Roiling pools of lava glow a deep orange, spewing fountains of lava and seemingly endless plumes of steam and gas. From space, the view is more subtle. The Advanced Land Imager (ALI) aboard the Earth Observing-1 (EO-1) satellite captured this natural-color image of activity within Ambrym’s caldera on December 13, 2012. Twin lava lakes on Ambrym’s Marum cone are visible. The larger of the two, which is gray, lies within Mbuelesu crater; to the southwest, Mbuelesu has a secondary crater that contains a pinkish-gray lava lake.
Active lava lakes often have a partly-solid, shiny gray crust that forms as the atmosphere cools their surfaces. The crust is rarely more than 5 to 30 centimeters (2 to 12 inches) thick and usually lasts just a few hours because it continually circulates, breaks, and sinks into the molten lava below. The pink color of the smaller lake suggests that surface was especially agitated and the crust was absent or in the process of sinking back into the lake.
Ambrym, one of the most active volcanoes in the world, is a large basaltic volcano with a caldera that is about 12 kilometers (7 miles) wide. Ambrym has existed for about 2,000 years; the most active vents—Marum and Benbow—have been roiling for the past 300 years. The Smithsonian's Global Volcanism Program maintains records of Ambrym’s activity and has a collection of numerous photographs taken by geologists who have done field work in the area.