Chapter 15 and 16 Flashcards
mid-term review
Aeolian system
wind a general part
of the circulation of the atmosphere
What is the aeolian system driven by? In what sorts of places?
Driven by solar energy. Wind is an effective agent when vegetation is
scarce (arid, glacier, coastal)
Where does brittle fracture occur?
Arid environments where breakdown is primarily brittle fracture,
regolith tends to be stony, sand and silt-grade material.
Sediment movement
Air retarded by friction with ground.
* Boundary layer condition – air is not moving at the surface
* drag velocity U*
* critical threshold velocity: threshold at which sediment moves
entrainment of particles by wind occurs?
Balance between resisting and impelling forces
-variation in atmospheric pressure can depress or raise sea level (low pressure Hurricanes sea surges)
-creates the intertidal habitat to which a range of plant and animal organisms that are adapted and which have geomorphological effects
-with each tide an influx of nutrients are brought in
Resisting forces
inertia,
* friction,
* cohesion
Impelling forces
- drag force,
- lift force,
- ballistic impact
Waves
-wave action is probably the most important agent of coastal change
-wave is measured by the wavelength and height of the wave
-wind speed, duration of wind, and fetch determine wave height
-waves travel faster in open water
-waves travel slower in shallower water
saltation
process involving the movement/transportation of particles such as sand or soil by wind or water
-involves a bouncing or hopping motion where particles are lifted from the surface and then brought back down again, often to be lifted again
inertia
the tendency for objects at rest to remain at rest and for objects in motion to continue in motion unless acted upon by an outside force
-property that opposes attempts to put an object in motion or to change the magnitude or direction of its velocity
friction
the force that resists the sliding or rolling of one solid object over another
cohesion
describes particles that are the same tend to stick together
drag force
the force of wind or air resistance pushing in the opposite direction to the motion of the object (aerodynamics of a plane); friction caused by air, which opposes motion
lift force
the force exerted by moving air (wind) on a surface; acts in an upward direction in order to counter the force of gravity; a mechanical force generated by a solid object moving through a fluid
Erosion by wind
- Removal of surface sand – leaves behind stones – desert pavement or reg
- Wind faceted stones are called ventifacts
Aeolian deposition
process of dune formation
* Ripples
* Desert Dunes
* Coastal Dunes
Three types of currents
longitudinal, transverse, surface
nearshore dynamics
-waves transport sediment
-swash and backlash
swash and backwash
types of wave movement that influence the structure of a beach
swash
refers to waves traveling towards the beach, pushing sediment up the shoreline and contributing to coastal deposition.
backwash
the movement of water back down the beach and into the ocean, which scours out the beach and carries materials away
coastal erosion
if sediment removal>supply, then no beach and wave energy is directed at bedrock plus:
-salt weathering, marine organisms, water layer weathering…
costal deposition
-leaving beaches(whether there is more deposition than removal of materials), sand dunes, tidal flats, and estuaries
ripples
caused by the interaction of wind and water, or the physical interaction of the water with another object
coastal dunes
- An embryo foredune may form which traps further sand.
- Positive feedback during development
- Energy is absorbed, saltation declines and deposition occurs
- Inland migration of the dune mass, and new dune formation
- Vegetation stabilizes the dune
- When disturbed by humans or animal blow out can occur
coastal conclusion
-coastal processes are dominated by mechanical energy transfers at variety of temporal scales
-coasts are rapid-response systems that adapt to new equilibriums (overall younger systems)
-they are under threat from rising sea levels
coastal system
- Coasts occur where the world’s oceans and seas meet the margins of
the land masses. - Estimates that 65% of world’s population lives within a few kilometers
of the coast.
Coastal sources of energy
tides and waves
Tides
originate from the gravitational pull of the moon and sun in
combination with the rotational energy of the earth
- Regular oscillations in tide level are created subject to biweekly variation can range from
0.5-10 m - Variation in atmospheric pressure can depress or raise sea level (low pressure Hurricanes
sea surges) - define the range of elevation in which direct wave and other marine action takes place
- flow and ebb of tides around coastal irregularities create tidal currents
- diurnal alternations of inundation and exposure of the intertidal zone create conditions for
particular rock weathering processes - create the intertidal habitat to which a range of plant and animal organisms is adapted and which
may have geomorphological effects - With each tide an influx of nutrients is supplied to intertidal organisms
Waves
are created by the wind shear across the ocean (ultimately powered
by solar energy)
What is the most important agent of coastal change?
wave action
What determines wave height?
Wind speed, duration
of wind, and Fetch
determine
Where do waves travel faster?
in open water
Where do waves travel slower?
in shallow water
What do currents do?
Currents (wave induced, tidal, wind-induced) transport sediments and
may entrain sediments
salt weathering
a form of mechanical weathering or physical weathering of rock that occurs when salt spray from the sea gets into a crack in a rock, evaporates and crystallizes putting pressure on the surrounding rock and weakening its structure; most common in arid climates
