The Hippo


Apr 23, 2019








Bill Menke atop Carter Dome in Coos County. Courtesy photo.

Baby volcano in NH?
New research suggests state sits atop ‘upwelling’ of magma

By Ryan Lessard

 Could the Granite State be sitting atop a slowly rising reservoir of molten rock? Some new science suggests the answer is yes, and it could also be contributing to some of the state’s unique geological features, like the height of our mountains.

If their findings are correct, scientists say a volcano could form in New Hampshire, but fear not; it won’t happen anytime soon. In fact, it’s likely the rising magma will not come close to the Earth’s surface for several hundreds of millions of years. 
So we’ve got some time.
Still, some 120 miles below us, an upwelling like this could explain certain natural phenomena and maybe even lend the White Mountains their formidable altitudes. Mount Washington is the tallest mount in the Northeast, after all. 
To Bill Menke, a geologist with the University of Columbia’s Lamont-Doherty Earth Observatory, a feature like New Hampshire’s 7,000-footer was an early clue that something was up — or down, as it were.
“I have been interested for many years about what makes New Hampshire the special places it is,” Menke said.
Other clues included spikes in helium found in the state’s groundwater, something a magma upwelling would explain, overhot underground temperatures, and the occasional earthquake.
“The fact that we have earthquakes in New England is somewhat anomalous because we don’t have faults,” said New Hampshire state geologist Rick Chormann.
Some of these features have been known by scientists for decades. They dubbed it the Northern Appalachian Anomaly. But they believed the NAA was an effect from a hotspot that passed under this area of the continent.
“The prevailing theory for why New Hampshire looks so different than other parts of the Appalachian Mountains had to do with this hotspot that passed New Hampshire about 100 million years ago,” Menke said. 
The hotspot is known as the Great Meteor hotspot, named after the ship that discovered it.
“It has nothing to do with a meteor in the astronomical sense.” 
As the surface of the Earth has shifted over the upper mantle, a pock-marked undersea trail has revealed the presence of the ancient hotspot, and a line can be traced back from its current location in the Atlantic Ocean to New Hampshire and Quebec. 
But the high underground temperatures, helium fizz and tall mountains have a present-day phenomenon at work behind them, Menke said.
By studying data from the Transportable Array seismograph network and his own sensitive instruments, he was able to infer the presence of a current upwelling 250 miles across and 100 miles thick from top to bottom under central and southern New Hampshire.
Chormann says this may settle a longstanding debate about the formation of the White Mountains and the present-day NAA.
“Not everyone agrees that that active magmatic episode [which created the White Mountains] was related to the hotspot,” Chormann said.
He said the White Mountain batholith (an upward injection of magma deep inside the crust) was created in the Jurassic period between 160 million and 180 million years ago, hardened into rock and became exposed over millennia of erosion, transforming into the mountains we know today.
Instead of owing that injection to the hotspot, it’s possible this upwelling has been around just as long. Menke believes it’s caused by the flow of upper mantle beneath our continent forcing up magma on the other end, like the bubbling water in the wake of a boat.
He’s found similar phenomena in Virginia and parts of Louisiana. 

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