FOSSIL FOEESTS OF YELLOWSTONE PARK. 



7 



Kange of mountains, in Park and Gallatin Counties, Mont. This 

 forest, which lies jnst outside the boundary of the Yellowstone 

 National Park, is said to cover 35,000 acres and to contain some 

 wonderfully well preserved upright trunks, many of them very 

 large, equaling or perhaps even surpassing in size some of those 

 within the limits of the park. Two of the best preserved of these 

 trunks are shown in figures 2 and 3, which are here reproduced by 

 the kindness of Mr. E. C. Alderson, of Bozeman, Mont. 



In the beds of the streams and gulches coming down into the 

 Lamar River from Specimen Ridge and the fossil forests one may 

 observe numerous pieces of fossil wood, which may be traced for a 

 long distance down the Lamar and Yellowstone Rivers. The farther 

 these pieces of wood have been transported downstream, the more 

 they have been worn and rounded, until ultimately they become 

 smooth, rounded " pebbles " of the stream bed. The pieces of wood 

 become more numerous and fresher in appearance upstream toward 

 the bluffs, until at the foot of the cliffs in some places there are hun- 

 dreds, perhaps thousands of tons that have but recently fallen from 

 the walls above. One traversing the valley of the Lamar River may 

 see at many places numerous upright fossil trunks in the faces of 

 nearly vertical walls. These trunks are not all at a particular level 

 but occur at irregular heights; in fact a section cut down through 

 these 2,000 feet of beds would disclose a succession of fossil forests 

 (see fig. 4). That is to say, after the first forest grew and was 

 entombed, there was a time without volcanic outburst — a period long 

 enough to permit a second forest to grow above the first. This in 

 turn was covered by volcanic material and preserved, to be followed 

 again by a period of quiet, and these more or less regular alternations 

 of volcanism and forest growth continued throughout the time the 

 beds were in process of formation. 



GEOLOGIC RELATIONS. 



While these fossil forests were growing and being entombed, much 

 of the area now within the limits of the park, as well as large adja- 

 cent areas, was the scene of tremendous geologic activities. After the 

 Cretaceous period (see diagram p. 30), there was a time of great 

 volcanic activity, which appears to have lasted until perhaps the be- 

 ginning of the glacial epoch. There were many active volcanoes just 

 east, north, and w^est of the park, and some in the park itself. From 

 these volcanoes vast quantities of material were poured out, building 

 up in places Avhole mountain ranges. Thus the major portion of the 

 great Absaroka Range, just east of the park, as it appears to-day, 

 was built up of volcanic material. 



