Gulf of Mexico numerous bays and smaller inlets. A number of rivers empty into the gulf, most notably the Mississippi River and Rio Grande in the northern gulf, and the Grijalva and Usumacinta rivers in the southern gulf. The land that forms the gulf's coast, including many long, narrow barrier islands, is almost uniformly low-lying and is characterized by marshes and swamps as well as stretches of sandy beach. The Gulf of Mexico is an excellent example of a passive margin. The continental shelf is quite wide at most points along the coast, most notably at the Florida and Yucatán Peninsulas. The shelf
Gulf of Mexico Colorado River as the international boundary, of November 23, 1970; Treaty on maritime boundaries between the United States of America and the United Mexican States (Caribbean Sea and Pacific Ocean), of May 4, 1978, and Treaty between the Government of the United States of America and the Government of the United Mexican States on the delimitation of the continental shelf in the Western Gulf of Mexico beyond , of June 9, 2000. On December 13, 2007, Mexico submitted information to the Commission on the Limits of the Continental Shelf (CLCS) regarding the extension of Mexico's continental shelf beyond 200 nautical