Central and South America¶
Contents
This page is devoted to the Latin countries of Central and South America. Vegetation cover ranges from desert to forested mountains to subtropical lowlands.
Central and South America
We head now south of the U.S. border into northeast Mexico, in the States of Nuevo Laredo and San Luis Potosi (left two-thirds of the image below) and Tamaulipas (right). The strongly folded sedimentary rocks of the Sierra Madre Orientale run through the center of the scene. Coastal plains make up the area to the east and semi-desert at high elevations occupies the land to the west. The reds denote regions that can experience 30 inches (75 cm) of rainfall each year owing to moisture moving inland from the Gulf of Mexico. This is a monsoonal climate, with wet, hot summers and dry cold winters. The plains supports typical subtropical savannah vegetation and the mountains are havens of both broadleaf and coniferous trees. The arid interior to the west is host to brushy plants and cactus.
forests to the east and a barren desert landscape in the lowlands to the west.|
On to central Mexico and a peak at the oldest city in the Western hemisphere, the present day Mexico City, built on a site where in the 12th century stood Tenochitlan, inhabited continuously since then. Mexico City now is seen as a blue area in the upper left part of the image. In 1973, M.C. had just over 7 million but has grown so rapidly that it will approach 30 million early in the 21st Century. Parts of the city stand on swampy ground and lake beds, particularly susceptible to failure and building collapse during the strong earthquakes that frequent the region. To its east are a line of active to dormant volcanoes, marking the surface expression of subduction of the Pacific plate under the North American plate.The two biggest volcanoes are Istaccihuatl and Popocatepetl, both snow-capped in this May scene, that lie to the southeast of M.C. Their slopes, and highlands elsewhere, are forested (reds) but most of the land is arid and sparsely vegetated. Most of the region shown is elevated - at 2800 m (7500 ft) at M.C. and higher.
lands in central Mexico.|
This Landsat-7 subscene, acquired on March 21, 2000, shows the city in more detail
Combining Landsat and DEM data yields this perspective view of Mexico City. The two volcanoes appear to its south-southeast. The ring of hills around much of Mexico City indicates why it is often a smog-drenched city since winds may be too blocked to drive the gases away.
We move into Central America through Guatemala into Nicaragua. Its western part, against the Pacific Ocean, appears below. The larger body of water inland is Lake Nicaragua, with several volcanoes on islands within. In the upper left is Lake Managua, with the capital city, Managua, along its south shore. Circular lakes are fillings of central vents or calderas. The lower elevations consist of semi-arid vegetation, with some farmlands. Areas of red represent uplands with forest cover, with more mountainous highlands at the upper right corner.
As we approach the South American continent, we pass over in this Landsat-DEM perspective image the “Big Ditch” that was one of President Teddy Roosevelt’s greatest accomplishments - the Panama Canal, which rivals the Suez Canal (see page ) as the greatest aid in oceanic navigation.
Unlike the earlier Suez Canal, the Panama Canal requires a series of locks to acommodate the difference in sea level heights between the Atlantic (Gulf of Mexico) Ocean and the Pacific Ocean (the Pacific is about 5 meters higher). A boat enters a lock, behind it another lock gate swings shut, and water is pumped in to raise the boat level to that of the next lock entered. Here is a diagram of this lock system:
Staying in the Carribean but now touching the northern coast of South America, this next scene is an Envisat-MERIS image of parts of Venezuela and Columbia to its west:
The greenish water off the Carribean is the Gulf of Venezuela. A narrow strait passes south into Lake Maracaibo, within and around which ar most of the oil fields that make Venezuela the fifth largest petroleum producer in the world. On its west side is the Sierra de Perija whose crest forms the border with Columbia. Along the eastern shore of Maracaibo is the Cordillera de Merida. Both mountain systems are the northern extension of the Andes. The west mouth of the Gulf of Venezuela is formed by the Guajira Peninsula. An island like body on the east side is the Paraguana Peninsula, joined to the mainland by such a narrow strip of land as to be almost invisible in this image. The island of Curacao (famed for its liqueur of that name, made from sour orange peels, and as a stop for Carribean cruise ships) lies to the east. Caracas, the Venezuelan capital, is just off the image on the upper right side.
Our travels take us now along the west coast of South America. The dominant landform features in western South America are the mighty Andes Mountains. These are part of the general cordillera that lines the western regions in both Americas and Central America. The Andes are uplifted mountains, involving intense folding, faulting, and volcanism on the continental tectonic plate as it is subducted by the east moving, incoming Pacific tectonic plate. In this image in southern Peru, a dry desert appears blue. The land rises abruptly eastward in dissected mountains whose elevations range to altitudes from 4300 to 5500 meters (14000 to 18000 ft; the highest peaks in the Andes approach 23000 ft). Progressing to the northeast, the terrain is first dissected, then gives way to a broad, flatter Altiplano, and ends (upper right) in the High Andes.
The highest peak in the South American Andes is Mt. Aconcagua (6982 m or 22840 ft) in Argentina, shown in this Landsat 5 image:
The next view covers a very sparsely populated segment of southern Peru (top) and northern Chile. The bluish-gray stretch of lands from the coast inward in part of the Atacama Desert, notorious as one of the driest regions on Earth. The desert results from the “drying out” of moisture in air masses crossing the Andes, which leds to rains and heavy snows. Some places in this desert, which continues well to the south, have seen as little as 1 inch of rain in five years. But, note that a few river valleys have ribbons of red indicating some vegetation (in oases where small villages can subsist), fed by occasional water coming from the better water uplands of the volcanic Cordillera Occidentale that comprises the western extent of the Andes. (See if you can find the large volcano in this image.) Note the landforms against the Andes flanks which are yellowish-brown - these are huge, coalesced alluvial fans now being dissected.
The desert is replaced by vegetation (some cultivated) in the lowlands extending inward from the Pacific. In this Landsat-7 ETM+ image, Chile’s capital of Santiago appears as a dark-gray area in the green valley surrounded by coastal ranges to the west and the Andes to the east.
Moving across the Andes, Western Argentina occupies the scene below. Along the left margin is the eastern terminus of the High Andes, with ridges above 4800 meters (16000 ft), and surface with few extended forests but with some brushy vegetation. A large alluvial fan, in blue, appears near the upper left; at its eastern (right) margin is a conspicuous area of red-rendered vegetation which marks a zone where subsurface and surface waters from snow melt in the Andes passes onto the high plains. Lake Ilancanedo is seen to its southeast, a body of water that varies considerably with the seasons (in March, for this scene, the southern Fall is drier and the lake has shrunk). The landscape at this time of year shows minimum active plant growth. The volcano Cerro Nevado, with its snow cover giving the clue that it is high (3700 m; 12000 ft), seems isolated from the Andes. The caldera topping Cerro Payun (near bottom center) lies east of a broad field of basaltic volcanism.
Using a combination of a Landsat image and SRTM elevation data, a perspective of the Andes in Argentina gives an impression of their great heights:
Buenos Aires, Argentina’s capital, has been called the “Paris of South America” because of its bright, clean buildings (despite a Shanty Town within its limits) and planned layout. This city of 11 million lies on the Rio Plata’s estuary; to its north is Uruguay. Let’s first look at its skyline:
Here is a 15 m Landsat-7 ETM image of the region, including the north end of the Pampas (plains land noted for its favored grazing of beef cattle):
Part of the central city as seen at 4 meters by IKONOS shows the rectangular block layout of Buenos Aires:
Rio de Janeiro, the Queen city of Brazil, spreads out from the western shore of Guanabara Bay, along the coast (the city, in black, lies above center right). The low Serra do Mar passes through this area. The Serra de Orgaos, up to 1000 m (3000 ft) lies to the north. Similar low mountain terrain extends to the west. An evergreen rain forest lines the coast but mixes with semideciduous and mountain vegation further inland. Compare the vegetative cover here with that of the Amazon Basin, shown on page 3-5. Note the narrow strip of land (near image center) made up of marine deposits that encloses the Baia de Sepetiba. Brazil�s second city, Sao Paulo, is situated on the coast in the image along the next westward orbit below the lower left corner of this scene.
This Landsat-7 ETM+ image shows much more detail within Rio de Janiero:
This city is the jewel of South America. This ground photo shows only part of the area of high rises set against the background of the Bahia Guanabara and the famed Sugarloaf mountain with its tall statue of Christ with arms outstretched:
Now let’s head east and cross the Atlantic Ocean.