What are these underwater mountains in the North Atlantic?

General Questions
#1

I was looking at a map of a shipwreck off Nantucket and saw to the south what looks like a range of underwater mountains, or an archipelago of underwater islands, off the continental shelf. Google isn’t coming up with any names or descriptions for me; it’s not the Mid-Atlantic Ridge.

Here’s one point on the range

If the link doesn’t work, it’s visible on google maps satellite view, roughly 500 miles east of the Delmarva peninsula, 350 miles south of Nova Scotia and around 500 miles north of Bermuda. It seems to extend several hundred miles.

#2

Those are seamounts. They’ll be the remains of undersea volcanoes. At some point there will have been a hotspot underneath and the magma upwellings create the volcanoes as the plate passes above it. Much like Hawaii. The hotspot started under the continental USA (that plate is moving west) and extinct volcanoes like Mt Ascutney may be related. And the hotspot may be coming back - in several million years or so.

#3

Specifically, it’s the New England Seamount chain, part of theGreat Meteor hotspot track

#4

As an aside, the chain has nothing to do with meteors, but was named after the German research vessel Meteor which discovered it between 1925-1927. The largest seamount was named Great Meteor Bank and the name extended to the chain.

#5

I am not a geologist, but I think perhaps this is turned around a bit. Or I am just not understanding Quartz’s post-more likely. The magma under Vermont talked about in the referenced article is unlikely to have caused the seamounts. As has been mentioned, the continental plate is moving generally west. In the past both the continent and the seafloor where the seamounts are were further east. The Vermont magma isn’t moving with the plate and is probably stationary. So it has never been under the seamounts. What is likely is that another magmatic upwelling occurred near the mid-ocean ridge-well to the east of the current seamounts-and caused volcanoes. Just as in the case of Hawaii, the seafloor spread away from the hotspot producing a line of volcanoes in the seafloor. That is what you are seeing. As to whether that hotspot is still generating volcanoes on the seafloor-apparently not. Perhaps the hotspot did some (three dimensional) traveling itself and moved west to be under Vermont. Or it just sank or cooled and another hotspot grew under Vermont. Who knows and how could one tell?
The takeaway is that the seafloor spreading is moving the upper crust along to the west and a hotspot created these volcanoes much further out to sea then their current location.

What I think is happening is that there are two hotspots, one that created the Great Meteor line from Hudson Bay to the mid-atlantic ridge and the “new” one under Vermont.

#6

The youngest activity for the Great Meteor hotspot is around ten million years ago. As these things go, that might just be a dormant patch - if you follow the entire track, there are several gaps. It may be the nature of that particular hotspot.

#7

Ignorance fought! Thank you! Coincidentally I recently visited the other end of the Great Meteor track, in the Monteregian Hills and White and Green Mountains.

Here are a couple of informative NOAA links
https://oceanexplorer.noaa.gov/explorations/03mountains/background/geology/geology.html
https://oceanexplorer.noaa.gov/explorations/05stepstones/background/geologic_history/geologic_history.html

Also helpful to know the origin of the name “Great Meteor”; without that info I would have been very puzzled imagining an impact like the Chicxulub crater.

#8

I’m not understanding something. The majority of the hotspot track is west of the Mid-Atlantic Ridge, but the Great Meteor seamount is to the east of that ridge. That ridge is where the sea floor spreading is happening. The crust to the west is moving westward, that to the east, eastward. So how did the hotspot cross the ridge? The only way this could happen is if the crust to the east of the ridge is also moving west. Is that the case?

#9

Yes. The ridge, which is part of the boundary between the plates, itself has drifted westward, and has over-ridden the hotspot.

#10

What causes the ridge to drift?

#11

I had an epiphany about this several years ago, when trying to figure out how all the globe’s plate movements fit together (I started by realizing the North American and Eurasian plates must have a “hinge point” in northern Siberia, and sure enough they do).

The upshot is: relative plate movements are occurring at two or even three DIFFERENT SCALES. At the biggest scale, there’s basically a bunch of southern plates that are subducting under a couple of huge northern plates. Then, within these two big zones, there are the various relative plate-to-plate movements we’re more familiar with.

Remember, movement is relative. If I walk down the aisle of an airplane, am I moving two miles an hour south, or five hundred miles an hour east? Both.

(Another example of this is how a Pacific spreading center “jumped” into the continental crust of North America, generating a new intra-continental rift — the Sea of Cortez/California).

#12

Actually, at the biggest scale of all, it’s just one spherical shell that’s subducting under/colliding into itself – imagine a thin ball, with a slice through about half of it, and start tucking it under itself along that slice.

One end of the slice – a “hinge point,” where the relative movement begins (or ends) – is in the middle of the Atlantic Ocean, at the furthest western trace of the grand Tethys Sea closure (which begat Indonesia, the Himalayas, the Mediterranean…): the African/North American/Eurasian “triple junction.”

#13

*The Terceira Rift, the world’s slowest spreading center – and now you can see WHY it’s the slowest.