The third beach.
The failing water.
Then once more the waters went down, down, down. Step by step they receded until the secondary beach was left a hundred feet above the water level. Again there was a pause. Again new beaches were beaten into shape by the waves, new bays were opened, new arroyos cut through from above. The whole process of shore-making—the fitting of the land to the shrunken proportions of the lake—was gone through with for the third time; while the water supply from the river or elsewhere was maintained in decreased volume but with some steadiness of flow. Possibly the third halt of the receding water was not for a great length of time. The tertiary beach is not so large as its predecessors. There never was any strong wave-action upon it, its pebbles are few, its faults and breaks are many. The water supply was failing, and finally it ceased altogether.
Evaporation.
What fate for a lake in the desert receiving no supplies from river or sea—what fate save annihilation? The hot breath of the wind blew across the cramped water and whipped its surface into little waves; and as each tiny point of spray rose on the crest and was lifted into the air the fiery sunbeam caught it, and in a twinkling had evaporated and carried it upward. Day by day this process went on over the whole surface until there was no more sea. The hollow reefs rose high and dark above the bed, the flat shoals of silt lifted out of the ooze, and down in the lowest pools there was the rush and plunge of monster tortuabas, sharks and porpoises, caught as it were in a net and vainly struggling to get out. How strange must have seemed that landscape when the low ridges were shining with the slime of the sea, when the beds were strewn with algæ, sponges, and coral, and the shores were whitening with salt! How strange, indeed, must have been the first sight of the Bottom of the Bowl!
Bottom of the Bowl.
Drying out of the sea-bed.
Advance of desert.
But the sun never relaxed its fierce heat nor the wind its hot breath. They scorched and burned the silt of the sea-bed until it baked and cracked into blocks. Then began the wear of the winds upon the broken edges until the blocks were reduced to dry fine powder. Finally the desert came in. Drifts upon drifts of sand blown through the valleys settled in the empty basin; gravel and bowlder-wash came down from the mountains; the grease wood, the salt-bush, and the so-called pepper-grass sprang up in isolated spots. Slowly the desert fastened itself upon the basin. Its heat became too intense to allow the falling rain to reach the earth, its surface was too salt and alkaline to allow of much vegetation, it could support neither animal nor bird life; it became more deserted than the desert itself.
Below sea-level.