Coasts and Reefs: Shallow Marine Processes (L19) Flashcards
what is the Zen factor of why people go to the beach?
To feel like one belongs to something bigger
what are the 2 sociological factors on why people go to the beach?
the beach provides opportunities to strip way inhibitions that are present in urban environments
the beach environment is also a place to watch people act out their vanity and reveals the primal behaviour of adult humans
What is the “fair-weather wave base”?
The maximum water depth affected by normal, day-to-day wave activity
what are the circles found in the diagram?
these are the orbital paths water takes when affected by waves
(circles decrease in diameter with depth, due to the smaller amount of water movement at greater depths below the surface)
What are the Main “zones” (from sea toward the land)?
the offshore to shoreface to foreshore and to the backshore
what is the offshore zone?
the zone that is below the fairweather wave base and unaffected by normal waves
why is the mud deposited in the offshore zone? What is an exception?
b/c regular waves don’t disturb the seafloor leading to the lack of agitation
during storms, wave base extends downward to a greater depth, and sand may be deposited above storm wave base
what is the shoreface?
the zone above the “fair-weather wave base” but below the low tide level
what are the characteristics of the shoreface?
gentle, concave-upward shape
sediment is mostly sand (mud is swept away by fairweather waves)
how are sandbars developed in the upper shoreface?
when a wave breaks, there is a loss of energy and sand is locally deposited from suspension
what is the foreshore?
where water and land meet. The lower, “wet” part of “beach” and is affected by swash and backwash
lies just below the water surface at high tide, but exposed to air during the low tide
what is another name for the foreshore and why?
known as the interidal zone - as foreshore is between the levels of low and high tide
how are much of the sediment returned back to the upper shoreface?
through backwash
what is the backshore?
the upper, dry part of the “Beach” and lies above high-tide level
how is the sediment in the backshore deposited and trasported?
by wind b/c sand is mobile due to lack of anchoring plants
what are the 2 ways shorelines differ?
some are dominated by deposition, others are dominated by erosion
what type of shoreline is an important supplier of beach sediment?
shorelines characterized by exposed bedrock and strong wave activity
Mature sand that has undergone lots of weathering tend to be domainted by ____
minerals such as quartz
what are most of the grains of white sand on Hawaiian beaches made out of?
little pieces of shell, coral, and other grains of carbonate sediment derived from marine organisms
what happens when a river enters a large body of water? what is this called?
its flow rapidly decreases, resulting in the deposition of sediment at the river mouth
called a Delta
How did the birdsfoot delta get its shape?
b/c wave activity isn’t strong enough to redistrubute the sediment very much
Why are sediment particles transported in a zig-zag pattern along the beach?
b/c the direction of swash is oblique but the backwash runs back at a right angle due to gravity
what is a longshore current?
a current that flows parallel to the shore
what do you call the movement of shoreface sediment by a longshore current?
longshore drift
what would happen if we didn’t have beach drift and longshore currents
there would be no redistributing sediment from river mouths, and many beaches would be sandless
what are rip currents?
breakin waves apporaching the beach carry water but it has to escape back to the sea somehow so uses various “paths of least resistance” to funnel back into the sea
What is an undertow?
like an exceptionally strong backwash that continues underwater into the shoreface zone when water can’t escape as a rip current
what are reefs?
natural structures of rock formed by marine animals in shallow marine settings
reef-building organisms build skeletons of calcium carbonate in the form of ____
aragonite or calcite
why are coral reefs often called the “rainforests of the sea”
due to the great diversity of creatures that form them
how do coral reefs get their brilliant colors?
from the microscopic algae in the coral tissues
what conditions are necessary for reef development?
warm seawater areas of the tropics
calcium carbonate as it is easier to percipate in warm water than in coldwater
what are the 3 areas where reefs tend to form?
areas where little clastic sediment occurs
where nutrient levels are low (as if too high, seweed takeover)
where water is shallow
what is an atoll?
a special kind of reef that is ringshaped with a central lagoon
how is an atoll formed?
first as a reef that fringes a volcanic island
As the island sinks, the reef continues to build upward, eventually ending up as a ring-shaped structure
What is Bikini Atoll?
a site famous for beingthe first nuclear test post ww2, and remains super radioactive to this day
