal sand dunes?
elongated parallel to wind
where do longitudinal sand dunes form?
large deserts where sand is moderate
what are parabolic sand dunes?
crescent-shaped with tips pointing upwind and commonly anchored by vegetation
where do parabolic sand dunes form?
where lots of sand occurs along coasts and wind blows onshore
what is a loess?
blanket of outwash or till deposited over landscape from deflation of dust carried far from deserts or glacial deposits
loess makes ____ ______
fertile farmland
how are waves created?
from wind blowing over the ocean; a surface waveform of energy moves through the water whose molecules move side to side and up and down
what happens as a wave approaches the shore?
it “feels bottom” and breaks into surf that moves up a beach as swash then water flows back down as backwash
what do storm waves do?
erode headlands by wave impact compressing air in fractures, by abrasion, undercutting
what is wave refraction?
waves bend as they approach an irregular shoreline
what is beach drift?
zig-zag patern of swash and backwash from waves hitting the shore at an angle and moving sediment
what are longshore currents?
currents that flow parallel to the shore that are produced by oblique waves in the surf zone
what do longshore currents do?
move most of the sediment in transport that is supplied mainly by rivers
what do shoreline features depend on?
geology and wave activity
what are wave-cut cliffs?
wave-cut platform caused by collapse and retreat of cliff from cutting action of surf against the base of cliffs sweeping debris out to sea
what are arches?
where waves cut caves into the sides of headlands until the caves join; eventually arch collapses and leave a stack sitting along on the wave-cut platform
what do depositional features depend on?
sediment supply and current activity
what are spits?
elongated sand ridges that form where beach drift, longshore currents move sand into the mouths of bays
what is a bay-mouth bar?
where a ridge crosses the bay
what is a tombolo?
a sand ridge that connects an island to the mainland or another island
what do many coastlines start out as?
with an irregular shape as a series of headlands and bays
what straightens out shorelines?
continued cliff retreat and sand deposition
what are jetties used for?
to keep sand out of river mouths
what are groins used for?
lie perpendicular to the shore to trap sand and widen beaches
what do jetties and groins cause?
erosion on the down-drift side of the jetties and groins and forces neighbours to build more structures
what are breakwaters used for?
built parallel to the shore to protect marinas and beaches from storm waves
what do breakwaters tend to do?
widen the beach and fill in marinas
what are seawalls used for?
to protect shores from storm waves (walls must be maintained at high cost)
what are the downfalls of beach nourishment? (process of dumping or pumping sand from elsewhere onto an eroding shoreline)
requires alot of sand
very expensive
only lasts several years
requires continual maintenance (more sand and more money)
_______ of buildings is best along shorelines that get the worst storms, explain why
relocation, costs too much in money, materials and safety
non-metallic are _____ _____
industrial minerals
what are magmatic metallic mineral deposits
heavy crystals like chromite and magnetite can settle in colling pluton, lightest minerals with rare elements crystallize in pegmatite dykes (huge crystals)
what are hydrothermal metallic mineral deposits?
metals in hot solutions from magma precipitated as vein deposits of gold, silver in rock fractures
- disseminated deposits* of copper, molybdenum ore are spread throughout porphyritic host rock
- volcanogenic massive sulphide* deposits resulted from fresh seafloor reacting with hot water at ancient oceanic ridges
what are sedimentary metallic mineral deposits?
- banded iron formation* including magnetite, hematite, chert formed by bacteria in Precambrian seas when the atmosphere lacked oxygen
- placer deposits* formed by running water concentrating heavy minerals (golds, diamonds)
what are metamorphism metallic mineral deposits?
contact metamorphism and associated igneous activity cooked rocks including limestone that became skarns rich in zinc, lead, copper, and gold
what is weathering? (refering to metallic mineral deposits)
by hydrolysis of silicate minerals in the tropics; concentrated insoluble aluminum as an oxide (bauxite) that is shipped to Canada to extract the aluminum
what are non-metallic resources important to?
constrution, food and chemical industries
what is concrete and asphalt made from?
crushed stone, sand, gravel
what is cut stone used for? (eg. granite, gneiss, slate)
building facings, walkways, countertops
diamonds are mined for?
abrasives and gems
where do diamonds form?
deepest roots of old mountain belts, then picked up by rising bodies of kimberlite from asthenosphere
what are clays from silicate weathering used for?
bricks, sewer pipes, pottery, and chemical industry
what is calcite excavated for?
cement, asphalt, chemical industry
what are evaporite salts (like gypsum) used for?
plaster (drywall), salt for chemical and food industries, potash for fertilizer
where is phospate mined from? and what is it used for?
mined from sedimentary rocks
agriculture
where is sulphur extracted from?
coal, oil, gas
what are non-renewable energy resources?
fossil fuels whose use is hard on the environment
what is petroleum used for and where does it come from?
used for fuel and plastics
formed in ancient seas from remains of plankton that were buried, then progressively heated to kerogen, oil, natural gas (because oil, gas are lighter than water, migrate up into permeable reservoir rocks until they hit a petroleum trap where reservoir rocks meet impermeable cap rock)
what is coal used for and where is it formed?
used for fuel
formed from decayed land plants in ancient swamps that were buried compressed, then cooked to form coal; CANADA = big exporter
how is the oil extracted from heavy oil sands?
heated (Alberta- huge but viscous)
how is nuclear energy released?
by splitting uranium atoms (fission), uraninite is main ore
what are renewable fuel sources?
a couple of geologically-related alternatives to fossil fuels
what are benefits of hydroelectricity?
what are the cons?
damming streams gives clean energy, supplies most of Canada’s electricity
do not last forever, reservoirs fill with sediment, lose capacity
how does geothermal electricity work?
where heated groundwater and steam in volcanic area is tapped and piped to turbines that convert energy to electricity
not developed much in canada
