Explore the Deep Sea
East Pacific Rapid Response Expeditions
In mid-2006, scientists investigated a possible volcanic eruption on the East Pacific Rise, a mid-ocean ridge in the Eastern Pacific.
Time is of the essence
Most research expeditions are planned for months or years. But volcanic events are unpredictable, so when an eruption occurs, scientists need to respond very quickly. Characteristics of the seawater, the sea floor and the biological communities all change — often dramatically — when an eruption takes place. So scientists want to study these changes, and observe them in action if possible. This helps us understand many important processes that help to shape our planet — from the movement of tectonic plates to the creation of deep-sea habitats for animals.
Eruption detected in April 2006
For several years, scientists have been predicting that volcanic eruptions could occur at the East Pacific Rise — a long-term study site in the Eastern Pacific. Now their predictions have turned out to be correct.
Scientists first suspected that an eruption might have taken place when some deep-sea instruments appeared to fail. These instruments (ocean bottom seismometers) had been sitting on the seafloor, around 2500m (roughly 8,125 feet) below the surface of the ocean. They were due to be picked up by an expedition to the site in mid-April 2006. But when expedition researchers instructed the instruments to return to the sea's surface, many of them failed to respond. Could the missing instruments have been buried by lava?
The loss of the instruments, combined with tell-tale changes in seawater near the site, was strong evidence for an eruption. But this group of scientists did not have the equipment or the fuel to stay at the site and investigate further. So, with support from the National Science Foundation, another expedition was put together and set sail in just two weeks. It was important to reach the site as quickly as possible, because eruptions don't happen there very often (the previous one was in 1991), and they may only last for days or weeks.
Rapid response to investigate
This "rapid response" expedition, aboard the Research Vessel New Horizon (left), arrived on site in May 2006.
Scientists looked for evidence of eruptions by:
- Sampling the water above the suspected eruption site to identify any changes in temperature and chemistry which would indicate volcanic activity
- Dredging up rocks from the site to see if any of the rocks were newly-erupted — no mean feat when the seafloor is more than a mile and a half below the ship!
- Photographing the seafloor with a towed camera, to get visual confirmation of new lava flows
Digital photos showed that in some places lava had flowed for nearly a kilometer (0.6 miles) from the eruption site, covering much of the older lava from the 1991 eruption. Many hydrothermal vents previously found in the area appear to have been covered or altered. And the tubeworms, clams and other animals at these sites may have been largely wiped out.
Tectonic activity causes eruptions
On a geologic time scale (many, many thousands of years) volanic eruptions are expected at numerous points along a mid-ocean ridge, as tectonic plates move away from one another. But on a human time scale (years to decades), the time between successive eruptions has been a topic of scientific debate. Now there is evidence that as little as 15 years can separate eruptive activity at any one location.
Stay tuned: more expeditions
The results from the rapid response expedition were so exciting that another expedition was launched. Again supported by the National Science Foundation, researchers returned to the site in late June 2006. This time, they took along a manned submersible, Alvin. Scientists used Alvin to visit the eruption site in person.