Definition
A tidemark is a line or mark left on a shore or bank indicating the high-water mark of a tide. It's a visual record of the sea's reach. Think of it as the ocean's signature on the land. Tidemarks can be composed of seaweed, debris, or a change in color or texture of the sediment. They provide a clear indication of the tidal range in a particular area. Observing tidemarks can reveal information about coastal processes and sea-level changes. It's a simple yet informative natural indicator.