. THE GEYSER BASINS. 351 



llA'il'E.) 



rushing of the steam through the narrow orifices can be distinctly 

 heard bom the wag-on road. The mountain is one mass of altered 

 rhyolite, whitened by long action of steam and acid vapors. The 

 entire ridge, lying between the road and Solfatara creek to the east, is 

 largely formed of these highly altered rhyolites. It is evident that this 

 region was at one time a center of long continued and energetic ther- 

 mal activity. 



Beyond Twin Lakes the water drains southward to Gibbon river, and 

 from here to Norris basin along the roadside at the base of the cliff 

 there is a succession of steam vents, hot springs, and mud pots. 



NORRIS BASIN. 



This geyser basin (7,350 feet) occupies a depressed area on the east 

 side of the Gibbon river, the waters of the basin draining toward the 

 stream. Rhyolite ridges surround the basin, gradually rising on all 

 sides toward the summit of the plateau. In many respects this basin 

 la the most instructive of all, as the varied phenomena of thermal 

 act ion in all its phases are more clearly shown here than elsewhere. All 

 stages of rock decomposition and of deposition of sediments from hot 

 waters may be seen and are easily accessible to the pedestrian within 

 a short walk of the hotel. 



The basin contains 14 geysers, which, although neither so grand nor 

 impressive as those in the Lower and Upper Geyser basins, are, on 

 account of the varied phenomena exhibited, quite as interesting to the 

 geologist. Several of them are of quite recent origin, as is shown by 

 the freshness of the rocks through which the steam issues and by the 

 absence of sinter deposits. The Monarch is one of the most interesting 

 of the group. It breaks out through a narrow vertical fissure, 20 feet 

 long, in the rhyolite. Eruptions take place every four hours, the water 

 being thrown into the air for 50 feet. Other interesting geysers are the 

 Arsenic, Constant, Congress, Fearless, and Pearl. Owing to the great 

 number of steam vents and active orifices, each with some characteristic 

 feature of its own, the basin presents one of the most weird and desolate 

 regions in the Park. 



NOWKIS HASIN TO LOWER GEYSER BASIN. 



Shortly after leaving Norris basin the road crosses Gibbon meadows, 

 a broad open plain which in places is almost impassable owing to the 

 wet marshy nature of the bottom. The Gibbon river runs through 

 the Meadows. The ditches constructed for drainage purposes along 

 the roadside expose, underlying the meadow, a tine white earth several 

 feet in thickness, largely composed of diatoms developed in the sili- 

 ceous waters. Similar diatomaceous ooze is found in nearly all the 



