Taxonomy term

subduction

Meteorite impacts may have kick-started ancient subduction

Earth in the Hadean Eon, between 4.56 billion and 4 billion years ago, was much too hot to support active plate tectonics as we know it today, where cold, established plates slowly march around Earth. Yet some evidence, including from tiny zircon crystals dating to the Hadean, has suggested that a form of plate tectonics was active by about 4.1 billion years ago — about a billion years before many researchers think modern plate tectonics started. The mechanisms that could have initiated and sustained early tectonics are unclear, but according to a new study, constant bombardment of early Earth by meteorites could have triggered temporary bursts of early tectonism.

22 Feb 2018

Limestone reservoirs boost volcanic carbon emissions

Volcanoes have been the main source of atmospheric carbon over Earth’s history, with some types of eruptions injecting more carbon into the atmosphere than others. Arc volcanoes, for example, which form in chains along subduction zones, are responsible for up to two-thirds of all volcanic carbon emissions today, and have likely been major contributors for as long as they’ve existed. New research suggests a reason why: These volcanoes draw large amounts of carbon from limestone platforms found along many subduction zones. The finding has implications for how the volcanic carbon cycle affects climate over geologic timescales.

18 Oct 2017

An absentee note for ancient blueschist: Lack of metamorphic rock does not date onset of plate tectonics

Plate tectonics is a defining characteristic of our 4.5-billion-year-old home planet, responsible for earthquakes, mountain building, and much of the evolution of the planet’s oceans and atmosphere. But when this formative process began is a mystery. Some researchers have pointed to the lack of blueschist — a type of metamorphic rock that only forms in tectonically driven subduction zones — in rocks older than 800 million years as a clue to when subduction began. But a new study rules this option out, offering a novel explanation for the rock’s absence in ancient rocks.

05 Apr 2016

How deep do the Alps go?

Continental crust was long thought to be too buoyant to subduct into the mantle, unlike denser oceanic crust, which descends into the mantle in many locations around the world. But the discovery of coesite — a type of silica formed at the extreme pressures present in subduction zones — in the Alps in 1984 challenged that long-held idea. Seismic evidence backing up claims that continental crust has indeed been subducted beneath the Alps has been scant, however, until now.
26 Jan 2016