Page:History of Iowa From the Earliest Times to the Beginning of the Twentieth Century Volume 1.djvu/38



portions of the land; birds appear in the woods and a few small rat-like animals are found, as well as reptiles.

But another great change comes; the waters again cover the northwestern portion of the State and ages come and go before the sea recedes, never to return. Iowa has finally been raised above the sea level and the waters drain toward the ocean, forming great rivers, and plowing deep channels through the oozing sediment. The sun and wind finally dry the surface; forests and rank vegetation again make their appearance; animals come forth from Nature's nurseries and spread themselves over the land, and roam through the jungles, preying upon each other in their struggle for food. The climate is that of the tropics, and myriads of forms of life are evolved.

All of the conditions are now favorable for the advent of man, but no evidence is found of his existence on any portion of the earth at this period. The rivers, which ages later were named the Mississippi and Missouri, were then carrying the inland waters to the sea which reached as far north as the Ohio river.

Where the upper Missouri now flows through the prairies of Nebraska, the Dakotas and Montana, where lakes spreading over a large portion of these States. Remains of forests and strange species of animals, long since extinct, have been found in the sediment that was formed in these lakes. Tropical trees such as the cypress, magnolia, cinnamon, fig and palm flourished in Iowa, Dakota, and far northward into British America; tropical birds sang in the forests; huge reptiles crawled about in the rank vegetation and swamps.

Then came the Tertiary period. Iowa was a part of the land area which then made up the half formed continent of North America. The drainage of the State must have been much the same as now, although the altitude above sea level was several hundred feet lower.

In the beds of Tertiary lakes were entombed animals and plant remains which man in these late generations has