On the horizon
As if California's recent earthquakes don't give seismologists enough to think about, now they might want to keep an eye on the nation's heartland.
Scientists at the University of Memphis find that strain is building rapidly in the New Madrid seismic zone, which takes in adjacent parts of Missouri, Arkansas, Tennessee, and Illinois. The rates of increase are comparable to those along California's San Andreas Fault.
Three great earthquakes struck the New Madrid region in 1811 and 1812. The ground shook as far away as the Great Lakes region and New England. The University of Memphis team, using fixed global positioning satellite receivers over four years, determined that strain is building rapidly in the New Madrid area. Their findings refute data published in 1999 that suggested the hazard was overstated. There is a 25 to 40 percent likelihood that a quake with a magnitude of six or more is likely within the next 50 years, says the US Geological Survey. A quake comparable to the 1811-12 events has a 7 to 10 percent probability. The results appear in Thursday's edition of Nature.
It may be pitch black at nearly 8,000 feet below the ocean's surface. But scientists have found a new organism there that ekes out its living through photosynthesis - turning light and nutrients into the energy it needs to survive. The discovery extends the domain of light-loving organisms to environments once deemed inhospitable to them. It also reinforces speculation about the range of environments suitable for life elsewhere in the solar system.
The green sulfur-loving bacteria, dubbed GSB1, relies on the faint glow emitted from deep-sea hydrothermal vents. The bacteria gathers the feeble light via receptors that scientists liken to tiny satellite dishes for their ability to pull in weak radiation. Researchers from the United States, Canada, and Bermuda discovered GSB1 during a research cruise over the East Pacific Rise, where magma wells up to form new material for the Earth's crust. Its findings are in the current issue of the Proceedings of the National Academies of Science.
Who gets bragging rights as the earliest glassmakers? To the artisans at Qantir-Piramesses in Egypt's eastern Nile Delta go the palm fronds - at least for now.
The other contenders come from Mesopotamia, according to a pair of British and German archaeologists, who report their findings in the current issue of Science. But earlier discoveries have been ambiguous. They come largely from workshops where glass products were made from "raw" glass, rather than from sites where bulk glass was produced. Such secondary workshops are evident in both areas and date roughly from 1,500 to 1,000 B.C.
Now comes evidence from Qantir-Piramesses of workshops where glass was made from its basic ingredients. The "smoking" furnace? A portion of a crucible that contains what the team describes as a heavily corroded block of raw glass. This and other evidence lead the team to infer that the ancient Egyptian artisans made semifinished glass by heating their materials at about 1,700 degrees F. Then they added coloring agents and produced finished ingots at nearly 2,000 degrees.
With global warming comes less salty water in the North Atlantic as rainfall increases and mountain glaciers melt. So say modeling results, bolstered by field measurements of past climate change.
Now hard numbers have been put to the 20th-century trend. Normally, an average 5,000 cubic kilometers of water - roughly the Amazon River's annual discharge - flows from the Arctic into the North Atlantic each year. But from 1965 to 1995, an extra 19,000 cubic kilometers of freshwater found its way south, say researchers from the Woods Hole Oceanographic Institution and the Norwegian Meteorological Institute. Half of that amount poured into the North Atlantic in the late 1960s, they say.
Freshening of North Atlantic waters is of concern because if the waters grow sufficiently less salty, the change is expected to slow a deep-sea "conveyor belt" that drives major currents worldwide and helps transfer heat from the tropics to the poles. The team concludes that at current freshening rates, a significant slowdown in the conveyor could occur in 100 years, with a shutdown coming in 200 years. The wild card, the team adds, is the rate at which Greenland's ice cap melts. The research appears in the current edition of the journal Science.