REDROCK LAKE NEAR WARD, COLORADO 1 

 I. Topography and Geology 



Location. — Redrock Lake is located in Boulder County, Colorado, 

 about 2\ miles (4 kilometers) west of Ward, in the drainage of the 

 South St. Vrain Creek, longitude 105 30' W., latitude 40 05' N. It 

 has an altitude of 10,100 feet (3,080 meters). The continental divide 

 is about 3 miles (5 kilometers) west of the lake, this distance being 

 much less than that of most localities at the same altitude. 



Glaciation. — During Pleistocene times many parts of the mountains 

 of Colorado were glaciated. In the region studied glaciation is very 

 evident. The glacier extended to some distance east of Redrock Lake 

 and down to an altitude of about 9,300 feet (2,843 meters). Glacial 

 action and subsequent erosion have formed a topography consisting 

 in general of a series of morainal ridges running parallel with and at 

 various angles across the longitudinal axis of the valley. Redrock 

 Lake lies in a depression between such morainal ridges. 



Boundaries. — On the lower side of the lake is a morainal ridge about 

 9 meters (30 feet) high. This ridge swings around and connects with 

 one on the south of the lake about 23 meters (75 feet) high, and one on 

 the north about 3 meters (10 feet) high. To the west is a low ridge 

 separating the lake from a wet meadow. The E-W and N-S cross 

 profiles (see Figs. 2 and 3) of the lake give the relative steepness 



1 Colorado, with its mountains and plains, offers exceptional opportunities for the study of lake and 

 streamside vegetation. Lakes are abundant on the plains and in all the mountain zones, up to and including 

 the alpine zone. The streamside vegetation of a single stream may be studied with profit by following it from 

 ts head, in alpine regions, through the sub-alpine, montane, foothill and finally into the plains zone. In the 

 study of the lake and streamside vegetation of a mountainous region it is possible to make valuable comparisons 

 of species peculiar to certain habitats as influenced by climatic conditions. Edaphic and climatic factors, in 

 their various relations to each other, can be studied with much satisfaction. 



The present study, the first of a series, is concerned with the vegetation of a single lake which is typical 

 of the sub-alpine region. The writers have under observation and have collections from about twenty-five 

 akes and ponds at various places in Colorado. These lakes range in altitude from 5,000 to 12,000 feet (1,530- 

 3,660 meters). The intention is to make comparisons of the vegetation in and about these lakes and also 

 with that of lakes studied by others. Various ecological stages and different geologic types are represented; 

 thus conditions are favorable for the study of the relations of the plant formational changes to the physiographic 

 changes and the interact-'on of different plant associations upon each other. 



Collections and studies of streamside vegetation have been carried on the past season. This work will 

 be continued from year to year in connection with the study of lakes. 



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