Weird Brown Foam Covers Lake Mead

Tests are being run on a mysterious brown foamy substance found covering a large part of America's biggest reservoir. Initial tests on the substance—found in the Overton Arm area of Lake Mead along with dozens of dead carp—have revealed nothing toxic but investigators have returned for more samples, the Las Vegas Sun reports. A spokesman for the Southern Nevada Water Authority says no problems have been detected at intakes yet, stressing that the lake is so big that water from the affected area takes around a month to make its way to the intake area. (More Lake Mead stories.)