The Strange Spine of New Zealand's White Island

Rocky Planet iconRocky Planet
By Erik Klemetti
Dec 12, 2012 9:43 AMNov 19, 2019 9:19 PM


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The strange new White Island dome, peering over the ridge towards a cold lake in the volcano's crater. The dome is ~20-30 meters across and may have been forming for the past two weeks. Image: GNS Science. A couple New Zealand volcanoes got updates from GNS Sciences on Wednesday, but the oddest of the pair was the news from White Island. The volcano had a small eruption in August during the "Big Kiwi Volcano Week" when White Island and Tongariro erupted and the pumice raft was discovered in the Kermadec Islands. That small event was the first explosive eruption at White Island since 2001 and since then, GNS Science geologists have been watching the island to see if it might be headed into a new period of unrest. This is especially important considering that tourists are still being taken to the island on a regular basis. However, that may change now that "hell hog" (as my wife called it; see above) was spotted in the crater. Now, that might be the strangest looking lava spine/dome I have ever seen. To give you a sense of scale, the GeoNet report on the spine says its ~20-30 meters across, so not that big. I'm not even sure how to describe it - the lava forming it has to be highly viscous and somewhat cool to form those strange spikes coming off the top. The color (yellows and reds) also suggests that the lava erupting has been pretty highly altered by hydrothermal gases (or that could have happened after the lava was extruded). Brad Scott from GNS Science said "in more than 30 years visiting White Island I've never seen anything like it." It is truly weird - not only because domes are fairly uncommon at White Island. The closest thing I can think of to this cold slug of lava is the famous whaleback plug that erupted during the 2004-08 eruptions at Mt. St. Helens. However, in that case, the dome was smoothed by the cold, viscous dacite lava dragging against the walls of the conduit. Here, it also seems like partially solidified, jagged lava was forced out of the conduit at the vent. This new activity has prompted GNS Science to raise the alert status at White Island to Level 2 with an Orange aviation code as new explosions could occur. It is a little disconcerting that tour operators said they noticed the dome two weeks agoand only now was GNS Science made aware of this new event. Even a small dome like this might suggest that new lava might be forcing its way up the conduit, getting rid of this cooler remnant lava that was in the way. Or worse, the plug could allow pressure to build behind it, leading to an explosive eruption (phreatic or magmatic). GNS Science also updated us on the activity at Ruapehu, where there is still concern that an eruption is likely in the works. Higher than normal temperatures have been observed under the Crater Lake at the summit of the volcano and Gill Jolly of GNS Science says that the conduit beneath the crater lake might be sealed at a depth of a few hundred meters below the lake. Any time a conduit might be partially or fully sealed, the threat of an explosive eruption increased because pressure from gases coming off the magma can build rapidly. Even so, the alert status at Ruapehu remains at Level 1/Yellow as GNS Science says that although the likelihood of an eruption might be high, it is not inevitable.

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