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On Thursday, June 11, 2015, marine geologist Gary Greene treated islanders to an absorbing visual tour of the hidden subsea world around the San Juan Archipelago, showing the strikingly beautiful sonar images he has been recording for the past 20 years. Cosponsored by Coates Vineyards and the Northwest Straits Foundation, working with the San Juan County Marine Resources Committee, his Orcas Currents lecture began at 5:30 pm in Orcas Center, with an overflow audience of more than 230 rapt listeners.

Formerly the Director of the Moss Landing Marine Labs on Monterey Bay in California and currently a research faculty member at Friday Harbor Labs, Greene has pioneered sophisticated sonar techniques to map the sea floor in many regions of the Pacific Ocean. Now working with the SeaDoc Society and heading its Tombolo Mapping Lab on Orcas Island, he has been making high-resolution 3D images of the Salish Sea floor. In the process, he has uncovered previously unknown benthic habitats and discovered geological features such as submarine faults and folding.

In his talk, Greene brought alive the deep undersea world around us. Of interest to biologists and ecologists, as well as fishermen, sailors, and kayakers, his exquisitely detailed maps have revealed the habitats of rockfish, Pacific sand lance, forage fish and other organisms critical to the local marine food chain.

Greene has also discovered a significant new geological fault dubbed the Skipjack Island Fault, which begins near South Pender Island and extends eastward to pass between Orcas and Sucia Islands. He discussed his current research on this and other local submarine faults, including whether or not they might be active.

Based on this research and other work, Gary surveyed the region’s recent geological history and addressed what may await us in the future due to potential sea-level rise, tsunami inundation, and oil spills from passing vessels.

In all, it was a stimulating visual voyage into the hidden subsea world surrounding our islands.