A megavolcano found at the bottom of the Pacific Ocean is being reported as the largest single volcano on Earth. Tamu Massif, as the megavolcano is called, may be as voluminous as Olympus Mons on Mars, which is regarded as the Solar System’s largest known volcano.
Tamu Massif, the inactive volcano, was previously thought to be a string of volcanoes rather than one enormous feature. It is part of an underwater mountain range called the Shatsky Rise, which covers an area as large as California state in the US. Found close to the east of the coast of Japan, Shatksy Rise formed some 145 million years ago as huge amounts of magma flowed onto the ocean floor at a point where three microplates of Earth’s crust meet.
While Olympus Mons is much taller (>25km) than Tamu Massif (about 4km), its base is smaller. Massive lava flows would have rapidly flowed along shallow slopes to create Tamu Massif, which has a 650km-wide base, nearly as big as New Mexico in the US. Volcanoes created entirely due to such lava flow are called shield volcanoes because they resemble a warrior’s shield.
The volcano’s structure is described in the journal Nature Geoscience by scientists from the US, the UK and Japan. Tamu Massif is named after Texas A&M University, where the lead researcher William Sager is based.
Although rocks from Tamu Massif had previously been identified as volcanic crystallised lava, its size made geologists believe it was the result of many volcanic eruptions that may have occurred over a period of many millions of years. Now it seems that this may have been closer to a distinct but enormous flood of lava.
To verify that hypothesis Sager’s team collected new samples and data aboard an ocean-going science research vessel called Marcus G. Langseth. They drilled samples from the ocean floor, and poked Tamu Massif with seismic waves, measuring the response using seismometers. They were able determine whether the rocks may have come from different eruptions. From all the new data they acquired it seems that lava flow emerged from a single central magma vent.
Time on such research vessels is expensive and this report is first of its kind looking at large underwater volcanoes. Much of Earth’s ocean floor remains to be thoroughly explored. This makes Sager believe that there may be even bigger volcanoes out there.