Blowholes are a common feature on many volcanic islands and along the Oregon coast such as at Depoe Bay. A blowhole or marine geyser is formed as sea caves erode and undercut overlying rock. Vertical shafts may develop as the roof of the sea cave erodes or collapses to expose the surface and creating a vent. Hydraulic compression of sea water entering the sea cave is released through the vent resulting in a marine geyser. The geometry of the cave and blowhole along with tide levels and swell conditions determine the height of the spray. Read more here and here. See a short video here. Click here to download the CoastView app and explore Depoe Bay and the Oregon coast.