THE COLUMBIA BASIN AND THE GREAT BASIN 128. Rich volcanic soil.— A farmer in the state of Washington had a thou sand acre wheatfield on which he grew, in one year, forty-six thousand bushels of wheat. This is a very large yield indeed. The average yield of wheat in the United States is only about one-third as much per acre. Still more won derful to relate, this field had been in wheat for thirty one successive years. The farmer of Indiana or other eastern wheat growing states never thinks of raising wheat for more than two or three years on the same ground, because the crop becomes poor, and the land must be given a rest by growing some other crop. Why do the Washington wheatfields yield so much? Two strange words give the answer: volcano and lava. Once upon a time great volcanoes poured out floods of melted rock, called lava, that flowed like water, and covered nearly 200,000 square miles of land in the Columbia Basin and the Great Basin. How do men know this? Some river canyons help to tell us. Examine Fig. 134.
129. The Snake River canyon.—This river, like many other streams in this basin, has cut through the lava a narrow, deep valley, or canyon (Fig. 142). The Snake River canyon is several hundred miles long, three to four thousand feet deep. In the wall of that can yon one can see layer after layer of lava rock of various colors, sometimes with the upper edge of one flow turned into a layer of soil and then buried by the next flow (Fig.
134). At the bottom, is the surface of the old land surface that was buried by lava.
130. Why lava soils are rich.—The lava has been on the surface long enough to decay and turn into a deep soil, so very rich that it makes the Washington wheat-fields yield more per acre than those of any other wheat region in America. Why is lava soil so
rich? Because it is new. Most soils are second-hand soils, third-hand soils, or even older than that. Think for a moment of the sands of Florida. They were washed down there when Florida was sea bottom. The geologists will tell you that the rocks in Georgia, from which some of the Florida sand was washed, were made of material washed there from some other place. Soil may have been moved in this way many times. All this washing soaks out some of the plant food, and leaves many of the old soils poor. But the lava is fresh, new stuff out of the crust of the earth, and is rich in plant food. This lava soil covers about 200,000 square miles of the surface of the wide upland region lying between the Rocky Mountain System and the Pacific Mountains.
131. Bounds and climate.—Name four mountain ranges that bound this region. The northern part, drained by the Columbia River, is called the Columbia Basin. The southern part, with no stream reaching the sea, is called the Great Basin. (Map, Fig. 91.) Because of its fertile soil the people of the Columbia Basin like to call their region " The Inland Empire." The Basin region has a healthful climate, which is much milder than that of the Great Plains on the eastern side of the Rockies, because the prevailing winds are warmed by the waters of the Pacific Ocean. There is but little snow in winter, and while the summer sun is hot, the nights are cool. If it only had enough rainfall everywhere for good agriculture, the Basin region would be a better agricultural country than France or Germany.