Friday, October 1, 2010

Pumic Rock - 1800 Years Old

This rock was taken from Lake Toupo ( from a volcanic moutain to a lake ) which is situated in the volcanic heart of the North Island of NZ. Lake Taupo region is home to New Zealand's largest fresh water lake, fascinating geothermal areas and the famous Huka Falls.

Pumice rocks are igneous rocks which were formed when lava cooled quickly above ground. You can see where little pockets of air had been. This rock is so light, that many pumice rocks will actually float in water. Pumice is actually a kind of glass and not a mixture of minerals. Because this rock is so light, it is used quite often as a decorative landscape stone.

The Taupo Eruption 1800 years ago

The most recent eruption of Taupo was about 1800 years ago. Although the precise year of eruption is not know, evidence from trees preserved at Pureora Forest suggest it occurred in late summer. The Taupo eruption was a complex series of events. The first phases of the eruption produced a series of five pumice and ash fall deposits over a wide area of the central North Island, especially east of Taupo and beyond Napier into Hawke Bay. The eruption culminated with a large and very energetic pyroclastic flow that devastated an area of about 20,000 square kilometres and filled all the major river valleys of the central North Island with pumice and ash. These pumice deposits can still be seen today and many of the major rivers in the North Island carry large amounts of this pumice when in flood. Rounded pumice found on the beaches of the North Island have come from this eruption.

The Taupo eruption took place from a line of vents near the eastern side of the modern lake. At the beginning of the eruption, the vent was clear of the lake as there is minimal evidence for water involvement with the erupting magma. However the lake eventually breached the vent and several stages of the eruption were dominated by mixing of the magma and lake water, with fine ash being formed. Fall of this ash was accompanied on occasion by heavy rain.

For more info on Toupo Volcano visit :

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