Coral Reefs - Geomorphic processes
Continental drift
The movement of the earth's plates and the associated rifting, have enabled coral to grow as oceanic plates have moved into tropical areas.
Subsidence
The rate of subsidence and sea level has determine reef growth over time. If the lithosphere subsides too far the water will be too deep for coral growth. If land subsides into the water it can create the right conditions for coral growth.
Most coral reefs consist of thick sequences of accumulated skeletal fragments of calcium carbonate (limestone). Life on the reef is confined to the surface of the massive limestone rocks. When corals and other organisms die their hard parts are added to the reef edifice. This results in upward and lateral growth of the coral reef over long periods of time.
Weathering and erosion
The calcium carbonate (or limestone) that the reef is made of is subject to chemical weathering. The limestone is broken down by carbonic acid formed partly from rain (freshwater) and carbon dioxide.
Waves and winds cause mechanical weathering of the corals. This is where parts of the corals are broken off, and then these broken pieces rub and crash against live coral causing more coral to break off.
Bioeroders, e.g. grazing fish, boring sponges and bivalaves, and algae contribute to the physical breakdown of the reef by biting bits of coral off or boring into the coral colonies, weakening them and eventually causing them to collapse or dissolve.
The movement of the earth's plates and the associated rifting, have enabled coral to grow as oceanic plates have moved into tropical areas.
Subsidence
The rate of subsidence and sea level has determine reef growth over time. If the lithosphere subsides too far the water will be too deep for coral growth. If land subsides into the water it can create the right conditions for coral growth.
Most coral reefs consist of thick sequences of accumulated skeletal fragments of calcium carbonate (limestone). Life on the reef is confined to the surface of the massive limestone rocks. When corals and other organisms die their hard parts are added to the reef edifice. This results in upward and lateral growth of the coral reef over long periods of time.
Weathering and erosion
The calcium carbonate (or limestone) that the reef is made of is subject to chemical weathering. The limestone is broken down by carbonic acid formed partly from rain (freshwater) and carbon dioxide.
Waves and winds cause mechanical weathering of the corals. This is where parts of the corals are broken off, and then these broken pieces rub and crash against live coral causing more coral to break off.
Bioeroders, e.g. grazing fish, boring sponges and bivalaves, and algae contribute to the physical breakdown of the reef by biting bits of coral off or boring into the coral colonies, weakening them and eventually causing them to collapse or dissolve.
Hydrological processes
Wave action
The movement of water to form waves creates tiny bubbles of oxygen which are essential for the growth of corals.
Waves can break corals. During times of cyclones and storms waves can turn large areas of coral reefs into piles of rubble. It can take anywhere from 10-25 years for the reef to recover, depending on what state the reef was in.
Currents
Currents are responsible for much of the transport and deposition of sediment, plant life and seeds and marine migration of organisms.
The movement of water to form waves creates tiny bubbles of oxygen which are essential for the growth of corals.
Waves can break corals. During times of cyclones and storms waves can turn large areas of coral reefs into piles of rubble. It can take anywhere from 10-25 years for the reef to recover, depending on what state the reef was in.
Currents
Currents are responsible for much of the transport and deposition of sediment, plant life and seeds and marine migration of organisms.
