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How Was The Great Barrier Reef Formed?

Maya Pillai Jan 11, 2021
The Great Barrier Reef is not only the largest living structure, but is also the largest coral reef in the world. It was formed due to successive rise and fall of sea levels during the final years of the last Ice Age.
The Great Barrier reef is one of the seven natural wonders of the world, and was declared as a World Heritage Site in 1981. A popular Australian tourist destination, it attracts thousands of vacationers from all over the world.
The Great Barrier Reef
It acts as a natural barrier for the eastern coast of Australia by limiting the wave force, which is generated from the strong water surges that hit the coastline. There are coral reefs that are older than the Great Barrier Reef along the coast of southern Europe.
The Great Barrier Reef lies along the northeast coast of Queensland, in the Coral Sea of Australia. It measures about 1600 miles along its length, up to 40 miles in width, and is 130000 sq. miles in terms of area.
 In the geographical context, this structure extends from the Torres Strait in the north, to the Fraser Islands in the south. It is made up of almost 3000 individual reefs, and is separated from the coast by about 15 to 80 miles of water.
The Great Barrier reef requires adequate amounts of sunlight, and the corals grow only in shallow and clean water. The reef can be made out of sand, rock, or coral.
The temperature that is conducive for coral formation is between 18 to 30° C. The current structure of the reef is around 8000 years old. Sea animals called polyps form the reef colonies. A coral polyp resembles a sea anemone, and it has many tentacles around its mouth. Many polyps join together to form a colony.
The Barrier Reef is made of extensive individual coral reefs.
Each polyp is associated with a type of algae; the latter carries out the process of photosynthesis that helps the polyp to form a coral skeleton, which is usually made up of aragonite, a mineral that consists of calcium carbonate. These skeletons form quickly, and are established as the foundation on which the reefs are built.
Two skeletons are sealed together by calcium carbonate that is produced by algae. Approximately 400 species of corals are found in this area, and it supports around 2000 varieties of fish. Currently, around 4000 species of mollusk have been identified, which grow in this region.
According to several years of research, this reef range started forming about 18-25 millions years ago. Since then, the growth has intermittently halted and resumed due to the changing climatic conditions and the rise and fall of the sea levels.
The Great Barrier Reef is believed to have formed on this pre-existing base, during the Last Glacial Maximum (LCM) or the last Ice Age period, around 26,000 years ago. Its history is quite complex.
The plate tectonic theory (motion of the lithosphere), indicates that the continent of Australia has moved approximately 7 cm per year, since the Cenozoic era. This movement caused this landmass to experience an uplift that raised it above the normal sea level.
This was accompanied by regular volcanic eruptions. The present reef is the cumulative result of coral growth for the past 6000-8000 years, on the platform of an older reef.
The combined effect of both these events was evidenced in the formation of high islands around the landmass. The stabilization of volcanic activity led to the formation of a sea and a sea basin. It was in this basin, that the coral reefs first started growing.
 Due to subsequent sea level and climate changes, the growth of the reek was severely affected, around 600,00 years ago.
This event was soon followed by the last glacial maximum, or the last ice age, which ended approximately 26,000 years ago. this led to the rise in sea level. As the sea level rose and submerged the volcanic islands, corals began to grow on these hills and flourish around the coasts off Australia.
As the sea levels further increased, so did the coral reef populations, in order to form the great barrier reefs that can be evidenced and observed today.

Global Warming and the Great Barrier Reef

Global warming is a threat to the coral reefs, and they are also endangered by unprecedented climatic change. When the ocean temperature increases, coral bleaching occurs, and the symbiotic alga inside the polyps die.
Eventually, the polyps also start to lose their color, turn white, and die. In 1998, coral bleaching affected approximately 90% of the Great Barrier Reef.
The coral ecosystem is bound to get physically damaged, if there is an increase in the sea levels, and also in the frequency of tropical storms. Curbing global warming can prevent the destruction of this reef, which is home to numerous species of plants and animals.
Currently, efforts are being taken by the Australian government to reduce the beaching effect in this region. Also, many concerned organizations are trying to reduce the greenhouse gas emissions for protecting this reef.
Awareness needs to be generated among people, mainly about the reasons why global warming is responsible for the bleaching effect, and how the pollution of oceanic regions is affecting the reef flora and fauna.
Though reefs are known to flourish in warm waters, it does not mean that global warming will be helpful for their thriving. In this case, the temperature of water increases well beyond the 18 to 30° C, and hence, global warming proves to be a bane for this natural wonder.
The formation of oceanic structures like coral reefs takes a very long time, and requires a specific set of conditions. If destroyed, they might take thousands of years to regrow.
Looking at the current rate of destruction, it has been estimated that almost 70% of the coral species will be destroyed till the year 2050. Taking concrete steps towards saving the Great Barrier Reef is of utmost importance.