Researchers say a massive cavity the size of two-thirds of Manhattan was found under a glacier in Antarctica. The pocket is a sign of "rapid decay" and just one of "several disturbing discoveries" made recently regarding the glacier, NASA's Jet Propulsion Laboratory said in a news release Wednesday. "[The size of] a cavity under a glacier plays an important role in melting," said Pietro Milillo of the Jet Propulsion Laboratory. "As more heat and water get under the glacier, it melts faster." The growing cavity sits in West Antarctica at the bottom of Thwaites Glacier, which is about as big...