Volume 7 Issue 1, January 2014

The deaths of 11 rescue workers that set out to help a research boat in stormy Arctic waters highlights the perils of collecting data at sea.

Large quantities of methane lie trapped beneath the floor of the Arctic Ocean. Measurements in the southern Laptev Sea around the Lena River delta suggest that bubbles and storms facilitate the flux of some of this submarine methane to the atmosphere.

The Archaean Earth was much hotter than today. Numerical modelling shows that the base of thickened crust that formed at the time would have been so dense that it dripped back into the mantle.

Liquid water may lurk beneath the frozen surfaces of Jupiter's moon Europa and other icy worlds. Extending ocean science beyond Earth, planetary oceanographers are linking Europa's ocean dynamics to its enigmatic surface geology.

The metal content of magmas erupted at subduction zone arcs is thought to be derived from the mantle. A correlation between crustal thickness and copper content in arc magmas worldwide, however, reveals an important role for the crust in the upper plate.

In many planetary atmospheres, including that of Earth, the base of the stratosphere—the tropopause—occurs at an atmospheric pressure of 0.1 bar. A physically based model demonstrates that the pressure-dependence of transparency to infrared radiation leads to a common tropopause pressure that is probably applicable to many planetary bodies with thick atmospheres.

On Jupiter’s icy moon Europa, enigmatic chaos terrain—where the icy crust is cut by a jumble of ridges and cracks—occurs most commonly at lower latitudes. Simulations of convection in the ocean underlying Europa’s icy crust suggest that ocean dynamics can control an enhanced flow of heat to Europa’s equatorial surface, and hence geological activity.

The first known phosphorus-rich deposits formed 2 billion years ago, but their origins are unclear. Geochemical and palaeontological analyses of 2-billion-year-old deposits from northwest Russia suggest that the presence of sulphur-oxidizing bacteria and a sharp oxic–anoxic transition in the sediments allowed for phosphorus accumulation in this setting.

The Archaean rocks of Isua, West Greenland, contain graphite, but its origins are debated. Geochemical and microscopic analyses suggest that the graphite was formed from biologically formed carbon that was deposited at least 3.7 billion years ago.

At mid-ocean ridges, the movements between rift segments are usually accommodated by transform faults that are oriented perpendicular to the rift axis. Analysis of seismic data from rift segments exposed in Iceland shows that such movements can also occur through the rotation of several small faults and crustal blocks that slip like books tilting on a shelf.

The Canterbury earthquake sequence that struck New Zealand in 2010 and 2011 was characterized by an extended series of aftershocks. Analysis of seismic data show that a broad region of previously strong crustal rocks was weakened during the mainshock, and variations in crustal strength may have contributed to the protracted seismic activity.

Great earthquakes in the Himalaya are thought to occur mostly along the range front. Field mapping and radiocarbon dating reveal earthquake rupture on a previously unrecognized fault in the interior of the western Himalaya, which forms part of a key structural component of the mountain range, implying that seismic risk evaluations should be revised.

The characteristics of magmas typically associated with porphyry copper deposits are thought to be imparted in the mantle. Statistical assessment of over 40,000 geochemical analyses of magmatic rocks formed in subduction zones worldwide, however, shows that the characteristics of these magmatic rocks are systematically controlled by the thickness of the arc crust.

The volume of Archaean crust preserved at Earth’s surface today is low. Thermodynamic calculations and geodynamic modelling show that the thick, primary crust that would have formed on a much hotter Archaean Earth was denser than the underlying mantle, and would have therefore been recycled back into the mantle as drips.

Dark streaks that appear on the surface of Mars during warm seasons have been observed at the mid-latitudes and tentatively attributed to the flow of briny water. Imagery from the Mars Reconnaissance Orbiter over multiple Mars years suggests that these seasonally active features are also present in equatorial regions, where liquid surface water is not expected.

Ancient valleys suggest a warm early Mars where liquid water flowed, but a greenhouse effect strong enough to offset a dim early Sun has been difficult to explain. Climate simulations suggest that sufficient concentrations of the greenhouse gases CO₂ and H₂ — outgassed during volcanic eruptions — could have warmed Mars above water’s freezing point.

Vast quantities of carbon are stored in shallow Arctic reservoirs, such as subsea and terrestrial permafrost. Observations in the Laptev Sea suggest that bubbles deliver significant quantities of the methane stored in subsea permafrost to the overlying water column.

Volcanic eruptions are often preceded by long-period seismic events that were thought to be generated by the resonance of cracks filled with magmatic fluid. Analysis and modelling of long-period seismicity at volcanoes in Italy, Costa Rica and Peru shows that it could instead be caused by slow rupture along faults in the upper volcanic edifice.