<descriptor thcode="62"><thesaurus thcode="62" name="Coastal and Marine Ecological Classification Standard" scope="Categories of ecosystems for coastal, estuarine, and marine environments." creator="FGDC" rights="public domain" date="2017-05-10" codetype="alpha" prefix="cmecs" uri="https://www2.usgs.gov/science/CMECS" tblname="cmecs" root_code="root" contact="pschweitzer"><category><term thcode="25" code="16" name="hierarchical" parent="11" scope="Substantive broader-narrower relationships exist among the terms."/><term thcode="25" code="16" name="hierarchical" parent="11" scope="Substantive broader-narrower relationships exist among the terms."/></category><altlabel><altlabel>CMECS</altlabel><altlabel>CMECS</altlabel><altlabel>Coastal and Marine Ecological Classification Standard (CMECS)</altlabel><altlabel>Coastal and Marine Ecological Classification Standard (CMECS)</altlabel></altlabel></thesaurus><term thcode="62" code="GC-094" name="Flat" parent="GC-011" scope="Geoform: A general term for a level (or nearly level) surface or area of land marked by little or no relief; flats are often composed of unconsolidated sediments (such as mud or sand). ..."/><bt><term thcode="62" code="GC-011" name="Geologic" parent="GC-C052" scope="Geoform Origin: Geologic geoforms are formed by the abiotic processes of uplift, erosion, volcanism, deposition, fluid seepage, and material movement. ..."/><term thcode="62" code="GC-C052" name="Geoform (levels 1 and 2 subcomponents)" parent="GC-C005"/><term thcode="62" code="GC-C005" name="Geoform" parent="root"/><term thcode="62" code="root" name="CMECS" scope="Coastal and Marine Ecological Classification Standard: Category terms encompassing waters from the head of tide or inland incursion of ocean salinity to the splash zone of the coasts to the deepest portions of the oceans and the deep waters of the Great Lakes."/></bt><nt><term thcode="62" code="GC-095" name="Back Barrier Flat" parent="GC-094" scope="Geoform Type: A subaerial, gently sloping landform on the lagoon side of the barrier beach ridge. These flats are composed predominantly of sand washed over (or through) the beach ridge during tidal surges (modified from Jackson 1997)."/><term thcode="62" code="GC-096" name="Barrier Flat" parent="GC-094" scope="Geoform Type: A relatively flat, low-lying area that is separating the exposed (or seaward) edge of a barrier beach or barrier island from the lagoon behind it. ..."/><term thcode="62" code="GC-097" name="Ebb Tidal Delta Flat" parent="GC-094" scope="Geoform Type: The relatively flat, dominant component of the ebb tidal delta. At extreme low tide, this landform may be exposed for a relatively short period (U.S. Department of Agriculture 2008)."/><term thcode="62" code="GC-098" name="Flood Tidal Delta Flat" parent="GC-094" scope="Geoform Type: The relatively flat, dominant component of the flood tidal delta. At extreme low tide, this landform may be exposed for a relatively short period (U.S. Department of Agriculture 2008)."/><term thcode="62" code="GC-099" name="Tidal Flat" parent="GC-094" scope="Geoform Type: An extensive, nearly horizontal, barren (or sparsely vegetated) tract of land that is alternately covered and uncovered by the tide. Tidal flats consist of unconsolidated sediment (mostly clays, silts and/or sand, and organic materials)."/><term thcode="62" code="GC-100" name="Washover Fan Flat" parent="GC-094" scope="Geoform Type: A gently sloping, fan-like, subaqueous landform created by overwash from storm surges that transports sediment from the seaward side to the landward side of a barrier island (Jackson 1997). ..."/><term thcode="62" code="GC-101" name="Wind Tidal Flat" parent="GC-094" scope="Geoform Type: A broad, low-lying, nearly level sand flat that is alternately flooded by ponded rainwater or inundated by wind-driven marine and estuarine waters. ..."/></nt></descriptor>