From Wikipedia, the free encyclopedia - View original article
The Isthmus of Panama, also historically known as the Isthmus of Darien, 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 strategic value.
|This section requires expansion. (May 2008)|
Vasco Núñez de Balboa heard of the South Sea from natives while sailing along the Caribbean coast. On 25 September 1513 he saw the Pacific. 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 pirate 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 la Vieja, are preserved and were declared a UNESCO World Heritage Site in 1997.
Scotland tried to establish a settlement in 1698 through the Darien scheme.
The California Gold Rush, starting in 1849, brought a large increase in the transportation of people from the Atlantic to the Pacific. Steamships brought gold seekers from eastern US ports who trekked across the isthmus by foot, horse, and later rail. On the Pacific side, they boarded Pacific Mail Steamship Company vessels headed for San Francisco.
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 Pacific 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 as early as 15 million years ago. 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 (sand, soil, and mud) 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 gaps were completely filled. By about 4.5 million years ago, an isthmus had formed between North and South America.
Scientists believe the formation of the Isthmus of Panama is one of the most important geologic events in the last 60 million years. Though only a small sliver of land relative to the sizes of continents, the Isthmus of Panama had an enormous impact on the earth's climate and environment. By shutting down the flow of water between the two oceans, the land bridge rerouted ocean currents in both the Atlantic and Pacific Oceans. Atlantic currents were forced northward and eventually settled into a new current pattern that we now call the Gulf Stream. With warm Caribbean waters flowing toward the northeast Atlantic, the climate of northwestern Europe and eastern North America grew warmer. (However, it is actually the directly affected atmospheric circulation rather than the Gulf Stream that results in the pronounced temperature differential between Europe and the eastern US.) Evaporation in the tropical Atlantic and Caribbean caused freshwater vapor to enter the atmosphere, while leaving behind salty water. The trade winds (blowing east to west) carried the water vapor and deposited it in the Pacific by precipitation. As a result, the Atlantic became saltier than the Pacific. Each of these changes helped establish the global ocean circulation pattern in place today. In short, the Isthmus of Panama directly and indirectly influenced ocean and atmospheric circulation patterns, which regulated patterns of rainfall, which in turn sculpted landscapes.
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 today, the opossum, armadillo, and porcupine all trace back to ancestors that came across the land bridge from South America. Likewise, ancestors of bears, cats, dogs, horses, llamas, and raccoons all made the trek south across the isthmus. (Many of the South American mammals went extinct. It seems that the North American mammals were more accustomed to competition and better suited to the cooling climate.)
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 coloured species: insects, snakes, 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.
|Wikimedia Commons has media related to Isthmus of Panama.|