9. Climate. Rivers.

Map Questions.

1.Determine the distance of the northernmost and southernmost points of South America from the Equator.

2.What season is it now in the southernmost part of South America?

3.Name a large South American river that you have heard of.

Climate. The greater part of South America on both sides of the Equator lies in the torrid zone. The Equator crosses South America in the north and not, as it does Africa, in the centre. A large part of the continent in the south extends beyond the Tropic of Capricorn and lies in the temperate zone. Therefore South America, on the whole, is not so hot a continent as Africa.

If you examine the climate map, you will see that the January temperature almost everywhere in South America is over 20°C above zero. Only in the far south and in the mountains does it drop to 10oC.

Tropical South America on both sides of the Equator is influenced by the trade winds blowing from the Atlantic.These winds bring heavy rain to both the north-eastern and south-eastern coastal regions and to the Amazon Lowlands. In the equatorial belt the heated currents of air rise, and upon being cooled, cause heavy rains in this region.

In the southern part of South America lying in the temperate zone westerly winds blow from the Pacific. For this reason the west coast receives much rain. The east coast, on the other hand, is sheltered from the moist westerly winds by the Andes and is, therefore, dry.

Several contrasting climatic regions may be distinguished in South America

In the torrid zone lie the Amazon Lowlands. This is a wet equatorial region. On either side, north and south, lie regions where winters are dry and where rain falls mostly in summer. Westwards, along the Pacific coast, lies a dry desert region, extending from latitude 5° to 30° S. Further south lie two subtropical regions, with wet summers on the east coast and the La Plata Lowlands and dry summers on the west coast. The southernmost part of the continent lies in the temperate zone. Here the region lying to the east has a desert climate, the one to the west on the Pacific coast, a wet maritime climate. The Andes have an Alpine climate which changes with the altitude and is, therefore, very varied.

Rivers. Most of the large rivers of South America flow into the Atlantic. Owing to the wet climate South American rivers contain very muchwater. As they flow down the ledges of the Brazilian Highlands, many of them form great waterfalls and rapids that hinder navigation. The enormous supplies of water-power are almost unused.

South America's greatest river is the Amazon. It ranks third in the world in length (6,480 kilometres together with its tributary the Ukayali). In size of basin (over 7,000,000 square kilometres) and volume it ranks first. The Amazon rises in the Andes near the Pacific. After cutting through deep gorges it flows across the wet Amazon Lowlands. Here it is joined by its chief tributaries, some coming from the north, others from the south. In its middle course its width is 5 kilometres and its depth 70 metres. In its lower course it reaches a width of over 20 kilometres and a depth of 100 metres. It divides into several channels in places. Its northern and southern tributaries flood at different periods, depending on the rain. The Amazon, therefore, is high-watered throughout the year, though its level is higher after the floods of the larger southern tributaries. In such cases it overflows its banks and floods enormous areas. Upon falling into the Atlantic it forms a great bay with numerous shoals and islands. The tidal waters penetrate far upstream. They cause high waves that tear along with a great noise, flooding the banks of the river. The Amazon is navigable its entire length, from the Atlantic to the Andes.

The second largest and deepest river is the Parana. It rises in the Brazilian Highlands, from where it flows across the La Piata Lowlands into the Atlantic. Its wide estuary is called the R i о d e la Plata.

Across the north of the continent flows the Orinoco, forming a large delta at its estuary.

There are many Alpine lakes in the Andes.

Questions and Assignments.

1.Study the climate map and explain why the western shores of South America at latitude 20°S receive little rain and the eastern much, while at latitude 45°S. on the contrary, the western shores receive much rain, the eastern little.

2.Compare the Amazon and Nile as to geographical position, length, size of basin, volume, etc. Account for the great volume of the Amazon.

3. Mark the names of the South American rivers on the outline map.

NATURAL ZONES.