The Galápagos archipelago has a unique underwater foundation that is not often studied. Using new high-resolution survey and sampling techniques, researchers led by the Woods Hole Oceanographic Institution (WHOI) conducted the first scientific expedition to explore the deep-water seamounts - or underwater mountains - surrounding the remote Pacific Ocean island chain.
"The well-known islands comprise only about five percent of the volume of the Galápagos, while the massive submarine volcanic platform is largely unexplored," Adam Soule, a geologist at WHOI and chief scientist on the expedition, explained in a news release. "That's part of what makes this work so exciting."
The Galápagos archipelago is made up of 13 major volcanic islands and occupies a submerged platform, which rises more than three kilometers above the adjacent seafloor.
Researchers aboard the M/V Alucia - a heavy lift ship, specifically built with a special platform for diving and submersible operations - surveyed and mapped the area using a multibeam sonar mounted on Alucia's hull and a side-scan sonar fitted to the WHOI-designed autonomous underwater vehicle (AUV), REMUS 600.
Additionally, researchers conducted high-resolution photographic surveys using the WHOI-MISO TowCam deep-towed camera sled system. These surveys helped guide dives, from which researchers were able to collect valuable geological and biological samples.
In total, the high-resolution maps revealed nearly 70 seamounts surrounding the archipelago - many of which are new to science. Furthermore, researchers were able to collect more than 150 rock samples and 300 biological samples, which have since been cataloged and are undergoing analyses.
"We will be conducting geochemical analyses on the samples to determine the link between the volcanic systems below and above the waterline," Dorsey Wanless, one of the study researchers and an assistant professor from Boise State University, added.
Based on preliminary observations of the seafloor rocks, researchers confirm the seamounts emerged during a period of low sea level corresponding to the last ice age about 26,000 years ago. A potential link between sea level changes and eruption rates was also revealed in their analysis, which Soule says could help explain the evolution and past movements of animals between the islands.
"We've just begun to scratch the surface as far as characterizing this environment," Dan Fornari, a marine geologist at WHOI, continued. "We've mapped only about 10 percent of the platform, and already we see tremendous value in how these types of studies can inform our understanding of the Galápagos archipelago."
With further study, researchers hope to learn more about the magmatic processes on the Galápagos Platform, which is currently based almost exclusively on samples from the volcanoes collected on land.
An added bonus of the expedition was the discovery of a new species of catshark. Therefore, study results will also help conservationists better manage the Galapagos Marine Reserve (GMR).
"Seamounts are biodiversity hotspots and essential stepping stones for migratory species, including many threatened shark, turtle and cetacean species," Pelayo Salinas de León, senior marine ecologist at the Charles Darwin Foundation, said. "We still have many months of samples and data analyses ahead of us, but this expedition highlights the need to include some of these seamounts as protected areas in the ongoing re-zoning of the GMR."
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