Exam 2 Study Guide - Physical Geography: Land and Water Surfaces | GEOG 2051, Study notes of Geography

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WATER RESOURCES
97%- Salt water (Saline)
3%- fresh  22%- groundwater o ½ deep o ½ shallow  77.8%- ice (glaciers and ice sheets)  0.2%- rivers, lakes, atmosphere, clouds, soil

Hydrologic cycle  Movement- getting water from one place to another o Vertical- up and down, precipitation, lifting o Horizontal- sideways, runoff, flow of water in the ground or rivers o Advection (movement of water vapor)  Reservoirs- places of water storages o Oceans, lakes, rivers, soil, ice sheets, clouds (biosphere), glacial ice, living organisms  Residence time- amount of time that water spends in a reservoir
-atmosphere = days
-river = few weeks
-groundwater = centuries, thousands of years

Global budget/balance  Matter cannot be created or destroyed  Whatever goes in must be balanced by what goes out  Budget: input = output

Groundwater- below the surface of the soil, more fragile than surface water reservoirs and easier to contaminate  Supplies about 20% of water in U.S.  Aquifer: body of porous rock that water can flow in and out of, container to hold ground water o Unconfined- ground surface above is basically flat and open at the surface allowing water to drain down(higher recharge rates and can make more intended use) o Confined- only a small area where the precipitation is allowed to seep down into the aquifer, has an aquiclude under surface and recharge rate is very slow, little o Saturated Zone- Lower portion in aquifer where the porous spaces are filled with water o Zone of Aeration- upper portion of aquifer above the water table where the porous spaces are filled with air o Water Table- top, upper most part of the saturated zone  Aquiclude- body of rock that doesn’t allow water to penetrate, helps store groundwater  Recharge Rate- rate at which water is input into our system (to the aquifer by precipitation), actually determines how much water we can make use of  Rate of Water Movement o Groundwater movement is much slower depending on how porous the material. o The various slow rate of movement can cause a number of problems o Contaminants cannot move around and are left in large concentrations  Cone of Depression  Some of the water can flow through the uppermost layers of the ground and make it into a net pathway;  The portion of water that infiltrates down in the ground and flows through the soil to the nearest channel

Groundwater-  Water that trickles down even deeper  This water may also ultimately make it into a channel  Provides base flow to many rivers with its consistent long term input of water

Drainage Patterns  Dendritic o Tree-like, most energy efficient b/c it allows the river cover area with smallest length of channel meaning there will be least friction slowing river down as it moves through;  More hilly terrain, less consistency in which direction is down  Parallel o Channels are all oriented in the same directions o Water always flows downhill which means its topography has steep slopes o Develops in areas with very steep, consistent slopes of land  Radial o Direction is flowing out from the center o Topography: Mountain, volcano, areas of high elevation  Trellis o Number of main panels with smaller tributaries flowing off of them o Parallel hills, series of rigid hills and valleys, Folded topography, smaller tributaries draining down into valleys o Stream capture: Water that was originally flowing down one valley has been diverted into another valley through erosion  Deranged o Water flow is very random, in many directions o Form in areas where the landscape has been recently disturbed (ex. areas that have been recently glaciated)
Flow in Channels  Meltwater (occurs in the spring)  Storms (can be seasonal input)  Groundwater (persistent, base flow)
Flow Regimes  Perennial Regime o Water flows into it all the time (ex. Mississippi River)  Intermittent Regime o Water only flows for part of the year (ex. Southern Cal)  Ephemeral Regime o Water flows in occasional (once every few years/decades) o Extremely arid regions
Discharge  The volume of water moving through a river per unit of time  Water is in form of a rectangle and discharge depends on volume of the box  Q (discharge) = W x D x V (water velocity - how fast the water is flowing)  Will have more discharge at the base of the drainage basin  Will have less at the head of the basin  Q almost always increases as you move downstream (more area)  The W, D, and V will get larger which makes Q larger
Exotic Streams  Streams in which discharge decreases as you move downstream  Water is removed through evaporation or human activity  Colorado River, Nile River
Sediment transport  River streams also carry huge quantities of sediment through running water
Divide into 3 components  Erosion o Refers to picking up the material  Translocation o Refers to moving particles from one place to another  Deposition o When the particles are deposited
Capacity  The total amount of sediment a river can transport
Competence  The largest grain size that a river is able to transport  Headwaters close to the drainage divide have a relative steep gradient o Longitudinal Profile  The key element of equilibrium in river systems  Rivers try to adjust their longitudinal profile so that their capacity to transport sediment is equal to the input of sediment  Depositing more sediment causes the profile to get steeper which increase the water velocity which increases capacity flow – equilibrium  Graded stream o Stream that is in equilibrium o Transport capacity is just large enough to transport out all of the materials supplied to the river o To have an entire river system that is a graded stream is very rare in nature b/c of the dynamics of the 2 variables involved  Inputs of sediment  Transport capacity o If the water is flowing too fast it will start to erode material into its bed which causes the profile to become less steep  Gravitational Potential Energy/ Energy of position o When a raindrop falls near the drainage divide it has this o Gets converted into kinetic energy (motion energy) that can move sediments o How much energy a river has depends on elevation difference between headwaters and base level (elevation of the mouth) o River’s ability to transport sediment is going to the be the difference in elevation o Elevation can change (sea level could fall/rise)  Stream Rejuvenation o Any way to knock stream out of equilibrium and stream is down-cutted into drainage basin  Entrenched meanders o Meanders than have been carved down into the bedrock o Tremendous amount of uplifting which adds energy to the river flowing process which causes downcutting o Ex. Colorado Plateau  Alluvial Terraces o Terrace: Series of steps running of the side of the valley o Alluvial: Made up of sediments deposited by rivers o Gone through a series of down cutting where material cuts away all of the material in the ground and starts migrating to other parts of the plain and starts cutting out material over there o Then there is another period of down cutting and horizontal migration takes over and enters a period of equilibrium and creates a new terrace  Nickpoints o Small little bumps that are scattered o Resistant outcrop, waterfall o Occur in drainage basin at places where river flows across nonresistant material o Location where we find waterfalls in river system o Over time rivers try to remove nickpoints by wearing away these materials. Tend to form a little cave in back of the waterfall. (occurs in all waterfalls). The cave will get larger and larger until it cant support itself and comes crashing down. The process begins over again with a new cave. Each time the nickpoint gets higher until it disappears and there is a smooth profile o Ex. Niagara Falls o Niagara escarpment creates the nickpoint in the drainage basin
Deltas  Depositional features that are created at the mouth of the river as it deposits the sediments that have been collecting in entire drainage basin and carrying through its course. Where river enters ocean it reaches a huge channel  Water velocity drops immediately at the mouth and reduces competence of river to deposit material  Many are rectangular shaped but can take on a variety of shapes depending on major process acting on it
3 major processes  Sediment supply (from the river) o More sediment = larger delta o Most dominant process o Ex. Mississippi River  Wave Activity o Waves will pick up all of the material and plaster it along the shoreline o In wave dominated deltas you end up with a more triangular shape with distributaries (smaller channels that supply water to a channel) flowing into the main channel. Will end up with extensive beaches stretching along the mouth of the river.  Tides (tidal currents) o Some basic wave of land, but the delta is divided into smaller islands leaving larger channels to carry the tidal flow in them Flooding
Hydrograph  Represents flood flows, discharge through time  Discharge on vertical axis, time on the horizontal axis  Base flow = Lower level of flow  Lag time = time in between the precipitation and discharge peak  Bump in discharge is excess flow 
Drainage Basin Characteristics
Size  Bigger drainage basin = more water collected = increased peak discharge and lag time (gives us more time to prepare)
Vegetation
Low vegetation, lots of sand
Agricultural Areas
Typically left unvegetated for a period of the year
Wind erosion can be very significant, wind plays a very imp. role
Loess Regions
Loess = Fine grain material (silt sized) which largely originated during glacial events
Large deposits in Mid West, Europe, China
Grain is the single most important food substance

Aeolian Transport of Sediments
Sediment transport by wind is much like transport by running water
Modes/Types of Sediment Transport
Suspension
Particles flow in the wind
Bedload Transport
Material that remains in contact with the ground during transportation
Saltation
Particles bouncing along the ground
Creep
Largest particles rolling along the bed
No Solution Mode of transport like running water
Density
Air is 1000X less dense than water
Erosion
Two distinct mechanisms of erosion
1) Deflation
A lowering of the surface caused by the removal of fine materials
Desert pavement (a result of deflation)
Layer of coarse material (pebbles, rocks) covering the surface
Start with mixture of large and fine rocks wind blows across surface and can only remove the dust like particles which only leaves a concentration of larger pebbles  surface is lowered and creates a desert pavement where wind is no longer effective
Blowouts (another result of deflation)
Compressions (bowl-shaped/circular or long/linear) that are created where the wind has been able to deflate the surface
Common in coastal areas
2) Abrasion
sand blasts, sand grains are relatively sharp that when rubbed against an area tend to wear down the surface that it comes in contact with
Ventifacts
Angular rocks that have one or more facets (flat sides) that result from abrasion
Yardangs
Can be eroded into rock outcrops or carved into weaker unconsolidated material
Streamline form created by abrasion to allow the wind to slip around the obstruction with the least amount of friction and interaction
Deposition
Sand dunes
The best known features created by the work of the wind, can come in a wide range of shapes
Deposits of sand created by Aeolian transport
2 categories of dunes:
Fixed Dunes
Mobile Dunes
Dune migration tend to be relatively slow (10m/year)
Slipface = usually built up to the angle of repose
Stoss slope = windward slope up the dune
2 factors that control the type of sand dune
Availability of sediment
with more sediment, can build larger dunes
Winds directional variability
Types of Sand Dunes
Barchans
Crescentic shaped dunes
The horns point down wind
Tend to form in areas with very small sediment supply
Only form in areas with unidirectional winds
Barchanoid Ridge
Sinuous crested ridge that meanders back and forth
Ridge crest line is oriented perpendicular/transverse to the wind direction
Ephemeral Streams
Dry stream beds, water only flows in occasionally
Arroyos, washes, wadi
Surprising number of people drown in these areas
Playa
Temporary lakes, broad, shallow area
Ex. Owens dry lake, badwater
Alluvial Fan
Fan shaped/cone shaped deposit of sediment that is created where an ephemeral stream runs out of the valley floor
Will deposit material in one area for a while then shift to another area back and forth over time which creates a cone/fan shaped pile of debris
Essentially a delta on land
Common in SW
Bajada = coalesced alluvial fans, group of alluvial fans that have grown together to form a continuous group of sediment that runs up the valley floor t
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Coasts
The most significant of all geomorphic environments:
Population
Roughly 2/3 of worlds population live in coastal areas
Economic
Lots of things going on – recreation, fishing, tourism, oil and gas, etc
Tremendous amount of infrastructure supporting these activities
Dynamic
Coasts are very dynamic (rapidly changing)
Tremendous amount of energy (storms, waves, tidal flows)
Young
From a geologic standpoint coasts are very young environments
Further out of equilibrium which causes more change

Littoral Zone
Area where sediment is movement around by marine processes on a regular basis
Water Zones
Offshore
Not part of the littoral zone
Nearshore
Where the littoral zone begins
10m water depth
Surf Zone
Move landward from the nearshore
Area where waves peak up and then break crashing down
Under low energy levels (MS) waves break right on the shore, very narrow surface
Swash Zone
Landward most edge of the water
Swash is the water that rushes up the beach every time a wave hits
Land Zones
Foreshore
Seaward most land zone
Area between high and low tide
High tide –foreshore covered with water
Low tide – foreshore is fully exposed
As the tide goes up and down it moves back and forth along the foreshore
Beach/Berm
Landward of foreshore
Flat portion of the beach
Backshore
Landward of the beach/berm
Includes sand dunes, cliffs
Difference in height between the crest and trough
Difference between 2 successive wave troughs or wave crests
Height of the wave determines how much energy a wave has
Higher wave – more energy and more work it can do
Lower wave = less energy and less work it can do
Wave Steepness = height/length (height divided by length)
Influences direction of sediment movement underneath waves
Low steepness push sediment on shore
Steep waves push sediment off shore to cause erosion
Wave speed (in terms of Wave Period)
The waves period is the amount of time it takes for a wave to travel one wavelength
Typical periods for ocean waves would range from 2-3 sec (very low waves) to as much as 25 sec (very long waves)
Waves carry tremendous amounts of energy
Power source of waves
Wind (solar energy) and Sun (solar heat)
Wave generation = the creation of waves
3 basic factors that control the nature of the waves
Wind speed
Faster the wind- the bigger the wave, more friction
Duration
Longer the wind blows –larger the wave
Fetch
Refers to the distance of open water that is available for wind to blow across
When wind crosses along the water surface it creates a circle, the diameter is the distance across the surface which is equivalent to the wave height
As you go deeper in the water the diameter of these orbits get smaller
Time it takes for water particles to go through a wave orbit is the same as the wave period
Wave Base
Depth is roughly 1/2 of wavelength (bottom of the wave), in shallow water
Shallow depth shortens wavelength
The wave is in shallow water when it begins to come in contact with the bottom of the ocean and can move sediment around
Wave Shoaling (many changes begin to occur)
Wave enters shallow water, particles spinning in circular orbits below it, orbits are interacting with the bottom creating energy and this slows the wave down
1st shoaling stage- is the length of wave begins to decrease
2nd - When the length is decreased, the water in the wave will pile up which increases the wave height
Steepness = height/length
increase in height and decrease in length cause steepness to increase
These processes will continue until we reach a point where the wave gets so steep that it is no longer stable and it will break and crash
3rd stage – wave break
Wave period is the only process that doesn’t change (remains constant)
Phenomena caused by wave shoaling
Wave refraction
wave crests bending and changing direction that results from different portions of being in different water depths and moving at different speeds
Wave refraction – shoreline straightening
Bay areas have very low energy levels & wave heights
High energy at the headlands - large waves are crashing into the rocks which creates erosion
Overtime the shoreline will tend to get smoothed out b/c headlands are eroded and embankments are filled in
(A)Longshore Current
Caused by waves approaching the shoreline at an angle (angle of incidence)
Waves start moving sediments around creating currents
Water flows parallel to the shore and if the current is strong enough it will push sediment with it
Can subdivide the wave energy into 2 directions
Portion of the wave energy is directed in the onshore/offshore direction
Portion of the wave energy is directed in the longshore direction
Beach drift
Longshore transport of sediment along the foreshore, As 1 of these waves comes into coastline and it breaks and water rushes up beach, the waves come in on an angle
Tsunami
Generated by something that displaces the surface of the ocean for a relatively large area
2 basic mechanisms that drive tsunamis
Earthquakes
Very large scale submarine landslides
In deep water tsunamis move very fast
Height is very small, the wave length can be 100 km
Have very little impact and can be hard to notice
relatively long as the reach deep into the water
have a relatively low height, low steepness
net onshore currents which causes net onshore movement of sand on shore
The sand will begin to build up the foreshore area making it steeper which makes the backwash stronger
Eventually reach an equilibrium – all of the sediment washed up is washed back
Relatively wide beach with a steep foreshore
Storm Waves - Occur during stormy seasons
Tend to be shorter in wavelength, relatively high, lots of energy, very steep
Steep waves tend to push sediment in the offshore direction
Will begin to cut material away and carry it offshore and deposit the material in shallow water
End up with a narrower beach
Sand is stored temporarily creating a nearshore bar
Spits and Tombolos
Both examples of features that are created by longshore transport (when waves approach shoreline at an angle and net transport is going to move along the shoreline)
Spits
Ridges of sand that are built by longshore transport typically at location where the orientation of the shoreline suddenly changes
Tend to straighten out the overall shoreline orientation – when sudden change of shoreline the spit straightens it
Tombolos
Ridges of sand that form bridges that connect the main coastline to some obstruction in the nearshore zone
Barrier Islands
Long, linear islands comprised of sand that are separated from the mainland by relatively narrow, shallow bodies of water (lagoons, bays, sounds)
10-15% of worlds coastlines have them, common in Eastern Coast of US
Ocean Beach
Characterized by relatively high energy levels, fairly big waves, wider and more gently sloping beach that acts as a buffer for the wave energy
Foredune
Moving more landward from the beach you encounter vegetation
Very salt tolerant
Vegetation controls the position of this first dune
If sand is being added to the island (positive budget) sand will be deposited on the beach making it wider and the area near the ocean will be flooded less frequently and vegetation will be extended along the beach and less salinity level and overtime you grow a new foredune
This cuts off the supply of sediment to the original foredune
If there are large tress and much vegetation the barrier island is very stable
Bay side
Can find a number of environments
Bay side Beaches
Quite narrow and steep, very low energy environment
Tidal Flats
Flat, table-like deposits that extend out into the water
Salt Marshes
Will never find salt marshes on the ocean side b/c energy levels are too high
Barrier Island Rollover
The landward migration of a barrier island
Sediment is picked up from the ocean side of the land and is pushed over by wave activity to the landward side and whole island shifts over –peat soil builds up
Dune scarping
Result of wave erosion
Dunes get breached and sand starts to push through them
Or major storm comes and wipes out large sections of dune
Peat outcrop on the beach proves that there has been barrier island rollover
Peat cant form on ocean side and will only form on low energy protected landward side
Overwash Fan
Relatively large dune system (8-10 ft tall)
Shifts island in landward direction
Barrier Island Formation (many theories)
Spit extension
Barrier island forms as a result of a spit getting breached by a tidal inland
Reach a point when the spit gets so long and becomes hydro- dynamically inefficient
Get wave setup and blast through cutting breach through spit which leaves portion of spit detached from mainland called a barrier island
Drown-in-place
Water levels rise but shoreline isn’t able to migrate fast enough to keep up so it drowns in place

Biological Landforms
Living organisms play many roles in coastal landform development
Erosion in rocky coastlines, secrete gases to form rocks, create sediments through depositional environment
Coral Reefs