Ch 6a: Hydrosphere Flashcards
Define hydrologic cycle
Natural cycle of water movement at or near the surface of the Earth
Energy from gas to liquid
energy is released
Energy from liquid to gas
energy absorbed
Melting & Freezing do not take as much energy as
Phase change from liquid to gas
Define Latent heat
Amount of energy that is locked up in the system during phase change
Phase Change either
requires energy or lose energy
Characteristic of Water
bond mainly covalent but electron spend more time near oxygen due to polarity
Water is what kind of fluid
miscible fluid: excellent solvent for ionic and polar substances
Surface water:
rivers, lakes
Surface water is the ____ of the reservoirs
smallest but most visible
Surface water is a major
modifier of the landscape, largest natural movement of matter and sediments. Used to build deltas
Un-channeled flow is
overland or sheet flow
Channeled flow is
streams
River Systems:
streams are organized in river systems, tributaries typically merge downstream.
Define tributaries
river or stream flowing into a larger river or lake
Drainage basin:
area drained by a major river, separated by drainage divides
Drainage Styles depends on…
depends on topography and geology of the drainage area
Drainage Styles:
Dendritic, radial, rectangular, trellis
Drainage styles: dendritic
tree-like branching pattern, typical of terrains with uniform bedrock, stratified sedimentary or massive rocks
Drainage styles: radial
radial pattern, away from a central high point. eg. volcano
Drainage styles: rectangular
Follows 2 directions, at right angles, mimics pre-existing fractures of joint sets in bedrock, not much sedimentary rock
Drainage styles: Trellis
parallel stream systems, develop in valley and ridge terrain
Distributary
referred to as channels, root like
Characteristics of stream flow:
streams show variability in
gradient, velocity, discharge
Stream Flow Char: Velocity
velocity of flow varies within channel, slowest at base and sides, viscous drag
Stream Flow Char: Discharge
Volume of water passing a given point in unit time. Q = A* Vavg
Stream Flow Char: Gradient
Gradient decreases, steeper at the beginning and shallows out at the bottom
Sediment Transport
Competence and capacity of the stream depends on fluid velocity.
Methods of sediment movement
suspension, rolling and sliding on the bed (creep), saltation
Load types:
suspended load, bed load, dissolved load
Load types: suspended load
mainly silts and clays, some saltation of sand. will flow
Load types: bed load
coarsest material, movement through creep, traction or saltation
Load types: dissolved load
suspension, ions in solution
Downstream variation in sediment
net effect: downstream fining.
Downstream variation in sediment: suspended load
deposited when velocity drops
Downstream variation in sediment: dissolved load
typically carried to sea and precipitated out. eg. limestone or salt. Deposited as non-clastic sediment
what are Channel Patterns, and what do the types depends on
typically carve V-shaped valleys, the type depends on the channel shape and number of internal channels
Channel Patterns types:
straight, braided, meandering, anatastomosing
Channel Patterns: straight
single channels with low sinuosity. Characteristic of: young streams, areas with steep gradients
Channel Patterns: Braided
several small channels that join, low sinuosity, channels separate by islands or river bars of coarse materials
Channel Patterns: anastomosing
similar to braided, multiple channels within a larger channel, gradient is low, lots of finer sediments, lots of vegetation, steep, stable sides
Channel patterns: meandering
single channels, high sinuosity, older streams and areas with low gradients, sediment supply low to moderate and fine grained
Meandering migration
meander loops migrate downstream, highest velocity at the outside of the curve, lower velocity on the inside. Sinuosity increases with time
Meander loops: outside of the curve
higher velocity leads to erosion (cutbanks, thalwegs)
Meander loops: inside of the curve
lowest velocity leads to deposition (point bars)
Floodplain
typically alternating beds of silt and clay, grain size decreases away from the channel. bigger pieces of sediment rests near the edge
Flooding rivers
occurs when river level exceeds the channel banks
Terraces
former floodplains, pair or unpaired, result of stream incision and regional uplift
Alluvial Fans
Large, fan-shaped accumulations. Along the flank of a mountain, drier climates, form when channel opens into a valley or plain
Deltas
roughly triangular shaped deposits, form when a stream enters a standing body of water (Ocean/Lake). River may become divided into distributaries
Lakes
Standing bodies of water, many ways to form them. In general, an obstacle to flow is necessary. Most are geologically short-lived.
Open Lakes
inlet and outlet streams, water level tends to stay constant in short term, sediments are typically muds, with sands near shore
Closed Lakes
no stream outlet, water level fluctuates due to evaporation, sediments typically include salt deposits formed by evaporation
Ground water
groundwater: free water in pore spaces within solid earth. Probably less than 1% of Earth’s water. Total amount uncertain especially at depth
Water table: Vadose Zone
Unsaturated sediment, overlies the water table, gravity driven
Water table: Phreatic Zone
saturated sediments, pressure driver
Porosity:
amount of empty space within a rock or sediment, usually expressed as % by volume.
Permeabiltiy
measure of the ease with which fluid can flow through a rock, depends on: porosity, size of pore spaces, connectedness of pores
Aquifier
permeable unit with moderate to high flow rates
Aquitard
retards or slows water flow, flow rate depends on permeability and porosity
Springs
When the water table intersects the slope
Karst Topography
unique landscape found in areas with limestone. Chemical weathering turns in solutions
Stalactites are
on top
Stalagmites are
on ground
Distribution of snow
annual snow line marks boundary of areas that have snow year-round.
Properties of Ice
water expands as it freezes. An unusual mineral, open crystal lattice, lower density than liquid form.
Glacier (glacial ice)
land-based, mass of ice and snow. Normally moves down hill, survives from year to year, covers about 10% of the Earth’s surface, major modifier of the land surface. A lot of debris in glacier ice.
Glaciers are classified by:
location, size and shape, basal properties
Alpine
valley glaciers, ice accumulated in mountain valleys, may produce icebergs (calving) in water. eg. Cirque Glacier, melts –> tern
Continental Glaciers
huge masses, slow moving, very thick ice, radial movement, not confined to valleys, aka ice sheets and ice caps. eg. Antarctica ice sheets, 90% of the world’s ice, thick 3000m, 35 ma old
Transformation of snow to ice
snow flakes buried by successive snowfall. Summer melting (neve) pressure of the overlying snow, if the snow survives summer melting, further burial. Further compaction. Snow - granular ice - glacial ice (must be over a year).
Glaciers act as
environmental records
ice is typically finely layered; clean ice layers …
clean ice layers represent winter snowfall, dusty layers represent relatively dry summer
Ice also traps atmosphere gases, pollen
environmental records, internal structure of glaciers: temperature profile
Polar Glacier:
below freezing point throughout
Temperature Glacier:
temperate glacier is close to freezing point and has liquid water at base
Glacier Growth
glaciers are always growing and moving, glacial budgets.
Glacier appearance depends on:
accumulation, ablation
Accumulation:
addition of mass to a glacier
Ablation:
removal of mass from a glacier: melting, sublimation, iceberg calving, wind erosion. Above equilibrium line: more accumulation. Below equilibrium line: more ablation.
Glacial Flow Mechanisms
ice crystals deform under stress, continued deformation produces alignment. Plastic flow
Plastic Flow:
ductile, mobile, material acts like asthenosphere lower down, brittle at top like lithosphere.
Basal Slip
sliding of a glacier along its base, presence of water. The more water at the base, the faster it can move.
Basal ice temperature
Above the ‘pressure melting point’ of ice.
If the speed of a glacier increases…
it indicates something about the stability
Flow rates within glacier
Flow is fastest in upper center, slowest at edges.
Flow rates: temperate glacier
plastic flow and basal slip. Temperate = bottom is moving added flow from the top
Flow rates: polar glaciers
Frozen onto bedrock, no basal slip. Moves like staircases throughout layers. Fastest speeds at 2/3 from the base and in the middle of the channel.
Lakes beneath ice
Antarctica 1996, Lake Vostok, 200 km long, 14000 km^2
Crevasses form from:
Movement around or over obstacles: stresses the ice, forms crevasses. Most ice moves by plastic flow, upper 50m does not.
Surging Glaciers
typical of temperate (warm) and valley. Movement is downhill, rate of movement varies. Surges are sudden increases in speed.
Ice as an agent of change
Eroding and breaking up material, transporting it.
Erosions and Landforms: erosion
Debris laden ice erodes through: abrasion, attrition.
Erosions and Landforms: rock flour
can be blown around as dust (loess: wind blown silt) washed down into lakes.
Flutes:
ridge, backwards grooves: can be erosional or depositional
Grooves:
polished striations
Striations:
Tells directions
Horns formed from:
3 more aretes
Aretes:
thin ridges (cirque glacier)
Generic definitions (nongenetic)
descriptive
Genetic definitions:
specific
Deposition can be deposited from:
ice, by meltwater, proximal in glacial lakes
Sedimentation directly from ice:
till/diamict, moraines, erratics
Diamict:
nongenetic term, unconsolidated, poorly sorted sediments
Till:
Genetic term, specific on how it formed, deposited by ice with little or no reworking by water
Terminal Moraine:
furtherest end moraine
Lateral Moraine:
only exist in mountain glacier, material off to the side, can only be mapped when the ice is still there.
Erratics:
left over boulders from glaciers
Drumlins
Teardrop shaped hill indicating direction of glacial movement
Waterlain Deposits:
can occur on top, within or beneath the glacier as the glacier is melting.
Waterlain deposits: typical landforms
outwash plain, eskers, crevasse fillings, kames(&kettles), stagnation moraine.
Eskers:
long, narrow, sinuous ridges. Mainly composed of sand and gravel
Kames:
Conical hills or sand or gravel deposited on or adjacent to glacial ice
Kettles:
ponds or depressions left by melting masses of glacial ice
Glacial Lake examples:
Lake Agassiz, Lake Edmonton
Glacial lake sediments:
sorting increases away from the ice contact: ice rafted debris, debris flows, varves
Zones of sea ice
Perennial vs seasonal ice zones
Movement of sea ice:
typically moves several km per day.
Sea ice may..
May crack producing leads of open water.
Leads may …
freeze to make a complex mosaic.
Convergence of ice masses produces:
pressure ridges
Polynyas
large openings in sea ice
Global significance of sea ice: ocean circulation
salt extrusion as sea ice freezes: cold salty water is denser, flows down into deep ocean basins driving deep ocean circulation
Global significance of sea ice: global climate
sea ice has a high albedo: reflects light and heat, contributes to coldness of arctic regions
Permafrost:
covers 50% of canada, 25% of the Earth’s land surface.
Permafrost: active layer
Active layer: upper layer of soil that thaws every year.
Permafrost information:
restrictive in terms of climate, northern and alpine region, 1500 m thick in Siberia, 1000 m thick in Canadian arctic.
Define Permafrost:
soil or rock that remains at or below 0degress for at least 2 years –> frozen.
