Lecture 12 flashcards
(30 cards)
Three things that vary place to place:
T, G-M, C
topography, geologic makeup, climate
what two processes converge along coasts to create landscapes that frequently undergo rapid change?
Continental and oceanic
Shorelines are ____ zones between what two environments?
Transitional zones between continental and maritime environments.
the wave height, length and period all depend on (3)
- the wind speed
- the length of time the wind has blown
- the fetch (distance that the wind has travelled across open water)
As the quantity of energy transferred from ind to water increases, what two other things increase as well?
height and steepness of the waves
what are the seas aves that we watch from shore a mixture of? (2)
- swells from faraway storms
- waves created by local winds
T/F: in open waters, it is the wave energy that moves forward, not the water itself
True
Describe the wave base
beneath the surface - the circulation motion rapidly diminishes until (at a depth of about 1/2 the wavelength, the movement of water particles becomes negligible)
T/F: as long as a wave is in deep water, it is unaffected by water depth
true
T/F: the wave begins to “feel bottom” at a water depth equal to about 1/2 its wavelength (wave base)
true
What process involves the bending in direction of waves as they enter shallow water, with a net result of a wave that may approach nearly parallel to the shore regardless of the original direction?
Wave refraction
wave impact is concentrated against the sides and ends of headlands and project into water, but wave attack is weakened in bays - what is this a result of?
wave refraction
Describe beach drift:
the zigzag pattern of water and sediment transport along the beach - most waves reaching the shore at an angle, and returning backwash is straight
what are tides controlled by?
the gravitational attraction between Earth and the Moon (with a smaller influence from the sun)
describe tidal currents (flood currents and ebb currents, herringbone cross-bedding)
Tidal current: the term used to describe the horizontal flow of water accompanying the rise and fall of the tide
Flood currents: when it comes in/
Ebb currents - tide falls
Cross-bedding in sedimentary layers as a record of the back-and-forth migration of underwater bedrooms in response to reversing current direction int he flood-ebb cycle
Describe the 3 steps involved in making a sea stack
- erosion
- sea caves
- sea arch
- sea stack
What is the offshore zone?
s permanently submerged underwater and lies below the average depth at which waves touch the sea bottom during normal fair-weather conditions
what is the shore face zone?
lies landward of the offshore zone
Characterized by constant day-to-day sediment transport in shallow water, between the fair-weather wave base and the low-tide mark
what is a beach?
area of unconsolidated sediment that can be loosely considered to extend from the shoreface to the seaward limit of permanently vegetated land
what is a spit?
an elongated ridge of sand that projects from the land into the mouth of an adjacent bay. The end in the water commonly hooks landward in response to the dominant direction of the longshore current
what is a baymouth bar?
sandbar that completely crosses a bay – seals it from the open ocean. Tends to form across bays where currents are weak, allowing a spit to extend to the other side
what is a tombolo?
produces a ridge of sand that connects an island to the mainland or to another island
what is this a description of?
“a low, elongate ridge of sand that parallels the coast”
barrier islands
describe hard stabilization
structures that are built to protect a coast from erosion or to prevent movement of sand along a beach
