
The SciencesDecember 1, 1952
Arroyos
A century ago the valleys of the Southwest were green; now they are brown and cut by gullies. Man is blamed for the change, but he has only added a factor to the geologic cycle that causes it

Arroyos
A century ago the valleys of the Southwest were green; now they are brown and cut by gullies. Man is blamed for the change, but he has only added a factor to the geologic cycle that causes it