Deep-sea action.

Scientists using remotely operated vehicles have reported the first close-up observations of a deep undersea volcano during its eruption.

The peak lies about 60 kilometers northwest of Rota, one of the Western Pacific's Northern Mariana Islands. The base of the volcano, called NW Rota-1, is about 16 km across and lies beneath 2.7 km of water, says Robert W. Embley, a marine geologist at the National Oceanic and Atmospheric Administration in Newport, Ore. The summit, however, rises to within 520 meters of the ocean surface.

Embley and his colleagues in 2004 discovered the summit in full eruption, spewing a yellow plume from a 15-m-wide crater on the volcano's southern flank--a feature the scientists dubbed Brimstone Pit. Samples from the plume included volcanic ash and droplets of molten sulfur, the team reports in the May 25 Nature.

On several occasions, scientists have studied underwater volcanoes as they've grown to the ocean surface. However, researchers have previously observed evidence of deep-sea eruptions only after they've ceased, says Embley.

A visit to NW Rota-1 in October 2005 again found the eruption in full swing. Two months ago, yet another trip to the undersea peak noted red-hot lava of at least 1,000[degrees]C inside Brimstone Pit.--S.P.