The Great American Biotic Interchange

Volume 4 of the series Topics in Geobiology pp 303-324

Sea Level, Climate, and the Central American Land Bridge

  • Samuel M. SavinAffiliated withDepartment of Geological Sciences, Case Western Reserve University
  • , Robert G. DouglasAffiliated withDepartment of Geological Sciences, University of Southern California

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The development of a land connection across Central America in Neogene time permitted the interchange of terrestrial faunas between North and South America. It also prevented the flow of tropical seawater from the Atlantic to the Pacific Ocean. At the present time there are two low-lying regions that traverse Central America between the two oceans, one in northern Costa Rica and southern Nicaragua and the other across Panama. Today both of these regions would be awash if sea level were only moderately higher—34 m for the northern passage and 84 m for the southern (neglecting the excavations for the Panama Canal). It is possible that crustal motions during the past 15 million years have altered the topography of these two low-lying regions. However, it is fair to say that realistic estimates of eustatic sea level indicate that sea level lowering was an important (perhaps the most important) cause of the emergence of the land connection.