In late December 2014, an underwater volcano in the South Pacific Kingdom of Tonga erupted and sent a violent stream of steam, ash and rock into the air. The ash plumes rose as high as 30,000 feet (9 kilometers) into the sky and diverted airline flights.
Most new oceanic islands often wash away quickly within a few months. The island doesn’t have an official name, and is referred to as Hunga Tonga-Hunga Ha’apai after two older islands to either side.
But this island was different. One of our satellites that detects volcanic eruptions alerted our scientists who were very excited because this type of explosive, undersea eruption is rare. In fact, the new Tongan island is one of only three of this kind of volcanic islands in the past 150 years to emerge and survive. It’s now three years old.
Zooming in from Space
The baby island is also the first of its kind to emerge in the modern satellite era. This is really important since it’s difficult to send our researchers the South Pacific every month to see how the island has changed – which it did very rapidly, especially in the first six months. But satellites in space delivered monthly views which we used to make these high resolution, 3-D topographic maps. With these maps, we tracked the early life and evolution of the island in unprecedented detail.
In April 2015, we watched an isthmus bridge begin forming from the new island to the older island neighboring it to the east. Soft volcanic material, especially on the island’s southern side, was eroded by the ocean and deposited on the tail end, which grew and grew till it reached the other island. It’s about 1600 feet (500 meters) across, or the length of 5 football fields.
The erosive forces of the ocean broke down the southern wall of the crater lake in May 2015. We thought this might mean that the island wouldn’t last much longer because the ocean could now attack the interior of the island’s tuff cone. But in June, a sandbar formed, closing off the lake again and protecting the interior. The sandbar has been in place ever since.
Monitoring these changes of both erosion and growth, we now believe that the island will last from between 6 to 30 years!
Terranauts!
Why has the island survived for three years? What makes eroding it away harder than for other blink-and-you-miss-it oceanic islands that disappear into the sea after a few months? To answer these questions, we need rock samples.
Working with the Tongan government, we recruited two French citizens sailing around the world who were in Tongan waters in June, 2017, to go to the new island on our behalf. We treated them like astronauts and gave them instructions to take pictures and samples of the volcanic rocks at locations we could see from space along the coasts, the interior of the crater lake, and from the top of the tuff cone.
They did a fantastic job documenting each sample and where it came from, and then mailed the box of rocks back to our team at our Goddard Space Flight Center in Greenbelt, Maryland, where they are currently being analyzed. We believe that after the eruption, warm seawater mixed with volcanic ash to chemically alter it so that when it hardened into rock it was a tougher material. We’re excited to see if the rock samples confirm this.
Did these Martian volcanoes form in an ocean or lake? If they did, wet environments such as these combined with heat from volcanic processes may be prime locations to search for evidence of past life. We may not know until we arrive on the red planet, but by studying Earth’s landforms, we’ll be better prepared when we do.
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