Explore the Deep Sea
East Pacific Expeditions
The East Pacific Rise
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:
- Because the tectonic plates are moving apart fast, there is a high chance of some sort of geologic event — such as an eruption, or cracking of rocks in the Earth's crust — occurring within a period of a few years.
- It is relatively easy to access: it is located about 2 days sailing (~500 miles) south of Manzanillo, Mexico, and about 5-7 days sailing south of San Diego, the closest U.S. port.
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:
- Areas where the axis of the mid-ocean ridge (the narrow rift where most volcanic eruptions and hydrothermal activity occurs) shifts sideways by tens or hundreds of metres.
- Bodies of magma within the crust and mantle.
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.