Thunder Down Under: Tweed Volcano, Australia

Australia, the only continent with no current volcanic activity, is home to one of the world's largest extinct volcanoes: Tweed Volcano, shown in this 3-D stereo image pair. Eruptions here ended about 20 million years ago. Twenty million years of erosion have left this landform deeply eroded yet very recognizable as a caldera with a central peak--the erosional stub of the central pipe that carried magma upward to Earth's surface.
Credit: NASA/JPL/NGA