We’re looking for another way to help date when eruptions occurred in the western Galápagos. Volcanologists always want to know when eruptions happen, both now and in the distant past.

If Galápagos volcanoes spewed volcanic material high into the air during previous eruptions, wind currents could have sent the dust, ash and small particles of volcanic rock out over the ocean where they would drift down to the seafloor. Thin layers of volcanic ash in marine sediments provide good evidence for eruptions. Small shells of animals and plants in the sediment above and below the ash allow us to get accurate dates.

Denny Geist, Mark Kurz and their students have walked around many areas on Isabela and Fernandina. They have seen evidence of eruptions that occurred before recorded history, as far back as 300,000 years ago.

To find out if these ancient eruptions sent ash and dust into the sky we needed some ingenuity. We can’t just go around the corner to a store or order a piece of equipment online.

To pick up the sediment we need something like a tube. “What we need is a small sediment corer,” Denny Geist says, “something that can just punch through the upper meter or so of sediment so that we can see if there are any ash layers.”

What we have on board is a rock corer. A piece of equipment we have used to collect glass from the surface of seafloor lava flows. The trick is whether it can be modified to collect sediment instead of glass.

“Dan wanted to know if we could convert his rock corer into a sediment corer,” Todd Ericksen says. “Basically you have a pipe that plugs into the seafloor and traps the sediment as it pulls back out. He described what a corer should look like and I tried to build it from what we had.”

Todd found an old flexible hose that fit inside the rock corer and made a core catcher for the tip out of some thin strips of stainless steel. The core catcher allows sediment into the hose but prevents it from falling back out on the way to the surface. Then he used a brass fitting for a nose cone to hold the core catcher in place. “Once I made it, I was hoping they would use it,” Todd says. “I’ve actually never seen a sediment corer before.”

After bashing into the seafloor at 80 meters per minute and being hauled up, the corer appeared on the surface. Once on deck, everyone gathered around. There was sediment on the tip but none in the tube. After removing the core catcher we realized why. The corer hit a hard layer of glassy volcanic gravel that stopped it from going very far into the sediment. Inside the core catcher we found gray-green sediment and bits of volcanic glass - great samples but not the ash we were looking for. If we have time we will try it again.

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

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