20 The Tropical Pacific Coast of Mexico
F.J. FLORES-VERDUGO, G. DE LA LANZA-ESPINO,
F. CoNTRERAS EsPINOSA, and C.M. AGRAZ-HERNANDEZ
20.1 Introduction
The tropical Pacific coast of Mexico (Fig. 20.1) between the Piaxtla sandbars and the Guatemalan border extends for 2,530 km along the shores of
southern Sinaloa, Nayarit, Jalisco, Colima, Michoacan, Guerrero, Oaxaca,
and Chiapas State (Contreras-Espinosa 1993). The region is tectonically
influenced by the Cocos Plate and classified as a collision coast. The dominant geological features are quaternary alluvial plains, metamorphic rocks
as well as cretaceous igneous and calcareous sedimentary rocks. The continental platform is narrow (12-25km) but widens to 50-75km along the
coast of Sinaloa, Oaxaca, and Chiapas. Much of the coast is composed of
continuous sand beaches interrupted only by rivers and lagoon inlets. Between Jalisco and Oaxaca the coast is predominantly rocky with narrow
beaches and small lagoons surrounded by mangroves. With the exception
of the Santiago and Balsas rivers, most of the approximately 70 rivers have
small drainage basins and seasonally intermittent flow (Arriaga-Cabrera
et al. 1998b ). Approximately 32 barred inner shelf coastal lagoons
(2,545 km 2 ) as well as mangroves and freshwater wetlands comprise
important ecosystems.
20.2 Climate
The climate ranges from semi-arid to humid (Chiapas), though most of the
region is dry sub-humid (800-1,200mm year- 1 ; Garcia 1973). Winds from
the north-west ( <6 m s- 1 ) prevail during the winter (November-April)
along the Sinaloa and Nayarit coast while S-SW winds, which are related to
tropical depressions and hurricanes, dominate as far south as Oaxaca.
Strong northerly winds ("northers"), which originate in the Gulf of MexiEcological Studies, Vol. 144
U. Seeliger and B. Kjerfve (eds.)
Coastal Marine Ecosystems of Latin America
© Springer-Verlag Berlin Heidelberg 2001
F.J. FLORES-VERDUGO, G. DE LA LANZA-ESPINO,
F. CoNTRERAS EsPINOSA, and C.M. AGRAZ-HERNANDEZ
20.1 Introduction
The tropical Pacific coast of Mexico (Fig. 20.1) between the Piaxtla sandbars and the Guatemalan border extends for 2,530 km along the shores of
southern Sinaloa, Nayarit, Jalisco, Colima, Michoacan, Guerrero, Oaxaca,
and Chiapas State (Contreras-Espinosa 1993). The region is tectonically
influenced by the Cocos Plate and classified as a collision coast. The dominant geological features are quaternary alluvial plains, metamorphic rocks
as well as cretaceous igneous and calcareous sedimentary rocks. The continental platform is narrow (12-25km) but widens to 50-75km along the
coast of Sinaloa, Oaxaca, and Chiapas. Much of the coast is composed of
continuous sand beaches interrupted only by rivers and lagoon inlets. Between Jalisco and Oaxaca the coast is predominantly rocky with narrow
beaches and small lagoons surrounded by mangroves. With the exception
of the Santiago and Balsas rivers, most of the approximately 70 rivers have
small drainage basins and seasonally intermittent flow (Arriaga-Cabrera
et al. 1998b ). Approximately 32 barred inner shelf coastal lagoons
(2,545 km 2 ) as well as mangroves and freshwater wetlands comprise
important ecosystems.
20.2 Climate
The climate ranges from semi-arid to humid (Chiapas), though most of the
region is dry sub-humid (800-1,200mm year- 1 ; Garcia 1973). Winds from
the north-west ( <6 m s- 1 ) prevail during the winter (November-April)
along the Sinaloa and Nayarit coast while S-SW winds, which are related to
tropical depressions and hurricanes, dominate as far south as Oaxaca.
Strong northerly winds ("northers"), which originate in the Gulf of MexiEcological Studies, Vol. 144
U. Seeliger and B. Kjerfve (eds.)
Coastal Marine Ecosystems of Latin America
© Springer-Verlag Berlin Heidelberg 2001