Isthmus of Panama
The Isthmus of Panama (Spanish: Istmo de Panamá), also historically known as the Isthmus of Darien (Istmo de Darién),[1][2] is the narrow strip of land that lies between the Caribbean Sea and the Pacific Ocean, linking North and South America. It contains the country of Panama and the Panama Canal. Like many isthmuses, it is a location of great geopolitical and strategic importance.
The isthmus is thought to have been finally formed around 3 million years ago (
History
Silver and gold from the
The
Geology
A significant body of water (referred to as the
The Isthmus of Panama is not the only part of central America that has been low lying in the last tens of million years. This means the date of first closure and final closure of the Central American Seaway before it was artificially reopened to a degree by the Panama Canal is likely to remain controversial as noted by those who proposed 15 Ma for first closure except for narrow passages on geological grounds[12] and suggestions that final closure might be more recent based on genetic drift data of black mangroves along the Atlantic and Pacific coasts.[13][relevant?]
Over time, massive amounts of sediment from North and South America filled the gaps between the newly forming islands. Over millions of years, the sediment deposits added to the islands until the gap was completely filled. By no later than 4.5 Ma, an isthmus had formed between North and South America.[citation needed] However, an article in Science magazine stated that zircon crystals in middle Miocene bedrock from northern Colombia indicated that by 10 Ma, it is likely that instead of islands, a full isthmus between the North and South American continents had already formed where the Central American Seaway had been previously.[14] A genomic study of army ants also suggests that the isthmus emerged millions of years earlier than had long been thought.[15]
However the process of formation of the isthmus and its implications is geologically and ecologically more nuanced. There is isotopic and carbonate deposition rate evidence that deep water connections below 1,800 m (5,900 ft) were broken between the Atlantic and Pacific by between 12 and 9.2 Ma.[3] However exchange of surface water so as to maintain western Atlantic salinity at eastern Pacific values continued until about 4.6 Ma with current Caribbean values being reached by about 4.2 Ma although there seems to have been a last definite temporary breach as recently as 2.45 Ma.[3][16] The ocean sediments between the volcanoes on the isthmus seem to have been laid down as recently as 3.1 Ma and the exchange of organism gene pools between the two oceans appears to have continued until about 3 Ma as well.[3] The largest exchange of animals over the land bridge only happened after this time, although some species had made the crossing earlier, perhaps by rafting or brief periods of connection separated by periods of a high water flow between an arc of volcanic islands not conducive to swimming or rafting.[3]
Evidence also suggests that the creation of this land mass and the subsequent warm, wet weather over
The formation of the Isthmus of Panama also played a major role in biodiversity on the planet. The bridge made it easier for animals and plants to migrate between the two continents. This event is known in paleontology as the Great American Interchange. For instance, in North America, the opossum, armadillo, and porcupine all trace back to ancestors that came across the land bridge from South America. Likewise, bears, cats, dogs, horses, llamas, and raccoons all made the trek south across the isthmus.
Biosphere
As the connecting bridge between two vast land masses, the Panamanian biosphere is filled with overlapping fauna and flora from both North and South America. There are, for example, over 978 species of birds in the isthmus area.[17] The tropical climate also encourages a myriad of large and brightly colored species, insects, amphibians, birds, fish, and reptiles. Divided along its length by a mountain range, the isthmus's weather is generally wet on the Atlantic (Caribbean) side but has a clearer division into wet and dry seasons on the Pacific side.
See also
References
Citations
- ^ "BBC - History - British History in depth: The Darien Venture". www.bbc.co.uk.
- ^ "The Darien Scheme". Historic UK.
- ^ PMID 27540590.
- ^ Osborn 1910, pp. 80–81
- ^ Wegener 2003.
- PMID 25918375.
- S2CID 30231555.
- ^ Montes et al. 2015.
- ^ Donovan, Kelly (20 March 2009). "Isthmus of Panama formed as result of plate tectonics". Florida Museum of Natural History.
- ^ Andagoya, Pascual de (21 June 1865). "Narrative of Pascual de Andagoya". Narrative of the Proceedings of Pedrarias Davila. The Hakluyt Society – via Wikisource.
- ^ Wafer 1729
- .
- S2CID 109795658.
- ^ Montes et al. 2015
- ^ Golembiewski, Kate (25 October 2016). "Ant Genomics Help Reshape Biological History of the Americas". Retrieved 8 January 2022.
- S2CID 199095294.
- ^ Angehr & Dean 2010
General sources
- Angehr, G. R.; Dean, R. (2010). The Birds of Panama: A Field Guide. Zona Tropical Publication. Comstock Publishing Associates, Cornell University Press. ISBN 978-0801476747.
- Montes, C.; Cardona, A.; Jaramillo, C.; Pardo, A.; Silva, J. C.; Valencia, V. (2015). "Middle Miocene Closure of the Central American Seaway". PMID 25859042.
- "North and South America Came Together Much Earlier Than Thought: Study". NBC News. Reuters. 9 April 2015.
- O'Dea, A.; Lessios, H. A.; Coates, A. G.; Eytan, R. I.; Restrepo-Moreno, S. A.; Cione, A. L. (2016). "Formation of the Isthmus of Panama". PMID 27540590.
- Osborn, H. F. (1910). The Age of Mammals. Macmillan.
- Wafer, L. (1729). A New Voyage and Description of the Isthmus of America (1695). Scotland: James Knapton. Archived from the original on 3 July 2007. Excerpt from the 1729 Knapton edition
- Wegener, A. (2003) [1912]. "The Origins of Continents" (PDF). Milestones in Geosciences. Translated by Roland von Huene. Berlin, Heidelberg: Springer: 4–17. ISBN 978-3-642-07919-1. (Original German article from 1912 with English translation from 2003.)
External links
- Media related to Isthmus of Panama at Wikimedia Commons