(Pacific City, OR) -- A sink hole has opened in the sand at Cape Kiwanda State Natural Area. It's 20-feet wide and 15-feet deep. The area around the sinkhole has been closed. Oregon State Parks and Recreation says the Cape is a dynamic environment and the sink hole could grow. The Cape is a sandstone outcropping which is weaker than hard rock and subject to sudden changes. They're asking visitors to stay away from the sink hole.