This map overlays a georegistered mosaic of thermal images collected during a helicopter overflight of the distal part of Kīlauea’s active East Rift Zone lava flow on February 19 at about 10:30 AM. The base image is a satellite image acquired in March 2014 (provided by Digital Globe). The perimeter of the flow at that time is outlined in yellow. Temperature in the thermal image is displayed as gray-scale values, with the brightest pixels indicating the hottest areas (white shows active breakouts).

The blue lines show steepest-descent paths calculated from a 1983 digital elevation model (DEM; for calculation details, see http://pubs.usgs.gov/of/2007/1264/). Steepest-descent path analysis is based on the assumption that the DEM perfectly represents the earth’s surface. DEMs, however, are not perfect, so the blue lines on this map can be used to infer only approximate flow paths.