RESEARCH HIGHLIGHTS

high pressures in the past. This, as well Dusty forests Glacial Florida fl ow as elevated concentrations of nickel, chromium and iridium in the layer Paleoceanography 23, PA1217 (2008) relative to the surrounding rocks, The Florida Current is part of the is strongly suggestive of a meteorite return flow of the Atlantic meridional impact. The layer was probably caused overturning circulation, carrying by a meteorite impact into wet sediments South Atlantic waters at intermediate that resulted in the fragmentation of depth towards the North Atlantic rocks and vaporization of water in Ocean. A new study suggests that the sediments. this flow broke down during the last This feature might serve as an glacial termination. analogue for similar deposits on Mars that Rosemarie Came at Woods Hole are thought to have resulted from impacts Oceanographic Institution, Massachusetts, into fluid-rich rocks. USA, and colleagues used benthic foraminifera to reconstruct the nutrient content in the intermediate waters of the Volcanoes in chaos Florida Current during the last glacial SE’MHUR termination. The team found a dramatic decrease in nutrient content for over Global Biogeochem. Cycles 22, GB1027 (2008) 1,000 years from the beginning of the Tropical montane rainforests are among the Younger Dryas cold reversal, reflecting most species-rich ecosystems in the world. increased influence of northern-source Oft en found in nutrient-poor soils, we know water at the sites. little about how these forests derive their These changes are associated with nutrition. A recent study suggests that Andean a decrease in meridional overturning montane rainforests obtain a considerable circulation and North Atlantic part of their nourishment from Saharan dust. Deep Water production during the Jens Boy and Wolfgang Wilcke of Younger Dryas event. the Johannes Gutenberg University Mainz, Germany, compared atmospheric nutrient inputs into these ecosystems Scottish impact with temporal changes in dust transport from the Sahara over a five-year period. Geology 36, 303–306 (2008) UNIVERSITY NASA/JPL/ARIZONA STATE They found that nutrient-rich Saharan A new study suggests that a rock layer in dust is being deposited in, and taken up Scotland that was previously interpreted to Icarus 194, 487–500 (2008) by, Andean forests. The extent of this be volcanic in origin was instead formed Deep, extensive depressions on the deposition is increased during the La Niña during an ancient meteorite impact. surface of Mars, called chaotic terrains, phase of the El Niño–Southern Oscillation. Kenneth Amor from the University of are generally believed to have formed If the frequency of El Niño–Southern Oxford, UK and his colleagues undertook when magma intruded into frozen ground Oscillation events increases as a result of a detailed investigation of this rock layer, or water-bearing rocks, causing a collapse. global warming, it could lead to changes which formed over a billion years ago A recent study reports the presence of in dust deposition and consequently in what is now northwestern Scotland. numerous small volcanoes within one the nutrient budgets of the Andean The structure of minerals within this such chaotic terrain and provides direct tropical forests. layer indicates that they experienced evidence for magmatic activity. Sandrine Meresse from the IDES, Université Paris-Sud, France and her colleagues studied various types Ephemeral oasis of spacecraft-derived images of the Hydraotes Chaos terrain on Mars. Geosphere 4, 375–386 (2008) these lakes. Beginning in August 2003, They identified and documented In 1998, Lake Nasser — the immense water stopped flowing in from Lake the morphological traits of several artificial reservoir created by the Aswan Nasser; however, evaporation of the lake scattered conical features with pits High Dam — overflowed its banks, water continued. As a result, the lakes on their summits. Although they do leading to the formation of five new have been continuously shrinking. If the resemble some non-volcanic features lakes in the Sahara Desert region of rate of evaporation remains the same, the as well, the overall morphology of the western Egypt. A new study suggests lakes will cease to exist by March 2011. cones is very similar to volcanic cones that these lakes, which at one point Moreover, the underlying Nubian aquifer on Earth, suggesting a volcanic origin of covered over 1,500 square kilometres, was not replenished because the lakes these features. may soon be just a salty memory. formed over impermeable rock. The relationship of the cones to Mohamed Abdelsalam of the Missouri The extensive layer of salt that other features in the Hydraotes Chaos University of Science and Technology, might be left behind does not bode well terrain indicates that the cones formed USA and colleagues used satellite images for plans for increased agriculture in late in the developmental history of to track the formation and evolution of this area. these terrains, after most of the collapse had occurred. nature geoscience | VOL 1 | MAY 2008 | www.nature.com/naturegeoscience 287 © 2008 Nature Publishing Group