How chalk cliffs are formed?
They’re formed from the skeletal remains of minute planktonic green algae that lived floating in the upper levels of the ocean. When the algae died, their remains sank to the bottom of the ocean and combined with the remains of other creatures to form the chalk that shapes the cliffs today.
What causes limestone?
Limestone is formed in two ways. It can be formed with the help of living organisms and by evaporation. Ocean-dwelling organisms such as oysters, clams, mussels and coral use calcium carbonate (CaCO3) found in seawater to create their shells and bones. The water pressure compacts the sediment, creating limestone.
When was limestone formed?
Limestone may have been deposited by microorganisms in the Precambrian, prior to 540 million years ago, but inorganic processes were probably more important and likely took place in an ocean more highly oversaturated in calcium carbonate than the modern ocean.
How are coral reefs formed and how are they formed?
Coral reefs begin to form when free-swimming coral larvae attach to submerged rocks or other hard surfaces along the edges of islands or continents. As the corals grow and expand, reefs take on one of three major characteristic structures — fringing, barrier or atoll.
What are the characteristics of a coral reef?
As the corals grow and expand, reefs take on one of three major characteristic structures —fringing, barrier or atoll. Fringing reefs, which are the most common, project seaward directly from the shore, forming borders along the shoreline and surrounding islands.
What are the major divisions of a coral reef?
The major divisions common to most reefs, as they move seaward from the shore, are the reef flat, reef crest or algal ridge, buttress zone, and seaward slope. Corals usually develop into one of three characteristic structures: fringing reefs, barrier reefs or atolls. Learn more and view a larger image.
How is calcium carbonate produced in the ocean?
Although carbonate is produced in the open ocean(pelagic, see Chapter 5), this chapter concentrates on production in coastal waters (neritic) because this contributes sediment to the coast through skeletal breakdown producing sand and gravel deposits on beaches, across continental shelves, and within reefs.