Questions tagged [subduction]

The process where denser oceanic crust is forced under continental crust. These convergent boundaries are sites for volcanic arcs.

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2answers
149 views

How does a subduction zone form mountains?

When an oceanic plate goes under a continental plate are the resulting mountains a result of the melting and then rising of the oceanic plate or are the mountains formed by the continental plate being ...
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Are the Olympic Mountains (in Washington state) geologically unique?

So it is my understanding the Washington's Olympic Mountains are basaltic mountains. The reason is that they formed from the upthrust of Ocean crust rather than continental crust as the Farallon plate ...
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1answer
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Does subduction of continental crust happen at continental-continental convergent boundaries?

What exactly happens at a continental-continental (cc) convergent boundary? I read myself through the web for the last few days and what I came up with is that such a boundary will start as an oceanic-...
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1answer
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Is there a name for subduction boundaries at the North of Australia?

I know the ridge at the South of Australia is named Southeast Indian Ridge. I would like to know if there is a geological name for the three subduction branches that cross indonesian zone, at the ...
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1answer
243 views

Is it ever possible for an continental plate to subduct under an oceanic plate?

It is well known that oceanic plates subduct under continental plates. This may be attributed to the plate's age and density, plus the water on top of it. So I was wondering if it is ever possible for ...
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Can the process of subduction flatten the shape of a subducting plate relative to the plate it's going under?

There's something I’m still not quite getting about why island arcs are arcs. In the examples I’ve seen, the subducting plate is compared to a knife slicing across the surface of an orange - but it ...
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1answer
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Volcanoes in the Alps and Himalayas and the subduction of Tethys Sea

Geologist have theorized that the Tethys Sea subducted under Eurasian plates. But where are the volcanoes that would have resulted due to this? Where are the volcanoes in the Alps and the Himalayas?
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Megathrust earthquakes on subduction zones

I am a beginner in geology and earthquake studies, and learning about subduction zones recently. Question is: do large earthquakes (sometimes referred to as megathrust quakes) occur on any point in ...
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2answers
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How does 10mm/yr of plate subduction provide enough material to create eruptions?

If the convergent boundary is only consuming 10mm of oceanic crust per year, it "seems" like that would provide insufficient material to cause the level of eruption generally observed. I am making the ...
5
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1answer
83 views

Is the concept of seismogenic zone still relevant after the 2011 Japan earthquake?

The concept of subduction seismogenic zone, where megathrust seisms occur in a layer between an upper and a lower limit is well documented in the 1990/early 2000 literature : Some example : Pacheco,...
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1answer
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Why are oceans so deep?

Some areas of oceans are about 11 km deep. Is it because continental plates were moving away because of troughs in the middle from where new rock is formed? If so, why did it become deep? If not, what ...
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1answer
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Identifying serpentinite reworked during high-T metamorphism

What kind of mineralogy results when a serpentinite is reworked during high-T or UHT metamorphism? I am envisaging a possible scenario where an obducted ophiolite terrane is buried and metamorphised ...
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Has an entire plate ever subducted?

We know that plates can subduct, causing one plate to be pushed into the core by another. As the plates move, the subduction continues, pushing one plate under the other. If this process continues, ...
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1answer
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What geological processes would 'restart' subduction processes?

According to the Science Daily article Plate Tectonics May Grind To A Halt, Then Start Again (Carnegie Institution), one main aspect of the research being presented is the hypothesis that suggests ...
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534 views

What are the geological mechanisms for sea floor spreading in the Bismarck Sea?

The North and South Bismarck microplates (north east of Papua New Guinea) are separated by a ridge of sea floor spreading, as described in Oregon State webpage as The tectonics in this part of the ...
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What geological mechanisms result in the great depth of the Mariana Trench?

According to the Mariana Trench Oceanography page is at a maximum depth of is 11,033 meters (36,201 feet) The 'Challenger Deep' being the name of the deepest point. I understand that it is a ...
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182 views

Geometrical differences of subduction zones

I am looking for geometrical differences in subduction zones. What are the differences, in dip, curvature of the interface, thickness of the plates etc.? There are differences between the Chile and ...
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When a tectonic plate subducts, does any of the subducted material melt, or is it just the mantle above the subducted slab that melts?

I know that water released from oceanic crust causes melting of the mantle in subduction zones, but does any part of the subducted slab melt as well - such as the sediments on the slab or the basalt? ...
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Is a billion years of Earth's history missing?

Appears that a 4.4 billion-year-old crystal is oldest piece of Earth, and the crystal's chemistry -- specifically, the ratio of oxygen isotopes within it -- suggests that the temperatures on Earth 4.4 ...
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Exhumation of blueschist

Blueschist has a mineral assemblage such that it must have formed at high pressures and low temperatures. It must therefore form in subducting slabs (and I believe this correlates with the locations ...
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Why does a subduction zone produce a serpentinization diapir rather than volcanism?

The classic Troodos Ophiolite in Cyprus has been uplifted by a 'serpentinization event'. Upper mantle (peridotite) has been serpentinized creating a buoyant diapir. This has uplifted the ocean crust ...