In recent times, volcanic activity has greatly diminished over the continent and has ceased entirely in its eastern and north eastern section. Throughout the southern part of the continent there is evidence of several periods of glacial development and recession during the Ice Age. Ice covered the whole of the Pata gonian plateau as well as the western side of the Andes but the continental glaciation did not extend as far north on the east side of the Andes as on the west. Throughout the Andean zone there is evidence that the present glaciers are only remnants of much larger glaciers. There were no glaciers in the eastern or Brazilian section of the continent.
South America is the only one of the southern continents which extends far into the temperate latitudes; but, unlike the land masses of the northern hemisphere, it tapers toward the pole and, therefore, does not experience the extremes of temperature of the northern continents. The winters in the temperate latitudes are much warmer and the summers cooler than in North America or Asia. At no time of the year are there freezing temperatures at sea-level. The continent is broadest in the equatorial section and has the widest expanse of truly tropical weather of any of the continents ; but, because of the width of the zone covered by the Andes, it has also the greatest area of temperate and sub-Arctic climate in tropical latitudes. Off the west coast from Cape Horn to the Equator the isotherms bend sharply toward the north. North of 4o° S. lat. this is due to the cooling effect of the Hum boldt Current. The east coast as far as the La Plata estuary is washed by the warm south equatorial current which the projec tion of the continent at Cape San Roque divides into two branches. There it meets the cool waters of the Falkland Current flowing north from Cape Horn.
Except in the south the winds blow parallel to the Andes on the west coast. They bring heavy rainfall to Ecuador and Colombia. South of this section, however, to 3o° S. lat., the western side of the Andes and the coast are very dry on account of the Humboldt Current and the colder upwelling waters between it and the coast, and what little rain does fall there falls in the coolest months. South of 35° S. lat. there is much rain all the year but the maxi mum is in autumn and winter. This is the region of the Roaring Forties which in summer extend as far north as central Chile so that the Santiago region has mild rainy winters and rainless sum mers. In general the Andes offer a barrier to surface air circula
tion from both sides; but, south of 4o° S. lat. they are relatively low, and the west winds are able to cross them, their ascent bring ing heavy rainfall to the Chilean side while their descent causes the sparse rainfall of Patagonia. On the north coast of Colombia and the coasts of Venezuela and the Guianas the north-east trades blow all the year, strongest and steadiest in January and weakest during July when the rainy season occurs. The Equatorial zone has a double rainfall maximum from the north coast to about io° S. lat. ; but, except on the Equator, there is really one long rainy season with two especially heavy maxima. In all seasons the east coast, from Cape San Roque to the Tropic of Capricorn, has easterly winds varying from south-east in July to east and north east in January. Between the tropic and the La Plata estuary the coast is on the west side of the south Atlantic anticyclone all the year and has, therefore, warm rainy winds.
Discovery.—The continent of South America was first visited by Europeans in 1498 when Columbus, on his third voyage, touched near the mouth of the Orinoco. Others soon followed and by 1509 the east coast had been followed as far as the Rio de La Plata. In 1513 Balboa discovered the Pacific ocean at the Isthmus of Panama; in 152o Magellan navigated the strait that bears his name; in 1527 Pizarro landed on the coast of Peru at Tumbez, and, in the same year, Cabot ascended the La Plata and Parana rivers as far as the mouth of the Bermejo; in 1533 Cartagena was founded and the native town of Quito peacefully occupied; in 1535 Pizarro founded Lima and, in the same year Almagro invaded Chile and Mendoza established a settlement at Buenos Aires; in 1537 Jimenez de Quesada made his way from Santa Marta up the Magdalena river to Bogota, the capital of the Chibchas; and in 1541 Valdivia founded Santiago de Chile and Orellana travelled from eastern Ecuador to the Atlantic by the Napo and Amazon rivers. It is claimed that the bay of Rio de Janeiro was discovered by the Portuguese in 5502. Affonso de Souza visited it in 1531 but went on to Sao Vicente near Santos to establish his colony. The first settlement on the bay was made some years later by French Huguenots.