Shaded-relief maps illustrate the changes that have occurred as a result of the current eruption in the crater of Mount St. Helens. At left, the steep, horseshoe-shaped crater rim, which formed during the catastrophic eruption of May 18, 1980, surrounds a circular, rough lava dome that grew between 1980 and 1986 as sticky, viscous lava erupted onto the crater floor. The smooth surface between the 1980-86 lava dome and the crater wall is a glacier that has been growing since 1986 – the youngest glacier in the United States. At right, the crater on December 11, 2004, three months after the start of the current eruption. Now, where there was once only ice, there is a new lava dome roughly one third the volume of the old one! And the eruption shows no sign of slowing down. Earthquakes have been continuing at a constant rate since mid-October 2004, and GPS measurements from equipment placed by helicopter onto the cooled portions of the lava dome have shown a continuous extrusion rate since that time. PHOTOS COURTESY HAWAII VOLCANOES NATIONAL PARK.

Pu`u `O`o cone on February 18 shows a clear view of the crater toward the southwest. Since 1987, repeated collapses of the cone have formed a crater more than 400 m (1,300 ft) long and about 250 m (820 ft) wide. The crater has been as deep as 210 m (690 ft), but lava flows erupted in the past few years have nearly filled the crater. PHOTO COURTESY HAWAII VOLCANOES NATIONAL PARK.

Radar specialist Mike Poland thought he was moving to a tropical paradise, but here he is back in the snow, preparing to measure tilt at the summit of Mauna Loa. PHOTO COURTESY HAWAII VOLCANO OBSERVATORY.