An undersea volcano about 300 miles (480 km) off Oregon's coast has been spewing lava for the past seven days, confirming forecasts made last fall and giving researchers unique insight into a hidden ocean hot spot, a scientist said on Friday.

Researchers know of two previous eruptions by the volcano, dubbed "Axial Seamount" for its location along the axis of an underwater mountain ridge, Oregon State University geologist Bill Chadwick said. But those 1998 and 2011 eruptions were detected months or years afterward, Chadwick added.

Last year, researchers connected monitoring gear to an undersea cable that, for the first time, allowed them to gather live data on the volcano, whose peak is about 4,900 feet (1,500 meters) below the ocean surface.