Haystack Island
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  Haystack | |
| Geography | |
|---|---|
| Location | Investigator Strait |
| Coordinates | 35°19′19″S 136°54′26″E / 35.32191°S 136.9071°E |
| Length | 500 m (1600 ft) |
| Width | 120 m (390 ft) |
| Highest elevation | 43 m (141 ft) |
| Administration | |
Australia | |
Haystack Island is an island located in Investigator Strait off the south coast of Yorke Peninsula in the Australian state of South Australia about 6 kilometres (3.7 miles) south-west of Stenhouse Bay. Since 1972, it has been part of the Althorpe Islands Conservation Park.
Haystack Island is about 6 kilometres (3.7 miles) south-west of Stenhouse Bay. It is described as ‘a narrow wall of sheer cliffs, undermined, indented and marked by fresh scars and rockfalls’ and that ‘has been eroded to a series of tall lobes connected by thin necks of rock that narrow to an almost knife-edge ridge’. It is surrounded by a ‘fringing wave-cut reef’. The island is about 500 metres (1,600 feet) long by a maximum width of about 120 metres (390 feet) and with the tallest lobe having a height of 43 metres (141 feet). Its long axis is aligned in a north-west to south-east direction.[1][2]
Access is reported as best done in calm seas and that the summit ridge can be reached from the island’s east coast via a rubble cone of rubble, taking care when climbing the slope’s ‘loose and crumbling’ surface. A survey carried out in 1982 by the responsible government agency used a helicopter to access the island’s summit.[1][3] A number of sources consider Haystack Island along with the Althorpe Islands and Seal Island to be a group of islands known as the Althorpe Islands Group.[4][5][6]
Formation, geology and oceanography
Haystack Island was formed about 7350 years ago after sea levels rose at the start of the Holocene thereby separating Yorke Peninsula from Kangaroo Island.[7] Haystack Island consists of a seam of Bridgewater Formation calcarenite that sits on a largely submerged ridge of Gleesons Landing Granite.[6][8] Haystack Island rises from a depth of 20 metres (66 feet) within 300 metres (980 feet) from its southern shore.[9]
