Taxonomy term

october 2014

Santiaguito Volcano's clockwork behavior provides an exceptional laboratory

If Earth breathes, Santiaguito Volcano in the Western Highlands of Guatemala could be its mouth. Roughly every half hour, like volcanic clockwork, Santiaguito’s active Caliente lava dome expands, filling with gas from depressurizing magma below. Then it exhales, often explosively, and deflates. Over the course of a day, you could almost keep time by it.

28 Sep 2014

Out of Africa, time and again

There is widespread agreement among scientists based on fossil and geochemical evidence that modern humans evolved in Africa between 200,000 and 100,000 years ago before spreading around the world. But the timing and route of this dispersal, and whether it occurred as a single exodus or in multiple pulses, remain contested. Now, a new study throws its weight behind a multiple-dispersal hypothesis, suggesting a first group of modern humans left Africa as early as 130,000 years ago, followed by a second about 80,000 years later.

27 Sep 2014

Boron proxies detail past ocean acidification

Pockmarked plankton shells and dead coral are becoming the hallmark images of ocean acidification. But this isn’t the first time seawater has dropped on the pH scale. Based on models of seawater chemistry, the ocean acidity during the Paleocene-Eocene Thermal Maximum (PETM), beginning about 56 million years ago, is the closest-known analog to today. Now, researchers using boron proxies preserved in microfossils to reconstruct surface-ocean chemistry suggest that acidification was more extensive and lasted longer than previously thought, although the PETM conditions still don’t outpace the current rate of ocean acidification.

25 Sep 2014

Climate impacting a few of our favorite foodstuffs

Researchers have found that the number of foggy winter days in California’s agriculture-heavy Central Valley has dropped 46 percent on average over the past three decades. Fog shields the valley from sunlight and contributes to the amount of “winter chill” — the amount of time spent between zero and 7 degrees Celsius during winter dormancy — that fruit and nut trees there experience. Sufficient winter chill is necessary for buds, flowers and fruit to develop properly, and although winter chill has previously been observed to have decreased since the 1950s, no one had conducted a long-term analysis of fog occurrence trends in the area, according to Dennis Baldocchi and Eric Waller of the University of California at Berkeley.

24 Sep 2014

Seeing beneath Greenland's ice

Save the handful of Vikings who settled an ice-free stretch of Greenland’s southwest coast during the Medieval Warm Period a millennia ago, few humans have ever laid eyes on even a fraction of the land that lies below Greenland’s 1.7-million-square-kilometer ice sheet. Now, courtesy of a new model, scientists are seeing a detailed view of the topography underlying the ice sheet, which is an important control on the flow and discharge of ice into the ocean.

23 Sep 2014

Of char and carbon: The story of a buried soil

The so-called Brady soil — a dark horizon up to a meter thick that underlies much of Kansas and Nebraska — is widespread but often unseen. The layer is a paleosol, or fossil soil, that formed about 15,500 to 13,500 years ago when the region was a stable grassland built atop dunes of thick, wind-blown loess. That changed when the Laurentide Ice Sheet retreated and dunes swallowed the grasslands.

22 Sep 2014

Virtual water: Tracking the unseen water in goods and resources

Trading in “virtual water” — rainfall and irrigation water used in the production of food commodities or other goods and services, but that isn’t part of the final product — between water-rich and water-poor regions has been suggested as a means to allay water scarcity. And recently, the virtual water concept has gained a foothold among a number of governments and multinational businesses, potentially shaping approaches to water sustainability in the future.

21 Sep 2014

Students send experiments to the International Space Station

As Orb-2, the latest mission to resupply the International Space Station (ISS), lifted off on July 13, no one at NASA’s Mid-Atlantic Regional Spaceport on Wallops Island, Va., was more thrilled than 16 elementary and high school students whose scientific experiments were on board the Cygnus spacecraft. The fifth through 12th graders represented 15 teams totaling 99 students from across the United States whose proposals had survived a rigorous screening program.

19 Sep 2014

Geologic Column: Combining art and geology in the sand

Once upon a time, sand sculptures made of sand were mostly castles, built by children and families on a summer vacation to the beach. Today, sand sculpting is also a serious business. But it all starts with the sand — which starts with geology.

18 Sep 2014

Comment: Building sanctuaries to increase civilization's resilience

Asteroid impacts, supervolcano eruptions, global pandemics, nuclear war and cyberterrorism: Each could cripple or destroy the foundations of civilization. Perhaps humanity should invest in its future by building archival sanctuaries to safeguard civilization in the event of catastrophe.

17 Sep 2014