Sunday, 1 September 2019

Tonga comes to visit... again?

The effects of Tongan undersea volcanic eruptions are not the first thing you'd think of when enjoying the summer weather on a sandy beach at Kingscliff, Byron Bay or Port Macquarie. But 6 years ago, in 2013 there was a direct reminder of a volcanic eruption of the the undersea volcano the Havre Seamount. This reminder was pumice rock washed ashore from an eruption which took place about 6 months previously. You can read more about it on the blog post I wrote at the time. It looks likely a very similar thing is going to occur in the next few months.

In mid August this year (2019) it was observed that a massive 'raft' of pumice rock was floating west of Tonga. A small island called Fonualei showed evidence of recent activity, with steam and fresh pumice in the area. The extent however of the eruption went unnoticed until a sailing boat sailed through a huge pumice raft. ABC News has a great video of what sailing through the raft looked like.
Photographs from passenger aircraft and also some satellite pictures have shown that the size of the eruption must have been huge. The Island of Fonualei was active but clearly not the main location of the eruption. We'd all be very aware of the eruption if it was Fonualei erupting the volume of rock obvious from the satellite. A formal but short report on the eruption by the Smithsonian Institute can be found here.

Given that the prevailing currents and winds will direct this pumice onto the coast of Australia it is something to look out for. Biologically it is interesting too. Fresh pumice washed up on the shore can transport various sea creatures. This is because pumice makes a great home given its porosity.
Not much more to add, except a prediction. I don't know how good it will be but I guess that come mid summer we will see pumice from Tonga washing up on the beaches of NSW and Queensland.

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