Thor's Well ("the drainpipe of the Pacific"), Oregon

On the rocky shoreline below Cape Perpetua, there's a hole in the rock that looks like it's draining the ocean. Waves wash across the dark basalt shelf and pour into it from every side, vanishing down the opening. Then, just as suddenly, the hole erupts, blasting water back into the air. It's called Thor's Well, and photographers have made it one of the most recognizable sights on the Oregon coast. Its nickname, "the drainpipe of the Pacific," makes it sound bottomless. It isn't. Researchers think Thor's Well began as a sea cave. Over a very long time, waves pounded into the volcanic basalt that forms this stretch of coast and hollowed out a cavern. Eventually the cave's roof collapsed, leaving an opening at the top, while the bottom of the cave stayed connected to the ocean. The hole is estimated to be only about 20 feet deep. That underwater connection is the whole trick. When a wave rolls in, water rushes into the cave from below and surges up through the opening, sometimes spraying as high as 20 feet. When the wave pulls back, the water drains down and out through the bottom. From the surface, the effect looks like the ocean is disappearing into the rock. The show depends on the tide. At low tide the well sits mostly quiet. As high tide approaches, waves start washing over the shelf and the well begins to fill and erupt. The height of the tide and the size and direction of the swell decide how dramatic it gets. That same power makes it dangerous. Waves can surge across the rock shelf with little warning, and people standing too close have been knocked down. Along with nearby Spouting Horn and Devil's Churn, Thor's Well is one of the most spectacular and most hazardous features on this stretch of coast. Cape Perpetua itself rises more than 800 feet above the sea. The Forest Service created the scenic area and its visitor center in the 1960s to protect this stretch of shoreline. Below it, the ocean keeps filling Thor's Well and draining it again, wave after wave.