Earth/Environment

Killer carbon burp
A big belch of carbon may be to blame for the mass extinction that swept the planet around 200 million years ago. A new study of wax from fossilized plants of the time suggests that 12 trillion tons of methane gas entered the atmosphere over just a few tens of thousands of years. Volcanic eruptions may have put enough heat-trapping carbon dioxide in the air to warm methane frozen in the seafloor and allow it to belch to the surface, a team led by Micha Ruhl of Utrecht University in the Netherlands writes in the July 22 Science. The extinction, which ended the Triassic period, shifted ecosystems in such a way that dinosaurs were able to dominate the planet. —Alexandra Witze

Ancient diamonds reveal crust’s moves
Diamonds from deep within the Earth suggest that the planet had begun its system of plate tectonics, in which great crustal plates shift across the surface, by 3 billion years ago. Scientists have long tried to fit together the puzzle of when and how plate tectonics began. Now, chemical analyses of tiny minerals trapped within the diamonds suggest that pieces of crust were getting mixed back deep into the planet’s innards by that time. Steven Shirey of the Carnegie Institution in Washington, D.C. and Stephen Richardson of the University of Cape Town in South Africa describe their work in the July 22 Science. —Alexandra Witze

Earth’s heat measured
About half the heat inside Earth is produced by radioactive elements. This estimate comes from the Kamioka Liquid Scintillator Antineutrino Detector, or KamLAND, a Japanese detector originally built to spot particles created in outer space but adapted to look downward for geoneutrinos released during the decay of uranium and thorium. While the relative abundances of these radioactive materials are still uncertain, the new heat estimate will be useful for computer simulations of the Earth’s interior, researchers report online July 17 in Nature Geoscience. —Devin Powell

Trees accelerate radon’s release
Australian researchers have identified a new means by which the radioactive gas radon can naturally escape from rocks in the soil. The water-soluble gas enters tree roots and then ascends into leaves, the team reports, from which it can be “exhaled.” In eucalyptus forests during midday, when tree exhalation rates peak, trees can boost radon releases by 37 percent over what soils emit directly, the scientists report online July 14 in Environmental Science & Technology. Since radon plays a role in the development of nanoscale particles that become cloud nuclei, this new process might help explain vegetation’s role in affecting climate. —Janet Raloff

BP blowout shows science of deep spills
Hydrocarbons spewed deep below the ocean behave quite differently from those released near the surface, new data show. Ordinarily, gases and volatile components of oil quickly vent into the air. But during the deep 2010 BP blowout, scientists sampled hydrocarbons as they were released at the seafloor. Light fractions preferentially dissolved into the water, leaving heavier and largely insoluble constituents to rise to the surface. These findings help explain the formation of deep-roving oil and gas plumes associated with this spill, scientists at the Woods Hole Oceanographic Institution in Massachusetts and colleagues report online July 18 in the Proceedings of the National Academy of Sciences. —Janet Raloff