Volume 5 Issue 7, July 2012

Mountain roads and trails are proliferating throughout developing southeast Asia. The long-term consequences of associated landslides and surface erosion on downstream aquatic environments could be severe, but are largely unrecognized.

Lichens, cyanobacteria, mosses and algae coat many terrestrial surfaces. These biological covers turn out to play an important role in the global cycling of carbon and nitrogen.

Most volcanism on Earth takes place under water, yet little is known about submarine eruptions. Monitoring of two volcanic seamounts beneath the Pacific Ocean reveals the pulsed nature of their eruption cycles.

Despite variable forcing by tectonics, the height of mountain ranges seems to be limited. Satellite imagery suggests that landsliding rates adjust to large changes in uplift, acting to maintain hillslopes of similar steepness.

Mercury concentrations in the Arctic atmosphere exhibit a pronounced peak during summer. Model simulations suggest that this can be explained only if boreal rivers deliver large quantities of mercury to the Arctic Ocean.

Aerosol concentrations in China have reached unhealthy levels, at least locally. Model simulations suggest that a significant contribution comes from the weakening monsoon circulation in past decades, trapping more pollutants over land.

The last deglaciation was punctuated by several millennial-scale climate changes. In the Gulf of California, the cold stages were marked by decreased upwelling, opposite to the changes expected if these shifts were analogous to modern seasonal variability.

The growth of the smallest atmospheric particles to sizes at which they may act as seeds for cloud droplets is a key step linking aerosols to clouds and climate. A synthesis of research indicates that the mechanisms controlling this growth depend on the size of the growing particle.

Many terrestrial surfaces are covered by photoautotrophic communities, which are capable of synthesizing their own food from inorganic substances using sunlight. According to an analysis of previously published data, these communities account for nearly half of the biological nitrogen fixation on land.

Star dunes are common in sand seas, but the mechanisms driving their formation are unclear. Numerical modelling indicates that the morphology of the dunes is controlled by the frequency of changes in the wind regime.

The steep topography of mountain landscapes arises from interactions between tectonic rock uplift, valley incision and landslide erosion on hillslopes. An analysis of more than 15,000 landslides in the eastern Himalaya, mapped from satellite images, shows that steep uplands primarily respond to uplift and river incision by increases in landslide erosion rates rather than by steepened hillslope angles.

The Axial Seamount submarine volcano exhibits an inflation–deflation cycle comparable to similar volcanoes on land. Measurements of ocean bottom pressure document the entire inflation–deflation cycle between eruptions at Axial Seamount in 1998 and 2011, and imply that the timing of submarine eruptions could be more predictable than that of their subaerial counterparts.

For volcanoes at submarine rift zones, a direct link between seismicity, seafloor deformation and magma intrusion has not been demonstrated. Recordings from ocean-bottom hydrophones and bottom-pressure recorders map an increasing rate of seismicity at Axial Seamount, northeast Pacific, over several years before its eruption in April 2011.

At frequently active submarine volcanoes, it is difficult to distinguish between new and pre-existing lava flows. A combination of high-resolution bathymetric surveys taken before and after an eruption at Axial Seamount in 2011 allows detailed mapping of the 2011 lava flows, and highlights the tendency of new flows to mimic older ones.

During subduction, the seawater-altered lithosphere becomes dehydrated and expels fluids. Isotopic analysis of an exhumed oceanic slab in the Tianshan Mountain Range shows that although subduction can continue for many millions of years, fluids are expelled in short-lived channels over periods of just a few hundred years.

The structure of the European crust and upper mantle is precisely known only in limited regions. A new tomographic model for the entire European upper mantle identifies northeastward subduction of the Adria plate beneath the Dinarides Mountains, volcanism related to the upwelling Eifel hotspot and mantle delamination beneath Scandinavia.

Human activities, including industry and mining, have increased inorganic mercury deposition in terrestrial and aquatic ecosystems. Model simulations indicate that circumpolar rivers deliver large quantities of mercury to the Arctic Ocean during summer.

Seagrass meadows are some of the most productive ecosystems on Earth. An analysis of organic carbon data from just under one thousand seagrass meadows indicates that, globally, these systems could store between 4.2 and 8.4 Pg carbon.

The vast majority of Earth’s volcanoes are under water, but little is known of the structure and evolution of submarine volcanoes. A bathymetric survey mapping the Monowai submarine volcano in the Tonga–Kermadec Arc twice within 14 days reveals dramatic changes in bathymetry of up to 71.9 m, associated with volcanic activity.

Most volcanism on Earth occurs beneath the oceans, but submarine volcanoes are difficult to study. Advances in seafloor monitoring have opened up an unprecedented view of eruptions on the seabed. In this web focus we present opinion pieces and research articles that document the cycle of inflation and deflation, lava flows, and growth and collapse of two volcanoes beneath the Pacific Ocean during eruptions in 2011.