Carl Reefs 2 Flashcards

1
Q

What are the critical necessities of coral reefs?

A
  • access to light
  • areas of moderate currents
  • maintain the positions over long time
  • clear water
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2
Q

Around which two things do we expect to see corals?

A
  • shallow waters (between 25-60m), often near land

- initially, access to substrate that is fixed in position.

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3
Q

in what two broad types can corals be divided?

A
  • atolls

- coastal reefs

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4
Q

define atoll

A

coral reefs found most often in open ocean with no associated geological land masses

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5
Q

define coastal reefs, and what are their sub-divisions

A
  • associated with continental or volcanic land masses.

- fringing, barrier reefs

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6
Q

how deep can atolls go?

A

thousands of meters or more

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7
Q

where are the majority of atolls found?

A

indo-pacific

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8
Q

what was the name of the battle and atoll that was pivotal in the second wold war?

A

The battle of Midway. june 1942

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9
Q

what are some physical characteristics shared by atolls?

A
  • ring shaped
  • sandy lagoons within the reef
  • reefs are often open on the windward end, resembling a horseshoe
  • often very flat and low elevation
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10
Q

what is the name of Darwin’s ship, what year did he discover atolls

A

HMS Beagle, 1830s

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11
Q

explain the timeline it takes for a coral atoll to form

A
  • fringing reef takes 10,000 years
  • over 100,000 years reef will expand
  • as the interior island subsides beneath the water, it can take up to 30,000,000 years for the atoll to form.
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12
Q

what discoveries proved darwin’s theory of the origin of atolls?

A
  • scientists drilled >1400 ft into an atoll before they found volcanic rock
  • remnants of dead surface reefs on seamounts show where volcanoes sank too quickly for reefs to maintain contact with light
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13
Q

describe fringing reefs and their associated ecology

A
  • found in a band close to the fringe of the shoreline
  • consist of an inner reef flat and a reef slope
  • inner flat is mostly sandy, muddy, and has coral rubble
  • the shoreline can be home to mangroves
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14
Q

how are fringing reefs affected from terrestrial elements?

A
  • freshwater runoffs
  • terrestrial erosion
  • more extreme temperature variations
  • prolonged exposure during low-tides
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15
Q

how are fringing reefs and barrier reefs different?

A
  • barrier are much further offshore
  • their lagoons are much larger and deeper
  • extensive reefs on the inner shore of barrier as well as outer
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16
Q

what accounts for the great diversity and zonation of corals foud in coral reefs?

A
  • difference in environmental conditions:
  • salinity
  • turbidity
  • depth
  • gradient
17
Q

what are patch reefs?

A

small, isolated reefs that grow up from the open bottom of the island platform or continental shelf.

  • usually occur between fringing reefs and barrier reefs
  • rarely reach the surface water
18
Q

what contribute to the growth of coral reefs?

A
  • ground subsidence

- ocean level changes

19
Q

what is the highest point of the reef called?

-what are some of its features?

A
  • reef crest or breaker zone
  • dominated by corals and is often the richest coral area of them all
  • can be largely covered by coralline algae depending on reef height and depth and strength of wave action