Earth Observations taken by the Expedition 18 Crew

ISS018-E-005321 (24 Oct. 2008) --- The Hell's Half Acre Lava Field in Idaho is featured in this image photographed by an Expedition 18 crewmember on the International Space Station. Located in eastern Idaho, the Hell's Half Acre Lava Field is the easternmost large field associated with the Snake River Plain that arcs across the center of the state. The abundant lava flows and other volcanic rocks of the Snake River Plain are thought to be the result of southwest passage of the North American tectonic plate over a fixed mantle plume or "hotspot". According to scientists, Volcanism attributed to the hotspot began approximately 15 million years ago in the western portion of the Plain, with lava fields becoming younger to the east -- with lavas erupted approximately 4,100 years ago, Hell's Half Acre is one of the youngest lava fields. Today, the center of hotspot volcanism is located in Yellowstone National Park and feeds the extensive geyser system there. Portions of the Hell's Half Acre Lava Field are designated as a National Natural Landmark and Wilderness Study Area. This detailed photograph illustrates the forbidding landscape of the basaltic lava field -- the complex ridge patterns of the black to grey-green flow surfaces, comprised of ropy pahoehoe and blocky A a lava, are clearly visible. Regions of tan soil surrounded by lava are known as kipukas -- these "islands" are windows onto the older underlaying soil surface as they were never covered by lava. The kipukas are used for agriculture (both crops and grazing) -- several green fields are visible to the northwest of Interstate Highway 15 (right). Light to dark mottling visible in the kipukas is most likely due to variations in moisture and disturbance by agricultural activities.