- News Home
12 December 2013 1:00 pm ,
Vol. 342 ,
Stefan Behnisch has won awards for designing science labs and other buildings that are smart, sustainable, and...
The iconic 125-year-old Lick Observatory on Mount Hamilton near San Jose, California, is facing the threat of closure...
Recent results from the Curiosity Mars rover have helped scientists formulate a plan for the next phase of its mission...
A new, remarkably powerful drug that cripples the hepatitis C virus (HCV) came to market last week, but it sells for $...
In pretoothbrush populations, gumlines would often be marred by a thick, visible crust of calcium phosphate, food...
Evolutionary biologists have long studied how the Mexican tetra, a drab fish that lives in rivers and creeks but has...
Victorian astronomers spent countless hours laboriously charting the positions of stars in the sky. Such sky mapping,...
In an ambitious project to study 1000 years of sickness and health, researchers are excavating the graveyard of the now...
- 12 December 2013 1:00 pm , Vol. 342 , #6164
- About Us
The Great Acid Lakes
30 April 1998 8:00 pm
Ancient lakes across a huge portion of the western United States may have been so acidic their waters would have dissolved a person's skin. The discovery, reported in the 30 April Nature, may force a reevaluation of some of Earth's old watering holes.
Scientists had assumed that a series of ancient lakes once scattered from Kansas to North Dakota were largely alkaline, because of the large quantities of salt found in the area's sandy reddish rocks that were formed when the lake evaporated about 270 million years ago. (Sea salt keeps today's oceans alkaline for instance.) But several years ago, Robert Goldstein, a geologist at the University of Kansas in Lawrence, and Robert Burrus of the U.S. Geological Survey happened to test salt from one of these rocks with a laser spectrometer and found that it contained something surprisingly acidic.
Kathleen Benison, then Goldstein's graduate student, has now evaluated these rocks in detail. The acidity, she says, comes from tiny drops trapped in the salt deposits, which were left behind when the lakes evaporated. The drops contained large amounts of dissolved sulphate and acidic sulpher complex HSO4-. Benison, now at Central Michigan University in Mt. Pleasant, estimates that the lakes and groundwater in this part of the Midwest must have been highly acidic, with a pH between 0 and 1. Her analysis assumes the preserved droplets are identical to the ancient lake water.
How such vast bodies of highly acidic water could have formed is a mystery. Although small quantities of acid often develop naturally, large pools of highly acidic water are rare because there are usually some rocks or minerals containing carbonate to neutralize the acid. "As far as we know, this is the most acidic lake and groundwater system ever found outside of a volcanic area," she says, adding that there's no evidence of ancient volcanism in the U.S. Midwest.
"These are interesting and unexpected results," says sedimentologist Russell Dubiel of the U.S. Geological Survey in Denver, Colorado, it "goes against what the classical interpretations are, and ought to be followed up."