Ōrākei Basin is one of the volcanoes in the

Auckland volcanic field The Auckland volcanic field is an area of monogenetic volcanoes covered by much of the metropolitan area of Auckland, New Zealand's largest city, located in the North Island. The approximately 53 volcanoes in the field have produced a diverse a ...

in the North Island of

New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island count ...

. It has an explosion crater around 700 m wide, with a surrounding tuff ring. The present basin is slightly larger than the original

maar A maar is a broad, low-relief volcanic crater caused by a phreatomagmatic eruption (an explosion which occurs when groundwater comes into contact with hot lava or magma). A maar characteristically fills with water to form a relatively shallow ...

crater.

Geology

After eruption at least 83,000 years ago, it became a freshwater lake that had an overflow stream in the vicinity of present Ōrākei Rd bridge. As sea level rose after the end of the Last Ice Age, the lake, which by then had shallowed to a swamp, was breached by the sea and has been a tidal lagoon ever since. A tidal lagoon, it is popular for watersports.

History

A railway line (the

North Island Main Trunk The North Island Main Trunk (NIMT) is the main railway line in the North Island of New Zealand, connecting the capital city Wellington with the country's largest city, Auckland. The line is long, built to the New Zealand rail gauge of and ser ...

, branded as the Eastern Line for suburban services) runs through the north side of the basin. The railway runs along a causeway embankment which was constructed in the 1920s and created a barrier between the Ōrākei Basin and the rest of the

Waitematā Harbour Waitematā Harbour is the main access by sea to Auckland, New Zealand. For this reason it is often referred to as Auckland Harbour, despite the fact that it is one of two harbours adjoining the city. The harbour forms the northern and easter ...

. This allows for the basin to be kept full, even during surrounding low tides. The embankment has control gates to allow the scheduled flushing and re-filling of water in the basin. Orakei Basin panorama

References

*''City of Volcanoes: A geology of Auckland'' - Searle, Ernest J.; revised by Mayhill, R.D.; Longman Paul, 1981. First published 1964. . *''Volcanoes of Auckland: The Essential Guide''. Hayward, B.W., Murdoch, G., Maitland, G.; Auckland University Press, 2011. *''Volcanoes of Auckland: A Field Guide''. Hayward, B.W.; Auckland University Press, 2019, 335 pp. .

External links

Photographs of Orakei Basin
held in Auckland Libraries' heritage collections. Auckland volcanic field Waitematā Harbour Ōrākei Local Board Area Maars of New Zealand {{Auckland-geo-stub