More than 31 years after Mauna Loa last erupted, sending lava within 4.5 miles of Hilo, the largest active volcano in the world is showing signs of unrest. Scientists at the U.S. Geological Survey Hawaiian Volcano Observatory Thursday elevated the Volcano Alert Level for Mauna Loa from "normal" to "advisory." There are four levels of alerts: "normal" — or background level, "advisory," "watch," and "warning" to inform the public about a volcano's status. The change in status indicates the volcano is showing signs of unrest that are above known background levels, but it does not mean an eruption is imminent or certain, officials said. Normally, Mauna Loa sees up to 10 earthquakes per week, and recently that has escalated to 40 earthquakes per week. Prior to eruptions in 1975 and 1984, about 100 earthquakes were recorded each day. "We expect the seismicity to grow steadily and be more consistent and persistent, and even the rates to change before we forecast an eruption," predicted Frank