Section 4: Rocks from Reefs

 Structure of calcite (calcium carbonate - CaCO 3 ) skeletons built up by coral animals in warm, shallow ocean water

 Most are smaller than your fingernail  Tiny algae grow within body and provide substances that the coral needs to live; coral provides structure to algae

 What type of relationship do the coral animal and algae have?

 A symbiotic relationship

 Coral animal skeletons made when they absorb Ca from water and combine it with C and O to form calcite  When animals die, skeletons remain  More corals build on top of them, gradually forming a reef

 How do coral reefs form?

 The calcite skeletons of coral animals remain after the animals die and then more build up on top of them.

 Within 40 meters of water’s surface because algae needs sunlight  Warm water of tropical oceans  US: Florida & Hawaii  Australia – Great Barrier Reef

 If sea level rises above a coral reef, what may happen to the reef?

 If sea level rises slowly, the reef might build upward. If sea level rises too quickly, the reef could die.

 Coral reef = organic limestone  Limestone deposits that began as reefs provide evidence of how plate motions have changed Earth’s surface and of past environments  Ex. Wherever there were reefs, there were once a warm climate and shallow ocean water (Midwest & Southwest US)

 A geologist finds an area abundant in limestone. What can the geologist infer about that area?

 S/he can infer that at the time when the limestone formed, the area was in a warm climate and was covered by shallow ocean water.

1. Which element does not make up a coral reef? a. calcium b. carbon c. boron d. oxygen

2. How do coral reefs form? a. coral plants die and their stems form the reef b. coral animals die and their skeletons form the reef c. algae hardens and crystallizes d. rock sediment compacts and cements together

3. Which of the following is not something that corals need to live? a. deep water b. sunlight c. algae d. warm water

4. What type of rock does coral reef form? a. clastic limestone b. clastic sandstone c. organic sandstone d. organic limestone

5. Remains of a coral reef provide evidence of which of the following? a. the climate in that area was warm and covered in water b. the climate in that area was cold and dry c. the climate in that area was cold and wet d. the climate in that area was warm and dry