Sea Stack Sea stack along Oregon's northwest coast. Image from USGS Center for Coastal Geology . Sea Stack Sea stacks are blocks of erosion -resistant rock isolated from the land by sea.
Sea stacks begin as part of a headland or sea cliff.
Relentless pounding by waves erodes the softer, weaker parts of a rock first, leaving harder, more resistant rock behind. Jump-off Joe, a sea stack, erode over 100 years. This site is a cooperative project of the US Geological Survey Western Earth Surface Processes Team and the National Park Service .