Day 46 Sailing through pumice 17/10/13

Oct 17 w Kermadec Isl

Yesterday I was becalmed and  just making head way at about 1 knot. We have been drifting through this patch of material which I will describe. At first I thought it was styrofoam because of its yellowish colour and the fact that it was mainly in small piece. Some are the size of a loonie, (Canadian one dollar coin), others as small as a penny along with larger bits and all floating fairly high in the water. This material has gooseneck barnacles hanging from some of the larger pieces, so I imagine it has been out here for some time. I managed to scoop up several pieces with a sauce pan and to my astonishment discovered it is pumice.  And there’s acres of this stuff. It’s not as thick as a carpet but scattered about randomly and definitely in a significant enough concentration to get my attention. I am going to take it down to my lab and run some tests on it and I will report back on my findings.

I’ve been drifting through it for 6 hours now and it’s still coming over the horizon. What is astonishing is the amount of wildlife on a single piece as big as a baseball – gooseneck barnacles, small crabs, and black centipedes. The gooseneck barnacles have beautiful white shells with a very thin bright yellow eye liner around the edge and the neck, in contrast, is black and looks like it belongs to a rugby player.

Gooseneck_barnacle wikimedia

photo courtesy: wikimedia commons

They are only about an 1  1/4″ inches long and 3/4 “wide and shaped like a small spoon. The centipedes are black with furry legs on each side of their bodies which are about 1” long. The small crabs are tortoise shell with miniature white pinchers and they are about the size of a dime. There seems to be a coral covering the pumice in a very delicate tiny pattern and grey in colour. I broke a piece of the pumice off easily with a pair of pliers. It’s very light and filled with air pockets which is what gives it its buoyancy. The one piece I picked up had three gooseneck barnacles, one crab and two black centipedes. I imagine if I was sailing through this acreage of pumice I may have heard it on the hull as I pass by. But at the moment I only wish I was sailing through this unusual phenomena. Nonetheless I’m glad to be going slow enough to be observe it closely.

The Kiwis have found me on the air.  The afternoon ham radio show is now an hour long. I spoke to ZL2MS Peter from Napier who was the first Kiwi ham I talked to when I sailed by last time. He also knows all about the source of the pumice. I’m going to speak to John ZL2DD in a few minutes. At the moment there are five kiwi hams I speak with every night. They are all very nice guys.

Then … another piece of the pumice story unfolds in this email from ham radio operator Peter in Napier who sent the following email. 

“Hi Glenn
I talked to you on 20m at 0400 UTC 17 October. You described floating pumice that was encountered during the day’s sailing. It is likely the pumice from an undersea volcanic eruption located near the Kermadec Islands. The eruption occurred in July 2012. The
estimated area of sea covered by the floating pumice was about 25,000 square kilometres. The area spotted initially by overhead aircraft measured about 460 km long by 55 km wide. Pumice drifts up to 3 metres deep were encountered by vessels. Hope to contact you on the radio again soon.”

A Google search of the Kermadec Islands produced a link to an Earthquake Report  site. It reported a magnitude 5 earthquake at the Kermadec Islands on October 15th. 




  1. Hi Glenn,

    We’re enjoying your daily reports. Can you tell me your ham freq and time?


    Doug Cole

  2. Fascinating!! Leaves me wondering how tiny crabs make their way from a shoreline to this floating island home! I guess it only takes two to establish a colony!
    Fair winds mate!

  3. Nick Goodall says

    Hi Glen,

    Give this a try: Try taking a bit of pumice and driving your fingernail into it to try and break some of the tiny gas bubbles. While you are doing this, hold the pumice up to your nose and give it a little sniff.

    The gas that is trapped in pumice that makes it float is produced during a volcanic explosion and it’s usually pretty stinky. It’ll probably smell strongly of sulpher. Actually it pretty much smells like a nasty fart! I don’t know this is the kind of entertainment you are looking for, but if you’re curious, give it a go and report back.

    Have fun!

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