20 votes

Is the Mid-Atlantic Ridge a ridge or a trench?

Trench has a specific meaning in plate tectonics. It doesn't just refer to any valley; it specifically refers to the features formed at subduction zones by the flexure of the downgoing oceanic plate. ...
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  • 2,201
15 votes
Accepted

Are there seamounts as close as 100 m to the water surface and not inside any Exclusive Economic Zone?

Yes, there are many. According to the seafloor topographic data of ETOPO (1 arc second resolution), and the Exclusive Economic Zones (EEZ) database of marineregions.org. There are at least 157 ...
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14 votes
Accepted

Plate Tectonics: Is it possible to have an ocean-continent divergent boundary

The oceanic plates are themselves formed from the divergent boundary, so probably not. Even if a new rifting occurred exactly at the boundary, the result would eventually be that the ocean floor ...
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  • 5,896
13 votes

Are there seamounts as close as 100 m to the water surface and not inside any Exclusive Economic Zone?

Checking the Wikipedia page on underwater volcanoes and listing them by height, I think the best candidate is Vema Seamount. Vema Seamount is in international waters and its shallowest point is at 11 ...
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  • 14.7k
9 votes
Accepted

Why did it take so long to discover the volcanic nature of mid-oceanic ridges?

If it weren't for WW2 and the search for German submarines, the discovery of mid-ocean ridges might have waited until satellite based gravimetric mapping in the 1980s. It was the use of fine ...
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7 votes
Accepted

What is the tectonic explanation for parallel ridges in the Arctic Ocean?

The fact that these three features are parallel may be somewhat coincidental, although we can suspect that tectonic forces have influenced their morphology. The crust under the Arctic Sea is one of ...
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5 votes

How can linear oceanic ridges (like the East Pacific Rise) be explained by single point mantle plumes?

Hot spots and ridges are two different things. Hot spots stay in one place while the earth crust above them drifts and thus create a line of dormant volcanoes, they are a point features so to say. ...
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  • 766
5 votes

Is the Mid-Atlantic Ridge a ridge or a trench?

Let's clear up the terminology first: trench A trench, as @bon has described in their answer, is formed where tectonic plates move towards each other and one of the plates is subducted under the other....
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5 votes
Accepted

What is meant by intraplate volcanism?

The majority of Earth's volcanoes occur in plate boundaries. These can be at spreading ridges (green dots on the map) where they are mostly underwater, but sometimes are above the water (such as in ...
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  • 22.2k
5 votes

What is meant by intraplate volcanism?

Terms: Intraplate volcanism - as the name suggests it is volcanism within the plates rather than at plate boundaries. These are also known as hotspots. Ocean island basalt (OIB) - is the basaltic ...
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  • 133
5 votes

Divergent boundary and trenches between oceanic plates

The elevation of oceanic crust is controlled by Pratt isostasy, whereby hotter crust is elevated because it is less dense. Oceanic crust is produced at mid-ocean ridges and cools as it moves away from ...
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  • 2,201
4 votes

Why did it take so long to discover the volcanic nature of mid-oceanic ridges?

I think the U.S. Geological Survey has the gist of your answer -- prior to the mid-1900s, there wasn't enough seismological data to draw any conclusions: During the 20th century, improvements in ...
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  • 2,803
4 votes
Accepted

What is the geochemical source for the helium detected in deep Arctic explosive eruptions?

Helium is formed through the radioactive decay of uranium 238, uranium 235 and Thorium 232. A helium atom is an alpha particle that has collected electrons. The only way that helium is produced on ...
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  • 20.3k
3 votes

Are Helium 3 and 4 being produced by earth's core?

Are Helium 3 and 4 being produced by earth's core? tl;dr no. The paper you are referring to has major flaws in it. Claims that should not be in any respectable scientific journal such as: ...the ...
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  • 22.2k
3 votes

What are the parallel horizontal lines on Google's satellite images?

The yellow east-west trending lines (except possibly one) are transcurrent faults associated with mid-ocean ridges. They divide strips of ocean floor produced by segments of the ridge. A mid-ocean ...
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  • 3,028
2 votes

Why does the ocean floor look so scratchy?

If I am understanding the question correctly those straight lines may not actually be lines, they may be strips or bands and they are bands that are not actually there. The bands are a result of ...
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  • 1,178
2 votes

How can linear oceanic ridges (like the East Pacific Rise) be explained by single point mantle plumes?

hot spots help/control how spreading centers form but they are not what keeps them going. If you push on a thin amorphous material perpendicular to the surface they tend to crack/split at three ...
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  • 6,465
2 votes

What is meant by intraplate volcanism?

Intra = within/on the inside, so intraplate volcanism would be volcanism happening far from plate boundaries, usually hotspots. If you have trouble remembering intra- vs inter- remember international ...
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  • 6,465
1 vote

Why is the Lithosphere-Asthenosphere Boundary an Isotherm?

Reading this question, I'm not sure if you realize what an isotherm is - in this case, imagine peeling rock from the surface of the earth until you reached a temperature of 1300 degrees Celsius. Now, ...
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1 vote

Is the Mid-Atlantic Ridge a ridge or a trench?

A Graben/Rift valley is more attuned to divergent plate environment where as a Trench is mostly used and accepted when convergent plate activities is under discussion, other wise the two portray the ...
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1 vote

Plate Tectonics: Is it possible to have an ocean-continent divergent boundary

You May think of this situation as following: Consider an ocean-ocean divergent boundary and one of the oceanic plates (OP) is subducting below the continental plate (CP). Following shows such a ...
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  • 347

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