Three illustrations showing the crumpling and wearing of the earth over geologic time. At top can be seen the great crumples and folds in the early crust of the earth, with molten igneous rock forced into them, and in one place bursting through. The middle illustration shows the folds many years later when rain, rivers, frost and wind have greatly worn them down. The bottom image shows folds in modern times still more worn down, showing valleys, hills, sea and soil.