Explosive Volcanism in the Deep


Can a volcano be explosive in the deep sea? What about violent? What about mildly aggravated?

Historically, we’ve assumed the answer to be no. Explosive eruptions were thought to be absent at depths below the critical point for seawater around 3000m. Combine this with the lack of evidence for a pyroclastic deposit [rock materials formed by fragmentation as a result of volcanic action] below 3,000m. On top of that add the hypothesis that mid-ocean-ridge basalts do not possess the volatility to produce impressive eruptions at high pressures.

A group of researchers report this week in Nature provide evidence of pyroclastic deposits on the Gakkel ridge in the Arctic Basin at 4000m. In the abstract the authors note a large area “blanketed” with deposits including bubble wall fragments.

Well…that raises some questions.


Figure 2: a, Frame grab from a high-definition video camera taken on the south side of Duque’s hill (see Fig. 1 for location). About 10 cm (visually estimated and confirmed during sampling) of pyroclastic material is piled atop a high-standing, weathered, pillow feature. The exoskeleton of an as yet unidentified species of hexactinellid sponge23 is visible in the foreground. b, High-definition video frame grab of talus blocks possibly representing ejecta from a vulcanian explosion on Oden volcano (see Fig. 1 for location). c, Glassy, granular, pyroclastic material. d, Bubble wall fragment from pyroclastic deposit.

Dr. M (1748 Posts)

Craig McClain is the Assistant Director of Science for the National Evolutionary Synthesis Center, a National Science Foundation supported initiative. He has conducted deep-sea research for 20 years and published over 50 papers in the area. He has participated in and led dozens of oceanographic expeditions taken him to the Antarctic and the most remote regions of the Pacific and Atlantic. Craig’s research focuses on how energy drives the biology of marine invertebrates from individuals to ecosystems, specifically, seeking to uncover how organisms are adapted to different levels of carbon availability, i.e. food, and how this determines the kinds and number of species in different parts of the oceans. Craig’s research has been featured on National Public Radio, Discovery Channel, Fox News, National Geographic and ABC News. In addition to his scientific research, Craig also advocates the need for scientists to connect with the public and is the founder and chief editor of the acclaimed Deep-Sea News (http://deepseanews.com/), a popular ocean-themed blog that has won numerous awards. His writing has been featured in Cosmos, Science Illustrated, American Scientist, Wired, Mental Floss, and the Open Lab: The Best Science Writing on the Web. His forthcoming book, Science of the South (http://www.scienceofthesouth.com/), connects cultural icons of South such as pecan pie with the science behind them.

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