Volume 10 Issue 1, January 2017

Organic carbon decomposition in anoxic marine sediments was thought to be dominated by bacteria, but experimental data and microbial culture studies now show that microalgae buried in coastal sands may also play an important role in carbon turnover.

180 million years ago Earth's continents were amalgamated into one supercontinent called Pangaea. Analysis of oceanic crust formed since that time suggests that the cooling rate of Earth was enhanced in the wake of Pangaea's dispersal.

Abrupt climate changes in the glacial North Atlantic altered the position of wind systems in the Northern Hemisphere and tropics. Ice-core data show that this disruption also reached the southern westerlies.

The MESSENGER spacecraft has revealed geochemical diversity across Mercury’s surface. Magma crystallization experiments suggest a crustal mineralogy consistent with a transition towards shallower and cooler mantle melting conditions.

The Moon is thought to have initially had a magma ocean that gradually solidified. Crystallization experiments find that the resulting crustal thickness depends on water content and is consistent with significant water in the early Moon.

Ocean acidification can affect growth and calcification rates of calcifying phytoplankton. Mesocosm experiments reveal that acidification can also cause declines in population size and inhibit bloom formation.

Nitrogen losses have not been observed in the Bay of Bengal, unlike in other ocean oxygen minimum zones. Chemical and molecular analyses reveal that trace levels of oxygen inhibit nitrate formation, largely preventing microbial N₂ production.

Bacteria have been assumed to dominate organic matter decomposition in marine sediments. In flow-through reactor experiments, algae were revealed to be primarily responsible for anaerobically metabolizing organic matter in permeable sediments.

Abrupt glacial climate changes were slowly communicated between hemispheres by oceanic heat transport. Ice core data point to more rapid atmospheric teleconnections linking the North Atlantic, tropics, and southern storm track.

The composition of the oceans on early Earth has been challenging to assess. Calcium isotope records from carbonate rocks formed 1.9 to 2.7 billion years ago rule out high alkalinity, and are consistent with moderate to high CO₂ concentrations.

Rocks are altered by high pressure during subduction. Analysis of exhumed metamorphic rocks suggests that the peak pressures recorded within minerals mark a change in tectonic regime within a subduction zone, rather than burial depth.

The controls on fast versus slow fault slip in subduction zones are unclear. Rock deformation experiments suggest that faults within the seismogenic region of a subduction zone may slip aseismically due to pressure solution creep.

Thicker oceanic crust forms from a hot mantle. Observations of unusually thick oceanic crust that formed 170 million years ago in the Atlantic and Indian oceans suggest that the ancient supercontinent Pangaea helped insulate and warm the mantle.

Satellite observations have detected localized magnetic field changes at high latitudes. Simulations suggest these changes can be explained by a westward jet in the liquid core, which has been accelerating over the past 15 years.