The western end of the canal system is a natural embayment leading to the Gulf of Panama; the bridge is part of the PanAm highway system that starts in Alaska, proceeds through the western U.S., down all of Central America, and then along western South America into Chile:
Nearby, on the Gulf and the Pacific Ocean, is Panama City. It is now surprisingly modern, with many skyscrapers (the writer [NMS] has been astounded at how many large cities outside the U.S. have such high rise buildings; these will be evident throughout the remainder of this Section.
Our travels next take us through representative parts of South America. This map shows the countries making up this continent and the major geographic land units.
Staying in the Caribbean 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 Caribbean 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. Just above the peninsula in the center is Aruba, shown above. The island of Curacao (famed for its liqueur of that name, made from sour orange peels, and as a stop for Caribbean cruise ships) lies to its east. Caracas, the Venezuelan capital, is just off the image on the upper right side.
Caracas, Venezuela's capital, is nestled between mountains just inland from the Caribbean coast, as shown in this Landsat-7 image:
While in Venezuela, let's look at a remarkable scence in its southern Orinoco Basin. The Orinoco River in this Landsat-1 subscene cuts across a low terrain that is an extension of the Guyana Highlands to the northeast. Look carefully at the image to see a pronouced zig-zag pattern (emphasized by black lakes). The writer (NMS) has not found a reference to this feature; he interprets the pattern to be tight chevron folds in the crystalline rocks that outcrop also in the Highlands.
West of Venezuela are the countries of Columbia and Ecuador. The capital of Columbia, Bogota, is shown in this Geology.com Landsat rendition:
The Andes mountains have their narrowest extent in these countries. Here is a composite image of Ecuador:
In a loose sense South America extends some 500 miles (800 km) into the Pacific Ocean (in reality, beyond the western edge of this continental plate). Ecuador "owns" the famous Galapagos Islands, now a popular tourist attraction. Look first at this image from space in which the islands are labeled and then at an astronaut photo from the International Space Station of part of the Galapagos - volcanic islands all - covering most of Isla Isabela and Isla Fernandino:
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 the longest continuous mountain chain on Earth; they are less than 40 million years old. 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. JPL has prepared a simulated journey along the Andes as a movie using radar data. Access it through the JPL Video Site, then the pathway Format-->Video -->Search to bring up the list that includes "Andes Mountains Flyover", June 20, 2003. To start it, once found, click on the blue RealVideo link.
As we saw above, the Andes tend to be relatively narrow over much of their length. This is evident in this astronaut photo looking eastward across the vegetated coastal plains, then the high Andes and the moderate elevation Pampas of Argentina, which in this wintertime scene is brown because of dry grasslands:
In this Landsat-1 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 Cerro (mountain) 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. Note the landforms against the Andes flanks which are yellowish-brown - these are huge, coalesced alluvial fans now being dissected.
The bluish tones in the Atacama Desert are not true color. The dominant colors are actually browns to reds. We show a more realistic rendition in this ESA MER image; a ground photo also is typical of this landscape:
The capital of Peru is Lima, set along the Pacific coastline, as seen in this Radarsat image:
Between Peru and Chile is Bolivia. Its capital, La Paz, is inland, surrounded by low mountains. Here is a ground scene:
The next two scenes of La Paz are from space, the first a SIR-C radar image, the second a Landsat image. Note that each one contains a long, straight strip. This is the main runway for the airport (named Kennedy, because the United States provided significant funding to build the facility during the Kennedy administration). This lies amidst newer, more suburban parts of La Paz - the older sections are located within the valleys framed by the Andes foothills.
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.
A ground view of Santiago shows the high Andes in the background:
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:
The Andes are a relatively young mountain system. The Chilean segment of the Andes began its major upheaval about 15 million years ago. The eastward subduction of the Pacific plate leads to extensive melting that produces numerous volcanoes (as reported on page 17-3). These lie along the Pacific Ring of Fire. This SIR-C image shows several in northern Ecuador, including the trio Cuan, Mojande, and Imabua, and to their south, Cayambe.
One of the most magnificent volcanoes in South America is Cotopaxi, in Ecuador, not far from the capital, Quito. We look at from the ground first and then in a radar image obtained during the SRTM Shuttle mission which used radar data to reconstruct topography:
The Andes mountains support numerous mountain glaciers. This ASTER scene shows the San Quintin glacier and ice field on the east side of the Andes.
In Argentina, the Andes grade eastward into the 800000 square mile expanse of plateaus and plains of the Patagonia. Here is a Landsat-1 subscene that shows the gradation from the High Andes into Patagonia:
North of Patagonia the land is lower, forming a vast plains known as the Pampas. Here is one of the great cattle ranching regions of the world. This space image shows a typical landscape in winter:
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, at the edge of the Pampas, 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) and the delta and estuary of the Rio Plata. Below it is an astronaut photo (Mission STS-56) that shows some of the details within the city.
Moving north into Brazil, the second largest city is Sao Paulo - more than 10 million citizens. Here is an overhead view of this coastal area:
Like other South American cities, in recent years the central urban area is replete with skyscrapers:
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) as seen in this Landsat-2 image. 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. Note the narrow strip of land (near image center) made up of marine deposits that encloses the Baia de Sepetiba.
This Landsat-7 ETM+ image shows much more detail within Rio de Janeiro:
This astronaut photo from STS61 Shuttle mission shows much the same area but with several landmarks labeled on the scene:
This city is the jewel of South America (although many who visit Buenos Aires would quibble with this statement).
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. Nearby, on another hill, is the hallmark of Rio, the statue of the Christ, with outstretched arms:
We have shown the inland pampas of Brazil as seen at Brasilia, the capital of Brazil built from "scratch" in the 1950s, on page 4-4. We repeat its coverage, using an astronaut photo from mission STS-38.:
A more detailed view of the central city is evident in this ALI (EO-1) view which includes the artificial lake and the Brasilia National Park (a savannah):
The government buildings in Brazilia are laid out in a broad expanse of open space:
Brazilia lies near the edge of the great drainage basin controlled by the Amazon River. Much of the basin is lowlands and is heavily forested but many of its rivers start on the eastern flank of the Andes and other areas of higher elevation. This map zeroes in on the main drainage elements of the Amazon Basin.
If one moves further north into the tropical forest of the Amazon basin, the denseness of the jungle where not clearcut is truly amazing (see page 3-5). Here is another aerial oblique photo of the Amazon as it flows through the eastern lowlands. Beneath it is an example of what usually comes first to one's mind when the Amazon jungle is mentioned.
Considering the vast density of jungle vegetation in the Amazon, it seems astounding that a major city of 1.2 million people has been carved out of the wilderness at the junction of the Amazon and Rio Negro Rivers. This is Manaus, shown in an astronaut photo.
The modernity of this expanding urban area is suggested in this aerial oblique view:
The sharp difference in the color of each river is brought out in this false color Landsat subscene; the blue marks strong reflectance in that spectral range by the great load of sediment in the ' Amazon:
The Amazon is one of the two longest rivers on Earth. It carries a tremendous load of sediment - largely contributed from the higher elevations in the basin. Three million tons of particulates are carried into the Atlantic Ocean each day. The mouth of the Amazon is some 380 km (207 miles) wide; note in the map of the basin above that the drainage area has actually constricted to a narrow zone on the east. Below are a Terra MISR image of the mouth region, with the sediment in brown, and a Landsat-1 image (fit it into the upper image) that shows just a part of the vast spread of sediment through the mouth. Much of the land around the mouth is actually part of the delta being constructed by the Amazon.
Before we leave the Amazon Basin and its rainforest, let's call attention to a sylvan variant, the cloudforest. This ecological biome refers to trees that form dense woods at elevations well above sealevel. The eastern tropical slopes of Ecuador support a cloudforest that transition into the rainforest. Rainfall is moderate to high but less than in the Basin interior. The cloudforest is the green area on the right in this Quickbird image:
Let's end our tour of South America by going to its southernmost point. Much of Chile and Argentina to the east that includes the Andes is called Patagonia. Here is an Envisat view of this region that makes up the southern fifth of South America:
The Andes continue to the tip of South America, a rugged region known as Tierra del Fuego. A Terra image of this region appears below. The scene is unusual in that it is mostly cloudfree; the passage of ocean cruise liners through the Straits of Magellan or around Cape Horn is always an adventure since the weather is capricious and the sea can be ferocious.
As you saw at the bottom of page 6-10, when we bundled Greenland with Canada, we again face an apparent non sequitur as to where to place the continent of the Antarctic during this world tour. This map illustrates the "problem".
Parts of Anarctica are closest to the Tierra del Fuego in South America, which you just saw above, and are about twice as far from southern Australia and South Africa. We will examine the Antarctic again on page 7-3 but for now there is this overview. First a mosaic of the continent, whose ice cap extends over about 13000000 square kilometers (geographic features of the Antarctic on imposed on another mosaic on page 7-3).
In the winter (during the summer in the northern hemisphere), sea ice forms an extensive shelf that greatly expands the Antarctic's size:
It is surprising to learn that there is really no one continuous rock continent below the ice cap comprising the Antarctic. Instead, its bedrock is a series of island archipelagoes that formed a base on which ice built up and extended from one island to its neighbors.
But now let's leave the western hemisphere to head east and cross the Atlantic Ocean to Europe.