Macquarie Island

Some of this island's rocks were once deep under the ocean floor.

The Earth's moving plates pushed them up.

Macquarie Island is the top of an undersea ridge, the Macquarie Ridge, pushed up where two of the Earth's plates meet: the Indo-Australian Plate and the Pacific Plate.

UNESCO says it is the only place on Earth where rocks from the mantle, normally 6 kilometers below the ocean floor, are being actively pushed above sea level. The island also has pillow basalts, lava rocks shaped like pillows.

According to UNESCO, the island is the exposed crest of the undersea Macquarie Ridge, raised to its present position where the Indo-Australian tectonic plate meets the Pacific plate. It is a site of major geoconservation significance: the only place on Earth where rocks from the mantle (6 km below the ocean floor) are being actively exposed above sea level.

These exposures include excellent examples of pillow basalts and other extrusive rocks, which UNESCO lists among the island's unique features.

Millions of penguins and seabirds come to the island.

Elephant seals come to its beaches too.

Tasmania's park service says about 3.5 million seabirds and 80,000 elephant seals come to Macquarie Island each year to breed and molt. The Australian Antarctic Division says up to 4 million penguins are regular visitors.

The island lies close to the Antarctic Convergence, where nutrient-rich Southern Ocean water meets warmer water, making rich feeding grounds for penguins, seals and seabirds.

Tasmania Parks and Wildlife Service: around 3.5 million seabirds and 80,000 elephant seals arrive each year to breed and molt. The Australian Antarctic Division (AAD) counts up to 100,000 seals and 4 million penguins as regular visitors, and links the rich feeding grounds to the nearby Antarctic Convergence.

The AAD says rabbits, rats and mice, brought over nearly 200 years, were removed by 2014 after a 7-year project, and the island is returning to lush green. It also reports dieback in the endemic cushion plant Azorella macquariensis, which scientists in 2015 linked to drier, windier conditions caused by climate change.

People work hard to keep the island's animals and plants safe.

Some beaches are closed at times so animals are not disturbed.

Macquarie Island is a Tasmanian nature reserve and a World Heritage site. Parts of the coast are closed at some times of the year to protect threatened wildlife.

To its south and east, the Macquarie Island Marine Park protects the ocean home of royal and southern rockhopper penguins, fur seals, elephant seals and five kinds of albatross.

The AAD notes the island and its waters to 3 nautical miles are a gazetted Tasmanian Nature Reserve, and access to many coastal areas is restricted at times to protect threatened wildlife, critical habitat, special ecosystems or historic places, with rangers advising expeditioners.

The Commonwealth Macquarie Island Marine Park, declared in 1999 (162,000 km² then, 475,465 km² now), protects habitat of threatened species such as the royal and southern rockhopper penguins, the subantarctic fur seal, the southern elephant seal and five albatross species.

Penguins and seals often rest near people's buildings.

Visitors must keep away so they do not disturb them.

The Australian Antarctic Division says seals and penguins often rest beside the station's buildings, so people must take care not to disturb them. Tasmania's park service says the island is far enough south that few people can go there, and it takes the full force of the Southern Ocean.

The AAD asks that care be taken to minimize disturbance, since seals and penguins commonly rest in the shelter of station buildings, and rangers advise on restricted special management areas.

Tasmania Parks and Wildlife Service notes the island is far enough south that human access is limited, and that it is subject to the full force of the Southern Ocean.