QUATERNARY AGE. 291 



CHAPTER IX. 



QUATERNARY AGE AND SUPERFICIAL DEPOSITS, 

 CONTINUED. TERRACE EPOCH. ALLUVIUM. 

 SAND HILLS. ALKALI LANDS. TIMBER, AND 

 CAUSE OF CHANGES OF CLIMATE. 



Relationship of the Terrace Epoch to Subsequent Times. Level of the 

 Land. Gradual Formation of Terraces. Highest Elevation Reached, and 

 its Effects in the West. Section Showing Glacial Action. Effect of Ex- 

 treme Elevation on River Channels. Varying Heights of Terraces. Allu- 

 vium. Its importance, and How Gradually Produced. Character of the 

 Bottom Lands, and their Great Extent. Analysis of Alluvium. Sand Hills, 

 and their Extent and Geological Character. Theories about their Origin. 

 Pliocene Origin of Many of Them. Capabilities for Cultivation. Alkali 

 Lands. Extent and Character. Analysis of Alkali Soils. How to Cultivate 

 Them. Hard-pan, or "Gumbo" Soils. Their Character, Extent and Analysis. 

 Bad Lands. Their Superficial Character and Appearance. Organic Re- 

 mains, and Agricultural Character Fuel from the Surface Deposits. Peat. 

 Its Extent and Character. Timber in Modern Geological Times. Causes 

 of Changes of Climate. 



F 



TERRACE EPOCH. 



HROM the preceding, it ic evident that the Terrace Epoch in 

 Nebraska is closely connected with that order of events and 

 with tho<e changes that finally resulted in the present order of 

 things. It commenced here after the close of the Loess period. 

 When the rivers covered the whole of the existing bottoms, and 

 had the old Loess lake bed for a flood -plain, the land still lay far 

 below its present level, and was in the transition stage between the 

 Loess and Terrace periods. When the elevation became a little 

 greater, and the drainage better, and the volume of water less, it 

 cut a new channel amid its old bed, which now constituted its 

 flood-plain. This formed the first terrace, and fully inaugurated 

 this epoch. Here the land and the river must have stood for ages. 

 Again there was an upward movement, the drainage became still 

 better, the volume of water lessened, and another channel formed, 

 and the previous river bed changed to a flood-plain. Thus terrace 



