The Macquarie Island is recognized as island rich of wide varities of animal and plants. It provides evidence of the rock types found at great depths in the earth's crust and of plate tectonics and continental drift, the geological processes that have dominated the earth's surface for many millions of years.
It is the only island in the world composed entirely of oceanic crust and rocks from the mantle - deep below the earth's surface.
Macquarie Island probably began as a spreading ridge under the sea with the formation of new oceanic crust somewhere between 11 and 30 million years ago.
At some stage the spreading halted and the crust began to compress, squeezing rocks from deep within the mantle upward like toothpaste from a tube. As the ridge grew it eventually became exposed above the ocean's surface about 600,000 years ago. Thus, rocks normally only occurring deep within the earth's mantle have become exposed on the earth's surface.
Since Macquarie Island emerged, it has mainly been carved by marine processes such as wave action, unlike other subantarctic islands, which have been shaped by glaciers.
The geodiversity of Macquarie Island provides the foundation for the landforms, soils, plants and animals occurring here. It is an island of unique natural diversity, a site of major geoconservation significance and one of the truly remarkable places on earth.
Around the shoreline there is a coastal terrace formed from a wave-cut platform now raised above sea level. Vast waterlogged areas on the coastal platform are heavily vegetated, forming a mire based on deep peat beds and known locally as "featherbed" from the sensation gained when walking over them. Old sea stacks testify to the continual uplifting of the island as they protrude through the peat beds, some of them now being several hundred metres from the existing coastline.
Behind the coastal terrace, steep escarpments rise more than 200 metres to the undulating central plateau which has three peaks over 400 metres, the highest being Mt Hamilton at 433 metres. The plateau scarps are most spectacular at the southern end of the island and along the west coast where the relentless pounding by the Southern Ocean has cut a myriad of rugged bays and coves, fringed with sea stacks and reefs.
The plateau surface is dotted with innumerable lakes, tarns and pools, mainly of structural origin. Fluctuations in sea level and marine erosion have cut away the original escarpments leaving some lakes now perched on the edge of the plateau, while others have been partially or totally drained. The continual westerly winds, which increase in force as they rise over the barrier of the island, and changes in the topography on the plateau, result in dramatic changes in the vegetation cover.
Among the most aesthetically appealing sights of the island are the vast congregations of wildlife, particularly penguins, on suitable parts of the coastal terrace, especially during breeding seasons. The breeding population of royal penguins on Macquarie Island is estimated at over 850,000 pairs - one of the greatest concentrations of sea birds in the world.
Four species of albatross nest on steep and rugged cliffs, both on the main island and on nearby Bishop and Clerk Islands. These are majestic birds, easily viewed when nesting.
Elephant seals also form impressive colonies during the breeding season on suitable beaches. These animals can grow to over 4.5 metres in length and to a weight of 3.5 tonnes. Conflicts between the larger bulls are among the more memorable sights that may be witnessed on the island.
The terrestrial area of Macquarie Island is a State Reserve with protection extending to low water mark. The marine values are protected by the Macquarie Island Marine Park declared by the Commonwealth on 28 October 1999. The primary purpose of the marine park is to protect the conservation values of the region from human disturbance. The marine park contains the world's largest marine highly protected zone, covering more than 16 million hectares.
There are no permanent human inhabitants on Macquarie Island although the Australian Antarctic Division station is occupied year round. The only access to the island is by sea and there are no harbours or landing facilities. Ship-traffic in the area is minimal and mainly consists of resupply vessels for the station. |
