The Isthmus of Panama
The isthmus is thought to have been formed around 2.8 million years ago,
separating the Atlantic
and Pacific Oceans and causing the creation of the Gulf Stream
. This was first suggested in 1910 by North American paleontologist Henry Fairfield Osborn
. He based the proposal on the fossil record of mammals in Central America.
This conclusion provided a foundation for Alfred Wegener
when he proposed the theory of continental drift
Núñez de Balboa's travel route to the South Sea, 1513
Vasco Núñez de Balboa
heard of the South Sea from natives while sailing along the Caribbean coast.
On 25 September 1513 he discovered the Pacific Ocean. In 1519 the town of Panamá was founded near a small indigenous settlement on the Pacific coast. After the discovery of Peru
, it developed into an important port of trade and became an administrative centre. In 1671 the Welsh privateer Henry Morgan
crossed the Isthmus of Panamá from the Caribbean side and destroyed the city. The town was relocated some kilometers to the west at a small peninsula. The ruins of the old town, Panamá Viejo
, are preserved and were declared a UNESCO World Heritage Site
A significant body of water (referred to as the Central American Seaway
) once separated the continents of North and South America, allowing the waters of the Pacific and Atlantic Oceans to mix freely. Beneath the surface, two plates
of the Earth's crust
were slowly colliding, forcing the Cocos Plate
to slide under the Caribbean Plate
. The pressure and heat caused by this collision led to the formation of underwater volcanoes
, some of which grew large enough to form islands
. Meanwhile, movement of the two tectonic plates was also pushing up the sea floor, eventually forcing some areas above sea level.
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 million years ago, an isthmus had formed between North and South America. However, an article in Science magazine
stated that zircon
crystals in middle Miocene
bedrock from northern Colombia indicated that by 10 million years ago, 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.
Evidence also suggests that the creation of this land mass and the subsequent warm, wet weather over northern Europe
resulted in the formation of a large Arctic ice cap
and contributed to the current ice age
. That warm currents can lead to glacier formation may seem counterintuitive, but heated air flowing over the warm Gulf Stream can hold more moisture. The result is increased precipitation that contributes to snow pack.
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
, 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.
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.
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.
- ^ https://www.historic-uk.com/HistoryUK/HistoryofScotland/The-Darien-Scheme/
- ^ O’Dea et al. 2016, Abstract
- ^ Osborn 1910, pp. 80–81
- ^ Wegener 1912
- ^ Andagoya, Pascual de (21 June 1865). Narrative of the Proceedings of Pedrarias Davila. The Hakluyt Society – via Wikisource.
- ^ Wafer 1729
- ^ Montes et al. 2015
- ^ Seager 2006
- ^ Angehr & Dean 2010
- 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". Science. 348 (6231): 226–229. Bibcode:2015Sci...348..226M. doi:10.1126/science.aaa2815. PMID 25859042. Lay summary (25 March 2018).
- 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". Science Advances. 2 (8): e1600883. Bibcode:2016SciA....2E0883O. doi:10.1126/sciadv.1600883. PMC 4988774. 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) . Translated by Roland von Huene. "The Origins of Continents" (PDF). Milestones in Geosciences. Berlin, Heidelberg: Springer: 4–17. doi:10.1007/978-3-662-08763-3_1. ISBN 978-3-642-07919-1. (Original German article from 1912 with English translation from 2003.)
Last edited on 9 April 2021, at 06:19
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