A Seiche is a standing wave in a body of water that is at least partially enclosed. They occur mostly on lakes, but ocean bays sometimes experience them as well. It consists of a long wave that reflects from one side of the enclosure to another, sometimes amplified by earthquake activity. Seiches can cause damage and even death if they strike boats or wash onto shore, but do not contain the same power as a tsunami; seiche activity is usually slower and does not displace as much water as a tsunami. Enclosed lakes contain constant seiche activity on a very minimal basis, usually unnoticeable unless there is no wind or other weather to disturb the water; this comes from the natural movement of the water and waterlife inside it, as well as the feeding and draining of the lake through its associated rivers, which keeps the water in motion. Storms on the North American Great Lakes can cause large seiche activity, and can damage both boats and shoreline structures, but seiches cannot come close to the sheer destructive power of a tsunami.