Coastal Systems & Wind Processes Flashcards
How do coastal environments place in the geologic time scale?
relatively young
What interactions form coastal environments (5)?
- land
- ocean
- atmosphere
- sun
- moon
What are the three zones of a coastal environment?
- littoral zone: extends into the water until wave action does not affect sediment on the seafloor
- shoreline: where the sea and land meet
- coast: extends until the first major landform change
What is the mean sea level and how does it vary (4)?
- based on average tidal levels recorded hourly over many years
- varies around the world based on ocean currents, tides, temp. of air and ocean, air pressure, prevailing winds, gravity, and oceanic volume
- sea levels change through climate change, tectonic activity, and glaciation
- over the past 100 years, sea level has been increasing
What are tides (3)?
- twice-daily osceillations in sea level
- locations around the world experience different tidal fluctuation
- exist in oceans and very large lakes
What causes tides (4)?
- tidal bulge: water on Earth is pulled outward by the Sun and Moon
- shift from high tide to low tide caused by Earth’s rotation through the tidal bulge
- spring tide: higher tides occur when Earth and Moon align with the Sun and pull in the same direction
- neap tide: lower tides occur when Earth and Moon are not aligned with the Sun, weakening gravitational force
What is tidal range?
the difference between consecutive high and low tides
What are waves and how do they vary in scale (2)?
- form as a result of friction between wind and ocean surface
- can be large and powerful or small and weak
What are swells (3)?
- regular patterns of smooth, rounded waves that exist in the open ocean
- swells compress and become top-heavy as they move closer to the coast
- breaker waves form when the swell becomes too top-heavy and collapses over itself
What are tsunamis (4)?
- form in the aftermath of an earthquake, landslide, or volcanic eruption below the ocean’s surface
- movement displaces a huge amount of water, creating large waves
- travel at a very fast rate
- have a large wavelength but a low height
What are erosional coastlines (5)?
- more erosion occurring
- aka “emergent coastlines”
- found along Pacific coast of U.S.
- more common in areas with tectonic activity
- waves act to erode away material and straighten coastline
What are seven features of erosional coastlines?
- headlands: protruding landforms of erosion-resistant rock
- refracted wave fronts: waves hit furthest point of headland and bend to attack the sides of that point, resulting in…
- sea caves
- sea arches
- sea stacks
- sea cliffs
- wave-cut platforms
What are depositional coastlines (3)?
- more deposition occurring
- aka “submergent coastlines”
- found along Gulf Coast and Atlantic Coast of U.S.
What are three features of depositional coastlines?
- barrier spit: sandbar which extends parallel along shoreline in same direction as longshore drift; does not extend entirely along bay
- lagoon: small body of water formed when the bay has been completely cut off by the barrier spit
- tombolo: barrier spit which extends perpendicular to shoreline, connecting an off-shore island
What determines the material which makes up beaches?
the type of rock which makes up the coastline
What are barrier islands (5)?
- long, narrow island which runs parallel to shoreline
- absorb energy associated with wave activity
- most common along depositional coastlines
- popular for beach resorts (a bad idea)
- creates swampy backbay area
What is eolian erosion (4)?
- wind erosion
- less landforms associated
- more common in arid environments
- deflation vs abrasion
What is deflation (2)?
- removal and lifting of individual, loose particles
- forms desert pavement: larger particles cemented in place
What are two explanations for desert pavement?
- deflation hypothesis: wind removes fine particles, leaving larger materials to consolidate into pavement
- sediment accumulation hypothesis: wind delivers fine particles that settle and wash downward as larger gravels migrate upward during cycles of swelling and shrinking, resulting in pavement
What is abrasion (3)?
- grinding of rock surfaces by tiny particles
- yardang: elongated ridges created via abrasion
- ventifact: irregular rock shape formed by irregular wind patterns (can also form via glacial erosion)
What are the three types of eolian transportation?
- suspension
- saltation
- surface creep
What is suspension?
transportation of fine, wind-blown particles
What is saltation (2)?
- transportation of particles heavy enough to be moved via skipping motion along the surface
- the most common form of eolian transportation
What is surface creep?
transportation of larger particles which creep/roll along the surface
What are the two formations associated with eolian deposition?
- loess
- sand dune
What is a loess (3)?
- very fine, wind-blown glacial silt
- common in Alaska, Great Plains, and Mississippi River Valley in U.S.
- create fertile soil
What is a sand dune (3)?
- only a small portion of deserts consist of sand dunes
- constantly moving hill of sand
- migrate based on prevailing wind direction
What are the three characteristics of a sand dune?
- windward slope (gradual)
- leeward slope (steep)
- slipface: leeward slope of sand dune; constantly moving downward
What are the five classes of sand dunes?
- crescentic: curved shape with horns pointed downwind; found in areas with constant winds and little directional variability where limited sand is available
- linear: straight, slightly sinuous, ridge-shaped dune aligned parallel with the wind direction
- star: pyramidal-shaped structure with three or more sinuous, radiating arms extending outward from a central peak; results from effective winds shifting in all directions
- parabolic: crescent-shaped dune with opening end facing upwind; U-shaped “blowout” and arms anchored by vegetation, which stabilizes dune form
- dome: circular or elliptical dune with no slipface; sometimes modified into barchanoid forms, and sometimes stabilized by vegetation
