Coasts and Reefs: Shallow Marine Processes (L19)

Question 1

what is the Zen factor of why people go to the beach?

Answer 1

To feel like one belongs to something bigger

Question 2

what are the 2 sociological factors on why people go to the beach?

Answer 2

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

Question 3

What is the “fair-weather wave base”?

Answer 3

The maximum water depth affected by normal, day-to-day wave activity

Question 4

what are the circles found in the diagram?

Answer 4

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)

Question 5

What are the Main “zones” (from sea toward the land)?

Answer 5

the offshore to shoreface to foreshore and to the backshore

Question 6

what is the offshore zone?

Answer 6

the zone that is below the fairweather wave base and unaffected by normal waves

Question 7

why is the mud deposited in the offshore zone? What is an exception?

Answer 7

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

Question 8

what is the shoreface?

Answer 8

the zone above the “fair-weather wave base” but below the low tide level

Question 9

what are the characteristics of the shoreface?

Answer 9

gentle, concave-upward shape

sediment is mostly sand (mud is swept away by fairweather waves)

Question 10

how are sandbars developed in the upper shoreface?

Answer 10

when a wave breaks, there is a loss of energy and sand is locally deposited from suspension

Question 11

what is the foreshore?

Answer 11

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

Question 12

what is another name for the foreshore and why?

Answer 12

known as the interidal zone - as foreshore is between the levels of low and high tide

Question 13

how are much of the sediment returned back to the upper shoreface?

Answer 13

through backwash

Question 14

what is the backshore?

Answer 14

the upper, dry part of the “Beach” and lies above high-tide level

Question 15

how is the sediment in the backshore deposited and trasported?

Answer 15

by wind b/c sand is mobile due to lack of anchoring plants

Question 16

what are the 2 ways shorelines differ?

Answer 16

some are dominated by deposition, others are dominated by erosion

Question 17

what type of shoreline is an important supplier of beach sediment?

Answer 17

shorelines characterized by exposed bedrock and strong wave activity

Question 18

Mature sand that has undergone lots of weathering tend to be domainted by ____

Answer 18

minerals such as quartz

Question 19

what are most of the grains of white sand on Hawaiian beaches made out of?

Answer 19

little pieces of shell, coral, and other grains of carbonate sediment derived from marine organisms

Question 20

what happens when a river enters a large body of water? what is this called?

Answer 20

its flow rapidly decreases, resulting in the deposition of sediment at the river mouth

called a Delta

Question 21

How did the birdsfoot delta get its shape?

Answer 21

b/c wave activity isn’t strong enough to redistrubute the sediment very much

Question 22

Why are sediment particles transported in a zig-zag pattern along the beach?

Answer 22

b/c the direction of swash is oblique but the backwash runs back at a right angle due to gravity

Question 23

what is a longshore current?

Answer 23

a current that flows parallel to the shore

Question 24

what do you call the movement of shoreface sediment by a longshore current?

Answer 24

longshore drift

Question 25

what would happen if we didn’t have beach drift and longshore currents

Answer 25

there would be no redistributing sediment from river mouths, and many beaches would be sandless

Question 26

what are rip currents?

Answer 26

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

Question 27

What is an undertow?

Answer 27

like an exceptionally strong backwash that continues underwater into the shoreface zone when water can’t escape as a rip current

Question 28

what are reefs?

Answer 28

natural structures of rock formed by marine animals in shallow marine settings

Question 29

reef-building organisms build skeletons of calcium carbonate in the form of ____

Answer 29

aragonite or calcite

Question 30

why are coral reefs often called the “rainforests of the sea”

Answer 30

due to the great diversity of creatures that form them

Question 31

how do coral reefs get their brilliant colors?

Answer 31

from the microscopic algae in the coral tissues

Question 32

what conditions are necessary for reef development?

Answer 32

warm seawater areas of the tropics

calcium carbonate as it is easier to percipate in warm water than in coldwater

Question 33

what are the 3 areas where reefs tend to form?

Answer 33

areas where little clastic sediment occurs

where nutrient levels are low (as if too high, seweed takeover)

where water is shallow

Question 34

what is an atoll?

Answer 34

a special kind of reef that is ringshaped with a central lagoon

Question 35

how is an atoll formed?

Answer 35

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

Question 36

What is Bikini Atoll?

Answer 36

a site famous for beingthe first nuclear test post ww2, and remains super radioactive to this day