National Geographic : 1983 Aug
The dynamic delta Bar (silty Delta front S(clayey silts) TIME AND THE RIVER conspired to create the deltaicplain that comprises most of southeasternLouisiana (bottom left). Successive deltas grew and receded through processes illustratedin the diagonalsequence of diagrams. Today's active delta, the Balize, is now Prodelta silty clays) Continentalshelf (clays) 1600 Delta grows rapidly seaward on the Gulf of Mexico's shallow continental shelf. Flooding expands land area. Freshwater marsh plants nourishedby the river take hold. Naturallevees 1400 After a course change that spawned the modem delta, the river reaches the sea and slows, dropping first heavier, then lighter sediments. Silt and sand collect at channel mouths. Natural levees build as floods drop sediments on the banks.