Chapter 20 homework

Chapter 20, Section 1

1. The Great Rift Valley, stretching from Syria in Southwest Asia to Mozambique in the southeastern part of Africa, has been formed by the shifting of tectonic plates. In East Africa, the Great Rift Valley forms two branches, with volcanic mountains rising at its edges and deep lakes that run parallel to its length.

2. Lakes and rivers are located in huge basins formed millions of years ago by the uplifting of land. The great rivers of Africa originate high in the plateaus and eventually make their way to the sea. Escarpments and ridges break the rivers’ paths to the ocean with rapids and cataracts. The broken landscape makes it impossible to navigate most of the region’s rivers from mouth to source.

Creative Writing:
Rainfall is irregular and unpredictable, making it difficult to control water for practical uses such as irrigation and hydroelectric power. Lake Chad, outside the Great Rift Valley, in west-central Africa is threatened with extinction. Factors contributing to the shrinkage of Lake Chad include global warming, irrigation and desertification. As the lake shrinks, the desert expands on the dry lake bottom which reduces the amount of fertile soil where mineral resources could be found.

Chapter 20, Section 2

1. In addition to rainfall other factors such as ocean currents, prevailing wind patterns, elevation, and latitude often cause great variations in climate and vegetation. Dueling winds affect the tropical dry climate of western Africa. Hot, dry air streams in from the Sahara on a northeast trade wind known as a harmattan that dries up moisture left by heavy summer rains.

2. Tropical Wet, Tropical Dry, Steppe, Desert, and Midlatitude Climates are found in Africa south of the Sahara. These climates consist of shrubs, ferns, mosses, trees, palms, orchids, low-growing grasses, and acacia trees.

Creative Writing:
The Serengeti Plain is one of the world’s largest savanna plains. It has a tropical dry climate with alternating dry and wet seasons. It is home to millions of animals such as zebras, gazelles, hyenas, lions, giraffes, and cheetahs. The vegetation consists of scattered trees and tall grasses. The soils are not very fertile. The Great Pains in the United States has a humid continental climate and benefits from warm, moist winds that blow north along the Rockies from the Gulf of Mexico and cold, moist winds that blow south from the Arctic.