Image courtesy of Tim Shank, WHOI

From: Eric Simms
East Pacific Rise, January 24, 2007

Volcanoes of the deep sea

Hello again, from 9°50'N in the east Pacific Ocean (also known at the East Pacific Rise or EPR)!

Did you know that deep beneath the surface of the ocean lies a mountain chain that stretches around the planet, like the seams on a baseball? This underwater mountain is called the mid-ocean ridge, and it forms where plates that make up the Earth’s crust are spreading apart from one another (remember learning this in Earth Science class?). Large cracks in the seafloor also form here, allowing seawater to seep down as much as several kilometers into the crust. As this seawater gets closer to the hot mantle, it heats up, changes its chemistry and then returns to the seafloor surface as super heated fluid, jetting out through hydrothermal vents. The fluids from these vents are rich in chemicals and minerals that support communities of very unique organisms, such as the bacteria, large tubeworms, and crabs you see in the picture above!

Occasionally, magma below the crust erupts up through the cracks and spreading plates and onto the seafloor where it cools quickly to create new crust. Thanks to our scientists who study underwater earthquakes, we learned that an eruption happened here at the East Pacific Rise around January 2006. These lava eruptions can cover the vents as well as the animals living there, leaving only new rock behind. On this cruise, our scientists are trying to better understand how the seafloor has changed since last January, and how organisms arrive to colonize new vent areas. We are using the deep submergence vehicle Alvin to visit the seafloor 2500 meters below, and collect samples and set up new experiments. Read more about it in our cruise logs on the SEAS website:

Come along for the ride!

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Postcards from the Field: Deep Sea

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