Posts Tagged ‘earth’s’

We’ve created a ‘bubble’ around the Earth

The effects of human activity have long been cited as a primary cause of global climate change, but new research from NASA has revealed that our use of technology also appears to be having an impact not just on the planet, but on Earth’s near-space environment as well. As the US space agency announced on […]

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Atmosphere discovered around ‘super Earth’ for the first time ever

In what is being hailed as “a significant step on the path towards the detection of life outside our Solar System,” astronomers have detected an atmosphere around the exoplanet GJ 1132b, which makes it the most Earth-like world around which such a layer of gasses has ever been found. According to Space.com, GJ 1132b is […]

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Implications for metal and volatile cycles from the pH of subduction zone fluids

The chemistry of aqueous fluids controls the transport and exchange—the cycles—of metals and volatile elements on Earth. Subduction zones, where oceanic plates sink into the Earth’s interior, are the most important geodynamic setting for this fluid-mediated chemical exchange. Characterizing the ionic speciation and pH of fluids equilibrated with rocks at subduction zone conditions has long been a major challenge in Earth science. Here we report thermodynamic predictions of fluid–rock equilibria that tie together models of the thermal structure, mineralogy and fluid speciation of subduction zones. We find that the pH of fluids in subducted crustal lithologies is confined to a mildly alkaline range, modulated by rock volatile and chlorine contents. Cold subduction typical of the Phanerozoic eon favours the preservation of oxidized carbon in subducting slabs. In contrast, the pH of mantle wedge fluids is very sensitive to minor variations in rock composition. These variations may be caused by intramantle differentiation, or by infiltration of fluids enriched in alkali components extracted from the subducted crust. The sensitivity of pH to soluble elements in low abundance in the host rocks, such as carbon, alkali metals and halogens, illustrates a feedback between the chemistry of the Earth’s atmosphere–ocean system and the speciation of subduction zone fluids via the composition of the seawater-altered oceanic lithosphere. Our findings provide a perspective on the controlling reactions that have coupled metal and volatile cycles in subduction zones for more than 3 billion years7.

Radical overhaul needed to halt Earth’s sixth great extinction event

By Bill Laurance, James Cook University and Paul Ehrlich, Stanford University Life has existed on Earth for roughly 3.7 billion years. During that time we know of five mass extinction events — dramatic episodes when many, if not most, life forms vani…

NASA: ‘New study shows Mercury is shrinking’

A new NASA-funded study appearing in the October edition of the journal Nature Geoscience has found previously undiscovered cliff-like landforms on Mercury – a discovery which appears to indicate that the planet, like Earth, is currently a tectonically active world. Using images obtained by the Mercury Surface, Space Environment, Geochemistry and Ranging spacecraft (MESSENGER), Tom […]

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