This province is so dearly defined in most respects that it is 

 widely recognized as forming a unit within the otherwise 

 complex terrain of the West and has acquired a popular name— 

 the Great Basin. It is not strictly a basin, either geologically or 

 in structure, for it does not slope inward from its subcircular 

 periphery but is nearly level, though its surface is covered with 

 ranks of mountain chains. It is almost entirely ringed by steep, 

 high mountain walls. It can be divided into three not too well 

 defined subregions, and has an appendage to the north — an 

 area commonly called the Guttered Scablands. 



Its boundaries are formed on the east by the Utah block of 

 the South Montane and a portion of the North Montane 



provinces: on the north by the southern face of the North 

 Montane Block plus the Blue Mountains, which lie entirely 

 zvithin its confines; and on the west by the barrier of the 

 Cascades to the northwest and the Sierra Nevada to the 

 southwest. Its southern boundary appears to be arbitrary on a 

 map but may be outlined by the zone of change from the red 

 soils of the Sonoran Deserts of the south to the gray soils of the 

 Scrub Belt of the north. The Great Basin as thus defined is 

 some eight hundred miles long from north to south and five 

 hundred in width. It is shaped like a human heart. 



This is an odd province in many respects. First, it is 

 geologically rather new as a physiographic unit and is stilt 

 changing somewhat rapidly. Second, unlike all other provinces 

 on this continent, its nature and appearance, although still 

 basically dependent upon its position among the major 

 vegetational belts, is much influenced by secondary forces. 

 Prominent among these is absence of rainfall, due to mechanical 

 factors — namely, the almost complete atmospheric moisture 

 trap formed by the Cascade— Sierra Nevada barrier to the west, 

 which cuts off the prevailing moisture-laden winds from the 

 Pacific. Third, it has no indigenous drainage system apart from 

 the Snake River in the far north, which today merely carries the 

 runoff from the Northern Montane Block through its territory. 

 The Scablands form a distinct subprovince. 



The body of the area is hilly, but the northwest forms a 

 level and rather featureless platter, whereas the northeast 

 portion, comprising the Snake River valley, is a wide, almost 

 flat gutter. The remainder of the province, south of the 

 forty-second parallel, is roughly triangular, is lined with 

 north-to-south parallel strings of small mountain ranges, and 

 drops to large depressions on either side. These were once the 

 sites of the huge lakes today named Lahontan, on the west, and 

 Bonneville, on the east. This subprovince is excessively arid and 

 may be included in the Desert Belt. For a further note on the 

 limits of desert belts, see "An Explanation and Glossary." 



that occupy a central position in the belt between the Prairies 

 and the Savannahs. Just where they begin and end in relation- 

 ship to the Scrub Belts is definable only by changes in the facies 

 of the flora and fauna. 



WHERE ARE OUR DESERTS? 



This question is almost as troublesome as the preceding one. 

 Deserts were unknown to the first English settlers. Then it was 

 learned that the lands of the Spaniards in the Southwest were 

 called by their colonizers desiertos, and it was immediately 

 concluded that most of Mexico and the southern "West" were 

 covered with waterless and completely unvegetated seas of sand. 

 However, after the Louisiana Purchase and the beginning of the 

 drive to the West, a reaction to this set in. Early travelers 

 reported, quite legitimately, that many places which were sup- 

 posed to be covered with "deserts" were not only fertile but 

 even supported considerable forests. 



The government deliberately fostered these tales, in order to 

 encourage mass immigration in the shortest time possible. The 

 famous Major Powell, the first scientific explorer and surveyor 

 of the Southwest and the founder of the United States Geological 

 Survey, fought this propaganda for half a lifetime and lost. Not 



until after his death did the truth of what he had so stead- 

 fastly contended became obvious — namely, that the South- 

 west could not be made to produce even low-grade meat and 

 vegetables unless something substantial was done to augment 

 its rainfall of less than ten inches a year. Its "desert" reputation 

 was consequently revived. 



The next phase came when the Southwest had been populated 

 and roughly surveyed, and scientific investigation and precision 

 became general practice. The deserts then began to shrink again 

 — in time almost to the point of disappearance — so that state- 

 ments may be found in official literature to the effect that, at 

 least technically, there are no real deserts in the United States 

 or even in North America. This seems to be in part a reversion 

 to the old north European idea of a desert as a sandy waste — 

 coupled, I would suggest, with a misconception of the Scrub 

 Belts or a simple failure to recognize that these exist. 



Nonetheless, there are vast arid areas on this continent, either 

 with scant vegetation or with none at all, which are commonly 

 referred to as deserts and which by proper scientific definition 



The sand dunes of upper Death Valley are unique: they 

 not only come in many colors but often are banded or 

 neatly striped, their grains being sorted by the wind. 



232 



