Explore the Deep Sea


East Pacific Expeditions

The East Pacific Rise

Map showing position of East Pacific Rise and study site

The East Pacific Rise is a mid-ocean ridge that runs from the Gulf of California to South of Easter Island in the Pacific Ocean (see map, left).

The East Pacific Rise has been studied since the 1980s. Scientists are especially interested in this mid-ocean ridge because the two tectonic plates involved (the Pacific and the Cocos Plates) are moving apart at one of the fastest rates known anywhere on Earth: about 11cm (4.5 inches) a year.

Long-term study site

Scientists associated with the Ridge 2000 research program have been investigating a particular section of the East Pacific Rise for several years. This section — which is often referred to by its latitudinal position (8-11°N) — is one of three sites being studied intensively as a system. It was chosen as a study site for several reasons, including:


With the support of the National Science Foundation, scientists are carrying out especially detailed studies at a so-called "bulls-eye" site. Many hydrothermal vents have been found in this 3.7km-long section of mid-ocean ridge. Moving out from the bulls-eye, there are various geologic features of interest, such as:

Volcanic eruptions followed by recolonization

Volcanic eruptions took place at the bulls-eye site in 1991. These covered large areas of seafloor in new lava, wiping out any animals that had been present.

But within a few years, a wide variety of microbes and animals had colonized the bare rocks. Scientists monitoring this colonization recorded a rich succession of living creatures (photos, right).

Scientists have learned a lot about the different animals by watching the turnover in the different species at the site. They are also conducting experiments to test some theories that the observations prompted. For example, one group of biologists has placed identical blocks of basaltic rock in locations with different temperatures and chemical characteristics. By observing what animals settle and grow in these new habitats, they will learn more about how different types of biological assemblage form.

New eruption in 2006

In 2005, scientists began to predict another eruption at the bulls-eye site. Earthquake activity, together with other observations, pointed towards a fairly imminent event. And in April 2006, the predictions turned out to be correct: another eruption did indeed take place, 15 years after the previous event. But it took a quick response and some sophisticated detective work to confirm the timing and extent of the new eruption.

Next: Rapid Reponse Expedition, mid-2006