Friday, February 1, 2013

Ball's Pyramid

Ball’s Pyramid is not a man-made pyramid, but the remains of a basaltic shield volcano that emerged from the sea less than 7 million years ago. It is 562 metres high and 1,100 metres in length, making it the tallest volcanic stack in the world. It juts out of the Pacific Ocean, off the coast of Australia, 20 kilometres southeast of Lord Howe Island. Ball’s Pyramid is named after the British naval officer, Lieutenant Henry Lidgbird Ball, who was the first European to see it in 1788.

The island is comprised almost entirely of nearly horizontally-bedded lava flows which are the remains of a volcanic plug from a former vent of a volcano. Potassium-argon dating indicates that it is around 6.4 million years old, a similar age to Mount Gower and Mount Lidgbird on Lord Howe Island. After the eruption of the shield volcano, erosion saw the volcanic slopes form a submarine shelf. Ball’s Pyramid is in the centre of this shelf, forming a platform 20 km in length from north to south and around 10 km wide. The average water depth is about 50 metres. Lord Howe Island sits in the middle of a slightly larger shelf; the platforms of the two shelves are separated by a 500 metre deep canyon. Wave erosion will eventually truncate the volcanoes.

Both Ball’s Pyramid and Lord Howe Island are part of the Lord Howe Rise, which in turn is part of the submerged continent of Zealandia. Lord Howe Rise is a remnant of continental crust in the Tasman Sea, on the Australian plate.

The first successful climb to the summit of Ball's Pyramid was made by a team of climbers from the Sydney Rock Climbing Club on 14 February 1965. Another team, led by Dick Smith, reached the summit in 1979 and unfurled a New South Wales flag, declaring the island Australian territory. Climbing was banned in 1982 and in 1986 all access to the island was banned. In 1990, the policy was changed to allow some climbing under certain conditions.

Ball’s Pyramid was thought devoid of life until a scientific expedition led by David Priddel and Nicholas Carlile in 2001 discovered a colony of 24 Lord Howe Island stick insects (Dryococelus australis) under a single melaleuca bush 30 metres up the rock face. The species had not been seen alive for over 70 years. These insects are known as ‘land lobsters’ or ‘walking sausages’ and are 15 cm long; they are the heaviest flightless stick insects in the world. A pair of the insects was sent to Melbourne Zoo which successfully operated a breeding programme; over 700 of the insects exist today. Read more about these insects and the breeding programme here:
Image credit: Fanny Schertzer

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