In a 2 May press release the Woods Hole Oceanographic Institution reported that scientists from multiple institutions and universities took part in an expedition to the Northern East Pacific Rise (EPR) at 9.8°N, an area about 1,300 miles west of Costa Rica, and observed a seafloor eruption. On 28 April a team of scientists aboard the Alvin submersible observed a vibrant ecosystem at the Tica hydrothermal vents, ~2,500 m below the surface, including tubeworms, mussels, crabs, fish, and many other animals. During another dive the next day they noted particulate matter in the water column and slightly elevated temperatures. They turned on the lights and saw that Tica was barren, with dead stands of tubeworms covered in fresh basalt and flashes of incandescence indicating ongoing eruptive activity. The dive was aborted, and planned future dives during the length of the expedition were cancelled due to the safety concerns surrounding the eruption. Scientists continued to gather data at Tica by lowering instrumentation into the water until the end of the expedition on 3 May. Precursory activity including rising temperatures and changes in water chemistry at the vents recorded by previously installed instrumentation.

Geological Summary. A series of dives with the submersible Alvin in 1991 on the East Pacific Rise at about 9°50'N detected evidence for a very recent, possibly ongoing, eruption. Hot-vent animal communities documented during November-December 1989 had been buried by fresh basaltic lava flows, and the scorched soft tissues of partially buried biota had not yet attracted bottom scavengers. Fresh black smoker chimneys and new lava flows were present. This site is south of the Clipperton Fracture Zone at a depth of about 2,500 m, and about 1,000 km SW of Acapulco, México; the south end of the Lamont Seamount chain is about 10 km NW. This is also the location where lava flows previously estimated as being less than roughly 50 years old had been found. Later dating using very short half-life radionuclides from dredged samples confirmed the young age of the eruption and indicated that another eruptive event had taken place in late 1991 and early 1992. An eruption in 2005-2006 produced lava flows that entrapped previously emplaced seismometers.

Source: Woods Hole Oceanographic Institution