marsh

Lakes and marshy moorland at Thingvellir, Iceland. This is a typical periglacial landscape, which in winter becomes coated in snow and ice.

Low-lying wetland. Freshwater marshes are common wherever groundwater, surface springs, streams, or run-off cause frequent flooding, or more or less permanent shallow water. A marsh is alkaline whereas a bog is acid. Marshes develop on inorganic silt or clay soils. Rushes are typical marsh plants. Large marshes dominated by papyrus, cattail, and reeds, with standing water throughout the year, are commonly called swamps. Near the sea, salt marshes may form.