Published by the American Geological Institute
Newsmagazine of the Earth Sciences
Drought in northern Africa could be killing corals in the Caribbean,
says Eugene Shinn of the U.S. Geological Survey. He compared the history
of Caribbean reefs with Barbados dust records from the Cooperative Institute
for Marine and Atmospheric Studies at the University of Miami and found
periods of high dust levels over the last 25 years that coincided with
the emergence of diseases that have decimated the Caribbean coral reef.
Shinn and colleagues collected air samples over the Virgin Islands that
carried 88 different species of bacteria and 22 species of fungi, including
Aspergillus sydowii — the soil fungus destroying sea fans in the Caribbean
coral reefs. On Dec. 12, SeaWiFS instruments captured this image of a dust
storm moving west from Africa. The dust may also be linked to asthma, the
decrease of oxygen in estuaries and red tide, Shinn says.
Racing for the surface
Researchers have found that granitic magma has a lower viscosity and can travel up through the mantle much faster than was previously believed. Alexander Cruden of the University of Toronto and his international team of scientists published findings in the Dec. 7 Nature indicating that the generation, segregation, ascent and emplacement of a granite pluton can take place over a geologically miniscule amount of time. Granite comprises 70 to 80 percent of the continental landmass and scientists have long believed that its emplacement occurs over many millions of years as the buoyant, silica-rich plutons slowly rise toward the upper crust. Cruden and his colleagues conducted field work and used physical and theoretical models to reconstruct the formation of massive intrusions as well as small dykes. They found that no matter what the size of the granite intrusion, the more fluidic and less crystallized nature of the magma meant the amount of time that it took to reach the upper crust was on the order of thousands, rather than millions, of years.
Is talc bad for baby?
Mothers might want to reconsider buying baby powder and some feminine hygiene products because cosmetic talc, or common baby powder, has been nominated for inclusion on the National Institute of Environmental Health Sciences (NIEHS) list of carcinogenic substances. Scientists have known that the tiny, spear-like crystals that painlessly pierce the lungs of talc miners can cause some forms of lung cancer. As a result, NIEHS and the National Toxicology Program have listed asbestiform talc as a carcinogenic substance. In 1987, the International Agency for Research on Cancer concurred with the NIEHS. At that time, non-asbestiform talc — one of its most common household forms is baby powder — was not considered carcinogenic. Since then several studies have shown a possible link between non-asbestiform talc and the occurrence of cancer in humans, particularly some forms of ovarian cancer in women who use feminine hygiene products that contain talc.
Sedimentary, my dear Mars
Crisp and clear pictures of sedimentary rock layers on Mars are providing the strongest evidence yet of the planet’s watery past. Physicist Michael Malin of Malin Space Science Systems, whose camera aboard the Mars Global Surveyor shot the high-resolution photos, announced the discovery with colleagues on Dec. 4 and reported their find in the Dec. 7 Science. The layers may have developed as dust settled out of the atmosphere, but the regular thickness of some, is similar to deposition of sedimentary rocks on Earth formed in bodies of water. On Mars, the layers indicate crater lakes and shallow seas may have dotted the landscape 4 billion years ago.