December 19, 2013

Pumice floats ashore.

Pumice stone is a volcanic rock which is currently littering our local shoreline big time. 

Some pieces are as big as melons but most are the size of kids' marbles or your meal time legume. When I say littering -- there is heaps of the stuff, mounded high at the high tide line.

Ironically, it comes from volcanoes a long way offshore. Vulcanologists can relate any piece of pumice to its eruption-of-origin but we are generally talking about the product of activity in far off Samoa and other mid Pacific locales where the hills will go 'boom!' . 

How long it takes to get here may be of interest but the killer fact is that we live in cooee of Pumicestone Passage which is so named after the phenomenon by Matthew Flinders way back in 1799.


1799 must have been a good year for floating pumice because it isn't usually under our feet... and being a very soft rock(you can pull it apart with your fingers) it doesn't hold itself together long term once ashore.

Here on the western edge of Moreton Bay we are a dumpster for retired pumice coming to rest according to a time table of its preference.

But why the pumice should come ashore all at once is interesting is it not? Why so much pumice now when we aren't usually pumiced? 

It turns out that 'our' pumice is debris from the largest pumice raft in 50 years and is a product of an under sea eruption 800 km off the coast of New Zealand in the Kermadec Islands.
The 2012 Kermadec Islands eruption was a major undersea volcanic eruption that was produced by the previously little-known Havre Seamount near the L'Esperance and L'Havre Rocks in the Kermadec Islands of New Zealand. The large volume of low density pumice produced by the eruption accumulated as a large area of floating pumice, a pumice raft, that was variously estimated to be between 7,500 and 10,000 square miles (19,000 and 26,000 km2) in surface area. [Source]
So if you want to scrape the flesh of your heels as folk are want to do with a pumice stone, say no more, the stuff is here for the taking.

More about this pumice raft:

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