Lake Mead’s falling water level has exposed several shocking things in recent months – previously sunken boats, old war ships and human remains.The record-low water levels are exposing sedimentary rocks that haven’t been seen since the 1930s when the Hoover Dam was built and Lake Mead filled.“We knew that these ash units existed, but we were surprised to find so many as the Lake Mead water level lowered,” said Eugene Smith, an emeritus professor of geology at UNLV and co-author of the study.Scientists are taking advantage of the low levels to study sediment that hasn’t been exposed in nearly a century.The latest discovery in Lake Mead may be one of the “better” collections of volcanic ash from that period of time, Lowenstern said, and it will “be important in allowing us to reconstruct the geologic history of the region, and to understand the frequency of large volcanic eruptions and their impact on the Southwest.”Ash from even moderately explosive volcanic eruptions can travel hundreds of miles, blanketing areas as far away as several meters with heavy material."