Exam 2 Flashcards
When elemental iron (Fe) is exposed to oxygen (O2), what type of chemical weathering takes place?
Oxidation
Which of the following is Not a good method for mitigating soil erosion?
Repeated tilling
Standard Pedalfer soil
O - Organic layer A - Mineral Rich E - Leeched soil B - Clay accumulation C - Partially altered parent
Which type of soil has a thicker O-horizon; Histosols (wetland soils) or Laterite (Tropical rainforest soils)?
Histosols
Which of the following minerals is most stable at surface Earth conditions?
Quartz
What variables are needed to calculate the discharge of a river?
Width, depth, velocity
Which type of river is commonly found emerging from the toe of a glacier?
Braided river
What river is dominated by tidal forces?
The Fly River delta
What immense lake emptied in a catastrophic flood 15,000 years ago when an ice dam failed creating the Scablands?
Lake Missoula
Soils
Unconsolidated material capable of supporting plant growth
Regolith
Unconsolidated material incapable of support growth
Mechanical Weathering
Physical break-up of rock without changing the chemical composition; increases surface area and makes it susceptible to chemical weathering in the future.
Examples: Abrasion, frost-wedging
Chemical Weathering
Breaks down material via reaction with water, acid, gas
Pedalfer soil
Temperate, Fa-Al rich substrate, more leeching
Pedocal soil
Arid, Ca-rich substrate, little leeching
Laterite soil
Tropical, Fe-Al rich substrate, extensive leeching
Soil colors
Black = Organic rich Red/orange = mineral rich
Top soil attributes
Permeable, nutrient-rich, retains moisture, soft
What causes soil to lose fertility?
Repeated tilling, clearing of natural vegetation, failed crops, too much grazing
Drainage Basin (Watershed)
The source region from which a stream draws its water
Divide
Ridge or crest that separates drainage basins from one another
Runoff
Precipitation that moves across the ground to enter streams
Infiltration/Percolation
Absorption and movement of precipitation or surface water into groundwater
Headwaters
Where streams begin
Base Level
Endpoint of a river of stream
Thalweg
Fastest part of the stream
Gradient
Rise over run. The gradient is typically the steepest near the headwaters and the shallowest towards base level.
Traction Load (Bed Load)
Heavy debris rolled, pushed or dragged across the stream floor
Suspended Load
material suspended by turbulence of the stream
Dissolved Load
Material completely dissolved
Progradation
The river deposits sediments faster than the sea is able to remove them, so the delta grows outwards into the sea
Aggradation
The river deposits build up via overbank flooding, accumulation of biotic remains, etc. so the delta grows upwards
Transgression
The retreat of the delta, usually by the loss of sediments caused by continued wave attack or the reduction of nourishment soils
Point Bar
Stream velocity slows down around curves, deposits sediments
Cut Bank
Stream velocity is greater around the outside of a curve, so erosion is greater
Meandering Streams
Lower energy / velocity
Meanders tend to grow in size and migrate downstream
Can change >100m / year!
What causes sea level rise?
Glaciers are melting, adding water to oceanic basin.
Thermal expansion - warm things take up greater volume
Gravitational pull of glacial mass
Isostaty
Gravitational equilibrium between the lithosphere and asthenosphere.
Principle of Buoyancy
An object will sink so that the mass of displaced fluid is equal to the mass of the object.
Consequences of rapid sea level rise
Increased storm damage Increased coastal erosion Salinization of wetlands and aquifers Loss of marine habitats Displacement of human populations
Wave Refraction
Wind produces waves oblique to beach face.
Shallowing slows leading end
Waves bend as trailing edge travels faster
On irregular shorelines refraction acts to concentrate waves energy at headlands; facilitates erosion.
Hard Stabilization
Seawalls & Revetments
Groins
Breakwaters
Jetties - Form sandbars
Soft Stabilization
Beach nourishment
Land-use Restrictions
No build zones
“Strategic retreat”
Thermal Categories
Used to classify glaciers; determined by climate.
Temperate glaciers – Ice is at or near melting temperature.
Polar glaciers – Ice is well below melting temperature.
Wet-bottom glaciers
Water flows along base of glacier.
Basal sliding – Ice slips over a meltwater/sediment slurry.
Dry-bottom glaciers
Cold base is frozen to substrate.
Movement is by internal plastic deformation of ice.
How do glaciers move?
Highest velocities on the top and in the middle; crevasses form at the top of glaciers since it’s moving the fastest
Lowest velocities on the bottom and on the sides due to friction
Sea Level
Ice ages cause sea level to rise and fall.
Water is stored on land during an ice age – sea level falls.
Deglaciation returns water the oceans – sea level rises.
Sea level was ~ 100 m lower during the Wisconsinan.
If ice sheets melted, coastal regions would be flooded.
Dendritic Patterns
River flows over homogeneous landscape and water makes trunk streams (looks like a tree)
Radial Patterns
Precipitation runs away in all directions
Rectangular patterns
Crust broken up along parallel fault lines and rivers follow them
Ephemeral Streams
Water table drops below channel
Capacity
Willingness to transport more material.
Silty river = at capacity
At capacity = aggrading
Alluvium
River deposited sediments in a valley
Stream shape related to type
Soft sediments = slumps, L shape
Hard = Steep-sided canyons
Deltas
When rivers reach base level and velocity = 0, a delta is formed.
Isostatic Rebound
Happens due to removal of ice, or erosion/uplift
Wave-cut Platform
Steep edges/steps show historical coastline; land rising
Why is the ocean warmest around the equator, and coolest around the poles?
Due to salinity. Low amounts of ocean salt in the pole areas, and at the equator,
Thermohaline Circulation
Warm water at surface is fresh, and as it cools off, becomes salty and drops down due to increased mass
Lunar Pull
Gravitation pull of moon
Why do we have two tides a day?
Centrifugal force; Earth spins and pushes water out opposite side of moon. The sun also affects tides
Sun + moon = Spring tide
Tidal Flats
Sea retreats
Ebb Tidal Delta
Outgoing tidal flow is stronger than incoming
Flood Tidal Delta
Flood-dominated since tide is strong, comes in to deposit sediments, and weak outgoing tide cannot get rid of them
Undercutting
Wave smacking into tall cliff can cause it to retreat
Longshore Drift
Wave activity moving things downshore
Barrier Islands
Very delicate; require stable sea level
Beach Sediments
Sediments dumped by rivers at sea shore, collapse of cliff faces, wind, glacial melting
Erratics
Large, non-local rocks
Conditions to form a glacier
Cold climate
Snow has to be abundant
Snow must not be removed by avalanches or winds
Types of glaciers
Mountains glaciers - found due to high altitude
Continental glaciers - Found due to high latitude
Surging Glacier
Fast-moving glacier; can move meters per week. Caused by thinning and leads to crevassing
Parts of glacier
Zone of accumulation - year-round snow
Zone of ablation - seasonal snow
Equilibrium line separates these.
If accumulation > ablation, glacial toe advances and equilibrium line lowers.
If accumulation < ablation, toe will retreat upslope
Glacial Outwash Plates
Dominated by braided rivers due to high sediment load
Kettle Lakes
Retreating glacier drops off chunks of ice that melt and create depressions
Drumlins
Piles of sediments that form under glaciers
Eskers
When a glacier drains, one outflow location becomes preferred and leaves behind pile of sediment
