THE COMPETITION BETWEEN THE TWO LARGEST VOLCANIC COMPLEXES IN THE WORLD.

Mauna Loa

ESA’s Proba-V mini-satellite captured this image of the largest volcano on Earth, Mauna Loa covers half the island of Hawaii. It remains active, having last erupted in 1984.
To the east is the very active Kilauea volcano, which has been erupting for over three decades. The island of Hawaii is made up of five volcanoes as a whole.
The summit of Mauna Loa is 4,169 meters above sea level and extends another 5 km under the sea. Its 75,000 cubic kilometres of volume depresses the adjacent seabed by another 6 kilometres.

Tamu Massif volcano

Sager began studying the Tamu Massif more than 25 years ago, the structure is located deep in the Pacific Northwest on the Shatsky Ocean Plateau.

The top of a hot mantle plume rises, decompresses, melts, and generates a large amount of magma in the crust, either on land or on the seafloor.
Several scientific papers in the 1990s, including one written by Sager, outlined and supported the idea of the mantle pen model to explain the creation of Shatsky and the Tamu massif.

In 2009, Sager and the International Ocean Discovery Program drilled at various points in the region and discovered solidified lava flows up to 23 meters thick, suggesting that the massif had been the product of gigantic eruptions.

To the team, it appeared that Tamu Massif was a giant shield volcano: a type of volcano created when lava erupts and builds up in layers, creating a vaulted structure that resembles a huge rock shield.
In this case, the Tamu massif would be the largest shield volcano in the world.

Magnetic signature of Mount Tamu

There appeared to be anomalies in its magnetic signature.
The Tamu Massif is located at the meeting point of three ocean ridges. Here, magma bubbles up, solidifies to form a new crust and moves outward from the ridge. As new crusts form at these ridges, a snapshot of the Earth’s global magnetic field is recorded.

The Tamu Massif is not a shield volcano. It appears that it is actually a huge body of oceanic crust 30 kilometres thick, four times the global average. We don’t know how this is possible, but it underscores that the rate of crustal production has exploded, again for unexplainable reasons.

The Shatsky ocean shelf is also covered with telltale magnetic bands, meaning that the ocean shelves are, according to Sager, formed by an increased type of seafloor expansion.

Essay about mantle convection