Articles in 2012

The mid-ocean ridges mark the lines along which the Earth is turning itself inside out through the process of plate tectonics. Advances in technology are helping to reveal the intricate details of the magma systems that feed the rifting process.

Earth's crust is formed where tectonic plates rift apart and upwelling magma solidifies. Disparate observations from rifts beneath the oceans and on land provide insights into the dynamics of rifting and opportunities for synthesis.

The supply of magma to Kīlauea Volcano was relatively stable for 50 years. But between 2003 and 2007, the volcano experienced a surge in the supply of magma from the mantle that implies short-term changes in the underlying Hawaiian hotspot.

Most of Earth's crust is created at mid-ocean ridges that are submerged deep beneath the oceans. Analyses of geodetic and seismic data from rare sections of ridges that are exposed on land in Iceland and the Afar region in east Africa demonstrate that rifting episodes at these sites operate with remarkably similar mechanisms.

The plausibility of the high end of global warming projections in recent assessments is a subject of debate. A study of multi-model climate simulations argues that we need to take the possibility of strong warming seriously.

A giant impact on the young proto-Earth is thought to explain the formation of the Moon. High-precision analysis of titanium isotopes in lunar rocks suggests that the Moon and Earth's mantle are more similar than existing models permit.

Geochemical evidence continues to challenge giant impact models, which predict that the Moon formed from both proto-Earth and impactor material. Analyses of lunar samples reveal isotopic homogeneity in titanium, a highly refractory element, suggesting lunar material was derived predominantly from the mantle of the proto-Earth.

The supply of magma to Kīlauea Volcano, Hawai‘i, was thought to have been steady over the past decades. Measurements of deformation, gas emissions, seismicity and lava composition and temperatures show that instead magma supply from the mantle doubled in 2003–2007, implying that hotspots can provide varying amounts of magma over just a few years.

The global-mean temperature evolution over the course of the twenty-first century is uncertain. Simulations with an ensemble of thousands of climate models that reproduce observed warming over the past 50 years suggest that a mid-range greenhouse-gas emissions scenario without mitigation could lead to a warming of between 1.4 and 3 K by 2050, relative to 1961–1990.

Rifting of the eastern part of the East African Rift System was thought to have begun several million years before its western counterpart. Reconstructions of drainage development, combined with dating of rift-related volcanic activity, suggest that rifting in the western branch may instead have begun at the same time as in the eastern branch.

Before the rise of oxygen, the atmosphere of the early Earth may have consisted of an organic haze. Geochemical data and modelling suggest that from 2.65 to 2.5 Gyr ago, several transitions between hazy and haze-free atmospheric conditions occurred, potentially linked to variations in biogenic methane production.

Latitudinal variations in the location of the southern westerly wind belt have been associated with millennial-scale climate variations during the last glacial period. A reconstruction of sea-surface temperatures off the southern coast of Australia suggests that these climate variations also drove changes in the location of the oceanic subtropical front.

The atmospheric nitrous oxide concentration has increased by 20% since 1750. Analyses of Antarctic firn and archived air samples reveal seasonal cycles in the isotopic signature of nitrous oxide, which can help to disentangle the contribution of surface sources.

Thermal models predict that spreading velocity at mid-ocean rifts should influence the geometry of the underlying magma chamber. InSAR data from the slow-spreading Ethiopian Rift identify a shallow, elongated magma chamber—a feature usually associated with fast-spreading rifts—beneath the Erta Ale segment, implying that spreading velocity may not be so important after all.

Iron is often a limiting nutrient in ocean regions that have a constant supply of other macro-nutrients, and changes in iron supply over time have been linked to fluctuations in primary productivity. Marine sediments from the equatorial Pacific Ocean show that over the past million years, iron input was linked to the export and burial of biogenic silica.