Sentences with phrase «at subduction»

[4] The ocean's influence extends even to the composition of volcanic rocks through seafloor metamorphism, as well as to that of volcanic gases and magmas created at subduction zones.

The human fossil fuel CO2 emissions spike is more like an asteroid impact than the slow degassing of CO2 from metamorphic decarbonization of carbonate rocks at subduction zones by the slow grinding away of plate tectonics.

Megathrust earthquakes are the most powerful types of earthquake, occurring at subduction zones - where one tectonic plate is pushed beneath another.

The research programme will investigate the geological processes that occur at subduction zones - regions of the Earth's crust where one tectonic plate descends beneath another, generating volcanoes and earthquakes.

Faster sea floor spreading, presumably associated with more volcanic activity at subduction zones, and / or other increases in volcanic activity or geologic outgassing, or faster oxidation of exposed fossil organic C (as in shales)-- greater geologic CO2 emissions (I think another way of looking at the inorganic part is that any given region of sea floor has less time to accumulate carbonate minerals from chemical weathering, so that C reservoir could shrink while others, including the atmosphere, can grow).

Kattenhorn and Prockter saw ice volcanoes on the overriding plate, possibly formed through melting and absorption of the slab as it dove below the surface, and a lack of mountains at the subduction zone, implying material was pushed into the interior rather than crumpled up as the two plates mashed against each other.

On Earth, as new surface material forms at mid-ocean ridges, old material is destroyed at subduction zones, which are regions where two tectonic plates converge and overlap as one is forced under the other.

The volcanoes are formed by conditions at the subduction zone where one of Earth's largest tectonic plates, the Pacific Plate, dives beneath the Australian Plate.

A plate can bump up against another plate at a fault zone, or dive beneath one at a subduction zone.

Lead author of the study, Dr Caroline Eakin, Research Fellow in Ocean and Earth Science at the University of Southampton, said: «The process of consuming old seafloor at subduction zones, where great slabs of oceanic material are swallowed up, drives circulation in the Earth's interior and keeps the planet going strong.

The preliminary results from the Cascadia Initiative include a report of previously undetected, small earthquakes offshore, and seismic imaging that reveals new offshore structures at the subduction zone.

Uplift is common along the coastlines of continents at subduction systems worldwide (e.g., Kamchatka, Japan, New Zealand and Papua New Guinea) with rates of vertical uplift accrued over the last 10,000 years being generally higher — up to ten times more than for time intervals larger than 125,000 years.

At subduction zones such as these, an oceanic tectonic plate sinks (subducts) into the Earth's interior, the mantle.

In fact, lava emerging from hotspot volcanoes is known to differ chemically and isotopically from lava from other volcanoes, such as those erupting at subduction zones where Earth's crust dives into the upper mantle.

Most earthquakes are said to occur at subduction zones or along faults in tectonic plates.

One hint of weak coupling at a subduction zone is the presence of serpentinite — a mineral formed when seawater carried down by a descending plate reacts with mantle rock.

The pressure difference could be caused by hot, partially molten rock piled up beneath mid-ocean ridges or beneath the cooling plates diving into the earth at subduction zones, the authors write.

Three basic forces are believed to drive oceanic plate movement: plates are «pushed» away from mid-ocean ridges as new sea floor forms; plates are «pulled» as the oldest parts of the plate dive back into the earth at subduction zones; and convection within the asthenosphere helps ferry the plates along.

Not exact matches

They simulated earthquakes with magnitudes between 9.0 and 9.6 originating at different locations along the Aleutian - Alaska subduction zone, a 3,400 - kilometer (2,113 - mile) long ocean trench stretching along the southern coast of Alaska and the Aleutian Islands where the Pacific tectonic plate is slipping under the North American plate.

Scientists have long wondered what accounts for that precipitous dive, and why the massive earthquakes that generate long - ranging tsunamis at other subduction zones have not been recorded in the trench.

The ocean plate is descending below North America at the Cascadia subduction zone, which runs from northern Vancouver Island, British Columbia, to Northern California.

Based on the very existence of ancient zircons, some geologists surmise that subduction occurred, at least intermittently, sometime around 4 billion years ago.

The findings could apply to other faults with similarly thick sediment, such as the Cascadia Subduction Zone in the Pacific Northwest, suggests study coauthor Andre Hüpers, a geophysicist at the University of Bremen in Germany.

A close study of the Haida Gwaii mainshock by Kao et al. revealed the Pacific plate slid at a low angle below the North American plate on a previously suspected thrust fault, confirming the presence of subduction activity in the area.

Oceanic plates form at ocean ridges and disappear into the Earth's mantle, a process known as subduction.

For example, the Caribbean coast of northern Colombia resembles a classic subduction zone with the potential for tsunamigenic M > 8 earthquakes at millennial time scales, but the absence of a large earthquake since 1492 is cause for complacency among local populations.

«At the time this thing formed, it was in the middle of a basin that was nowhere near a subduction zone — it was nowhere near the kind of geologic activity that would cause a volcano to form.»

The deep mantle - derived buoyancy, together with plate cooling at the surface, creates negative buoyancy that together explain the observations along the East Pacific Rise and surrounding Pacific subduction zones.

One of the primary questions they hope to answer is whether the pressures and temperatures experienced at depth here lead to the unusual properties of this subduction zone fault, and if that in turn leads to larger and more powerful earthquakes.

The seismic data collected by the Initiative has also helped Gao and her colleague Yang Shen at the University of Rhode Island, along with another study by Columbia University scientist Helen Janiszewski and Cornell University researcher Geoffrey Abers, to compile a picture of the CSZ structure that points to new places where the crushing pressure of subduction is squeezing water from and transforming rock at the trench where the Juan de Fuca plate is bending under the North American plate.

At certain subduction zones, such as those in Cascadia, Sumatra and eastern Alaska, a thick sediment layer overlies the subducting oceanic plate.

There was also a deeper slow slip event triggered on the subduction zone at 15 - 24 miles beneath the Kapiti Coast region, just west of New Zealand's capital city Wellington.

This finding has applications to the seismic hazard of these regions, as it highlights the potential for future damaging earthquakes and tsunamis at active subduction margins with no measurable recent uplift.

The findings, published in Nature Geoscience on Nov. 20, are important for understanding factors that influence earthquake and tsunami generation in Cascadia and at other subduction zones around the world.

A new study led by The University of Texas at Austin has found that the occurrence of these big, destructive quakes and associated devastating tsunamis may be linked to compact sediments along large portions of the subduction zone.

The triggering effect was probably accentuated by an offshore «sedimentary wedge» — a mass of sedimentary rock piled up at the edge of the subduction zone boundary offshore from the North Island's east coast.

«These kinds of long - streamer marine seismic studies provide the best tools available to the science community to efficiently probe subduction zones in high resolution,» said co-author Suzanne Carbotte, a research professor at Columbia University.

These three swarms seem to have prepared the subduction zone to rupture in the big 1 April quake, says Onno Oncken, a geophysicist at the German Research Centre for Geosciences in Potsdam.

The oceanic crust moves away from the mid-ocean-ridges and ultimately gets transported back into the underlying mantle through «subduction» at ocean trenches.

Intriguingly, the part of the subduction zone that broke was not the part that had built up the most stress, according to a ground - motion study of northern Chile's seismic gap by Marianne Métois, a geophysicist at the National Institute of Geophysics and Volcanology in Rome, and her colleagues (M. Métois et al.Geophys.

By studying the speed at which seismic waves travel in different directions through the same material, a phenomenon called seismic anisotropy, the researchers found that interior of the Nazca plate had been deformed during subduction.

Typically during subduction, plates slide down at a constant rate into the warmer, less - dense mantle at a fairly steep angle.

If the subduction zone near Sendai can produce a great quake, then other areas with similarly old ocean crust might too, says Okal, who says that Tonga and the northeastern Caribbean are regions to look at more closely.

The subduction zone along the western edge of South America, where the Nazca plate slides eastward beneath the South American plate at an average rate of about 6.5 centimeters per year, can indeed generate massive quakes.

«We are interested in large - scale geophysical processes, like how plate tectonics initiates and how plates move underneath one another in subduction zones,» said David Goldsby, an associate professor at the University of Pennsylvania.

The researchers also found that the fault zone was less than 5 metres thick, tens of times thinner than at other subduction zones, facilitating the slip (Science, doi.org/qdn).

«What this work shows is that, contrary to some previous estimates, the two middle sections of the Cascadia Subduction Zone that affect most of Oregon have a frequency that's more similar than different,» said Goldfinger, who directs the Active Tectonics and Seafloor Mapping Laboratory at OSU.

In high - pressure and high - temperature X-ray measurements that were partly conducted at DESY, scientists created conditions similar to those in so - called subduction zones where an oceanic plate dives under the continental crust.

Geological observations at Stardust Bay, Alaska point toward previously unrecognized tsunami sources along a presently creeping part of the Aleutian Subduction Zone.

«That tells us that most of this plume is primordial material and there are other materials hosted inside of this plume with low Helium - 3, -4, and these are likely crustal materials sent into the mantle at ancient subduction zones.»