A volcanic eruption at a national park triggered an explosive rock storm and ash plume, forcing emergency evacuations of visitors and nearby communities. Scientists warn of continued seismic activity. A national park was abruptly evacuated Wednesday after a volcanic eruption sent an explosive rock storm and ash plume thousands of feet into the air, catching visitors and park officials off guard. The eruption, which began mid-morning local time, hurled volcanic bombs some the size of cars across the landscape and blanketed surrounding areas in fine gray ash. Park rangers scrambled to evacuate hundreds of visitors as pyroclastic flows cascaded down the volcano's slopes. Video captured by fleeing tourists showed dark ash clouds billowing behind them as they raced toward exits. "It sounded like a continuous thunder, and then the sky went black," said one evacuee. "We could feel rocks hitting the ground around us." The eruption triggered a "rock storm" phenomenon, where ejected volcanic material rains down over a wide area, damaging vehicles, structures, and vegetation. Authorities closed all roads leading into the park and established an exclusion zone extending several miles from t...