Map and newspaper archives unravel eruptive histories of volcanoes

This 1891 map shows much of the saddle between Mauna Kea (at top of map) and Mauna Loa. Lava flows depicted as black irregular shapes in the lower half of the map were erupted from Mauna Loa, with labeled ages ranging from "ancient" to 1881. The Mauna Kea branch of the 1880-1881 lava flow, visible as a small, thumb-shaped flow at the bottom center of the map, sits atop the much larger 1855-1856 lava flow that also threatened Hilo. To see details of this extraordinary map, go to http://ags.hawaii.gov/survey/map-search/, enter "1718" in the "Registered Map No." box, and click "Search" to open the full resolution map. Map courtesy of Hawaii State Archives.