NORTH AMERICA. Relief. Minerals.

Map   Questions.

Relief. As compared to Europe and Asia, North America's relief is not so complicated. It is more varied, however, than Africa's.
If you study the map of North America, you will notice a distinct contrast between the elevated western part of the continent and the lower eastern part (Fig. 152).
Along the western coast, from Alaska to the Isthmus of Panama, extend the Cordilleras. This young mountain system was formed at about the same time as the Alps and Himalayas and is very high. Its peaks reach an altitude of 5—6 thousand metres and are second only to the loftiest peaks of Asia and South America.
In the north the Cordilleras are covered with perennial snow. Powerful glaciers move slowly down the slopes to the valleys where they melt, forming wide streams that reach the sea in places. The lofty peaks in the south are also covered with perennial snow.

Fig. 152. North America: Relief and minerals.

The Cordilleras consist of several ranges, some extending along the coast, others further inland.
The series of plateaus and uplands lying between these ranges include the Great Basin in the central part of North America and the Mexican Plateau in the southern part. Mountains are still in the process of formation in the Cordilleras, as the frequency of earthquakes in this region shows. So violent are some of the shocks that entire towns and villages are destroyed.
There is still considerable volcanic activity in the neighbourhood of the Cordilleras. Active volcanoes exist both in the north and south. Large areas are covered with hardened lava. Extinct volcanoes are numerous. Powerful geysers throw up fountains of hot water and steam at regular intervals. Majestic volcanoes raise their cones high above the Mexican Plateau. In the course of the last two hundred years two new volcanoes appeared here. They poured out lava, ejected a great deal of ash, built their cones and then calmed down.

Together with the volcanoes on the eastern coast of Asia and islands of the Pacific Ocean, the volcanoes of America form a ring encircling that ocean.
Parallel to the eastern coast of North America southward of Labrador run the Appalachian Mountains. Unlike the Cordilleras, they are the remains of ancient mountains. Much denuded and worn down, they do not rise above 2,000 metres (Fig. 153).
The entire area between the Cordilleras and Appalachians is flat country that sinks to the north and south, forming lowlands

Fig. 153. An Appalachian Mountain scene. A valley amidst the sloping hills.

along the coasts of the Arctic Ocean and Gulf of Mexico. The one to the south is drained by the Mississippi and is, therefore, called the Mississippi Lowland. It consists mainly of silt brought down by that great river. The Mississippi Lowland merges into that bordering on the Atlantic Ocean east of the Appalachians.
Minerals. North America is rich in minerals. There are large de­posits of iron ore in the ancient Appalachian Mountains and enormous deposits of coal along their western slopes. Rich deposits of iron ore as well as nickel are found in the districts- round the Great Lakes and on the island of Cuba.
The Cordilleras are rich in gold and copper, uranium and poll/me­tallic ores.
There are large deposits of oil and gas north of the Gulf of Mexico and on the Pacific coast north of the peninsula of California.
Questions and Assignments.