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Apples and Oranges Applied to Volcanoes

September 13, 2013, 6:14 PM HST
* Updated September 19, 9:09 PM
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An underwater mountain that made the news recently in one way can’t hold a candle – and definitely not a lava fountain – to the Big Island’s Mauna Loa.

In their latest Volcano Watch column, scientists from Hawaii Volcano Observatory say recent news reports calling Tamu Massif the world’s largest volcano are misleading.

“The volcano off the east coast of Japan, which made the news last week – touted as the largest volcano in the solar system – last erupted 146 million years ago, possibly around the time the Pacific Ocean Basin was first formed,” the column said.

Mauna Loa, on the other hand, is definitely the world’s largest “ACTIVE” volcano, HVO noted.

The mountain making up most of the southern part of the Big Island has erupted 33 times in the past 170 years and future eruptions are a certainty, scientists at the US Geological Survey facility said.

And the next eruption may not be too far off.

Coincidentally, just as those reports about Tamu Massif were circulating, HVO’s seismic equipment was recording a three-day-long swarm of earthquakes below Mauna Loa’s summit.

Although the strongest tremor was only of magnitude 2.4, the swarm occurred in the same region as previous quakes which preceded the volcano’s 1975 and 1984 eruptions.

HVO described the swarm as a “possible, but not definite, precursor to the next eruption of Mauna Loa.”

Tamu Massif made the news after scientists said that recent studies indicated that what was once thought to be a group of undersea mountains known as the Shatsky Rise is apparently one big, extinct volcano. But the researchers also caution that so far only a small portion of Tamu Massif has been investigated.

The rise covers 120,000 square miles, while the base of Mauna Loa is about 2,000 square miles.

But does a footprint really dictate largeness? For example, who pays much attention to Lebron James’ shoe size?

We’re with HVO on this one.

Even the science journal Nature, which described 13,000-foot-tall Tamu Massif as the “largest single volcano on Earth,” acknowledges that Mauna Loa is much taller, rising more than 29,000 feet from the ocean floor.

But when it comes to height, the above pale in comparison to the solar system’s reigning giant, Mars’ 84,000-foot-tall volcano Olympus Mons.

But that volcano has a few advantages our own Mauna Loa doesn’t: It developed under Mars’ lower gravity, and, unlike Mauna Loa, keeps growing on the same spot.

Mauna Loa, like her sister mountains, developed on a tectonic plate in continuous movement across the stationary, Hawaiian Islands-producing hotspot.

Scientists say Olympus Mons is so big that the Hawaiian islands from Kauai to the Big Island could fit inside.

There’s an idea. Let’s compare the Mars monster to all of the magma from all those islands and the rest of the Hawaiian chain that over eons have eroded from tall mountains to coral atolls. And might as well throw in the earliest Hawaiian islands located in the Emperor Seamounts, mountain tops that are now below the ocean’s surface.

It seems fairer than calling a something a volcano when it hasn’t seen fresh lava in 146 million years.

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