The submarine rift zone west of Cerro Azul volcano is littered with pillows, not the soft kind you sleep on: pillow lava. When it erupts on the seafloor it twists and turns forming balloon-shaped rocks the size of bowling balls, ovens or even as large as sofas. Flows of pillow lava pile-up onto each other creating mounds a few meters to tens of meters tall.

Dragging the dredge over this irregular terrain is a difficult and chancy business. Still, dredging is a standard tool that marine geologists use to gather rocks from the deep seafloor. “We always hope to get stuck - a little bit - in order to break off rocks and catch them in the dredge bag,” Dan Fornari says. “But getting really stuck is a big problem. That’s when you get anchored to the seafloor.”

When the dredge’s teeth dig into seafloor, parts of the lava flow break off and are collected. But sometimes the lava doesn’t let go.

“We’ve got a bite,” Joe Licciardi says. Instead of grinding along the seafloor the dredge has gotten stuck on a rock ledge or large formation of pillow lava.

The eyes around the computer lab turn to the tensiometer recorder near the winch control. The needle jumps across the paper. The tension on the trawl wire rises from 3,000 pounds to 5,000 pounds then 6,000 pounds.

“That’s a big bite,” Mark Kurz says.

We wait for the tension to slack off, but it continues to rise. In less then a few seconds it has jumped to 8,000 pounds. We just started a 1,200-meter-long game of tug-o-war with the seafloor.

We pay out more trawl wire to relieve some of the tension. Dan Fornari calls the bridge to reverse the ship’s direction. “We want to give the dredge plenty of slack so it will drop away from the outcrop, paying out wire and moving the ship 50 to 100 meters backward usually works.”

After a few back-and-forth pulls and releases, the tension on the trawl wire reaches as high as 19,000 pounds before the needle jumps back to 3,000 pounds indicating normal tension. The dredge comes unstuck from the seafloor lava flow - this time, and we continue up the slope.

“That’s as high as I’ve ever seen the tension go before,” Josh Curtice says. “And that’s why we always have someone watching the tensiometer.”

Meanwhile, down on the seafloor, we hope that a nice glassy chunk of pillow lava has dropped into the dredge bag to add to our fantastic collection of seafloor lava from the slopes of Galápagos volcanoes.

Dive and Discover Water Word Puzzle [Click here for a printable version of Dive and Discover Picture Puzzle] Check back tomorrow for the solution.

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