A cluster of earthquakes can be a geologic force of great proportions. Over the course of two days in late July, the Kermadec Trench experienced more than 157 earthquakes with magnitudes between 3.0 and 4.8. These tremors are associated with the eruption of an underwater volcano called the Havre volcano which is located halfway between New Zealand and Tonga. Classified as a caldera volcano, the Havre seamount remains mysterious to scientists and was not thought to have erupted before.
Then last week, a New Zealand Navy ship ran into a remarkable sight: a floating island of pumice stretching over 26,000 square kilometers (nearly the size of Belgium). Scientists at the Laboratoire de Volcanologie in Tahiti say this “raft” was created by the recent eruption of the underwater Havre volcano. It likely produced the golf-ball-sized pumice rocks as it spewed magma into the deep Pacific Ocean, but the very lightweight stones have since floated several hundred kilometers from their volcanic source.
It looked like a floating ice shelf, according to Naval Lt. Tim Oscar, and it extended beyond the reach of the ship’s spotlight as the HMNZS Canterbury passed through the pumice buoyant on a calm evening last week. The rocks are so porous that they can ride the waves for miles and pose no danger to ships. Lt. Oscar described it as the “weirdest thing” he had seen during his 18 years at sea.
Havre was one of three recent eruptions in the region, along with White Island off the west coast of New Zealand and Mount Tongariro, which spewed rock and ash on New Zealand’s North Island, having awakened after lying dormant for 115 years.
NASA satellite images are being used to correlate the plumes of smoke and ocean color changes associated with the Havre undersea eruption and the creation of the pumice raft. Next up scientists will head out in research vessel to take samples of the pumice stones and map any new changes in the seafloor near the volcano. Stay tuned for more explosive activity!
Main image credit: NASA Earth Observatory