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
Climate of Mexico rainfall totals are between in most of the major populated areas of the southern altiplano, including Mexico City and Guadalajara. Low-lying areas along the Gulf of Mexico receive in excess of of rainfall in an average year, with the wettest region being the southeastern state of Tabasco, which typically receives approximately of rainfall on an annual basis. Parts of the northern altiplano, highlands and high peaks in the Sierra Madres receive yearly snowfall. Citlaltépetl, Popocatépetl and Iztaccíhuatl continue to support glaciers, the largest of which is the Gran Glaciar Norte. Mexico has pronounced wet and dry seasons. Most of the