THE LANDSCAPE AND ITS ATTRIBUTES
Other drainage adjustments
Many other streams in the Uinta Mountains have had their courses drastically altered during the past few million years. Particularly at the flanks of the range, drainage became channeled into courses controlled by alternately hard and soft strata. In such areas, as downcutting progressed in belts of tilted rock, streams eroding across resistant ledges tended to yield to streams that flowed along softer strata. Much like a board left to weather in the elements, the harder layers were etched into relief, the softer ones were hollowed out.
Drainage of this sort, said to be structurally adjusted, is clearly visible in the Flaming Gorge area, where several ancestral drainage lines are indicated by abandoned wind gaps. Dutch John Gap is an excellent example (fig. 33); Irish Canyon, at the east end of Cold Spring Mountain, is another (Sears, 1924). Dutch John Gap once channeled the drainage that now flows down Spring Creek; Irish Canyon may once have contained Vermilion Creek.
On the south slope of the range, the hogbacks and racetrack valleys that encircle Split Mountain and that flank Blue Mountain are fine examples of structurally adjusted drainage lines. Although the master streams of these areas, the Green and Yampa Rivers, were able to ignore geologic structure, many of their less competent tributaries were forced into courses adjusted to rock hardness. Many of these tributaries, in fact, are so well adjusted to the structure of the underlying bedrock that the trained eye can discern the structural form from the drainage pattern alone.
Weber, Provo, and Bear Rivers
Notable stream adjustments at the west end of the Uinta Mountains are clearly shown on the old (1900) Coalville quadrangle map and are reproduced in figure 34. At one time the Weber River, which flows to Great Salt Lake, quite apparently drained all the western part of the range, including areas now drained by the Provo, which flows to Utah Lake. The Provo River has greatly expanded its drainage basin and, hence, its discharge, at the expense of the Weber. The Upper Provo once flowed north through Rhodes Valley into the Weber. It was diverted into the present Provo River, however, when it was captured at a point about 2 miles south of the town of Kamas.
There, the present river leaves a wide, flat-bottomed valley and enters a narrow canyon en route to Heber Valley and, ultimately, Utah Lake. Its diversion was aided, perhaps, by the clogging of Rhodes Valley with late glacial outwash. Hence, the diversion probably was a geologically recent event.
Other adjustments on the Provo have occurred farther upstream. The headwaters of the present river once flowed into Beaver Creek, a tributary of the Weber, but they were beheaded by a tributary of the ancestral Provo that eroded northeastward through Pine Valley. A broad low saddle marks the site, and many motorists today pass this point on Utah State Highway 150 with out realizing that they have crossed from one drainage basin to another and that waters on opposite sides of the saddle flow to outlets 65 miles apart.
Although the Weber River has thus lost nearly half its flow to the Provo, it has gained flow from the Bear in drainage adjustments that are not really momentous, perhaps, but that are important to the drainage budgets of the streams involved. Chalk Creek, a major tributary of the Weber, arises in the northwestern Uinta Mountains (fig. 35). The headwaters of Chalk Creek flow north and northwest, enter Wyoming, and then turn abruptly south and southwest, back into Utah toward the Weber. Chalk Creek's north-flowing reach is separated from the Bear River by a low divide, but its southwest reach passes through deep canyons en route to the Weber. In all probability the headwaters of Chalk Creek formerly drained into the Bear, either directly or via Yellow Creek, but they were diverted southwestward by headward erosion of lower Chalk Creek, and the point of diversion was the "elbow" in its course at the Wyoming State line. Between that point and Pine Cliff, the direction of flow has probably been reversed. Notice (fig. 35) how the tributaries upstream from Pine Cliff are "barbed"they flow in the opposite direction from Chalk Creek itself.
The Weber has also captured drainage from the West Fork of the Bear (fig. 36). A relatively minor but illustrative stream diversion north of Holiday Park characterizes a type of capture that has happened time and again elsewhere in the Uinta Mountains. Near Holiday Park, the Weber Valley is 1,200-1,500 feet lower than the West Fork of the Bear just across the divide. With much steeper gradients, the headwaters of the Weber, therefore, have a distinct hydraulic advantage over the headwaters of the West Fork. Larrabee Creek, a small steep tributary of the Weber, has eroded headward to the north, has thus intercepted the east flowing drainage of Windy Peak, and has diverted it south from the Bear to the Weber drainage. This drainage capture was a minor physiographic event, but in a small way it typifies the ever-changing, ever-evolving sequence of events begun eons ago that culminated, from man's point of view, in the dramatic landscape of the present Uinta Mountains.
Rock Creek and the Duchesne River
Old drainage adjustments are probable between the headwaters of the Duchesne River and Rock Creek. The Duchesne River drains a well-watered area, south of the crest of the range, centered between Bald Mountain and Mount Agassiz. Drainage from this area probably flowed at one time into Rock Creek by way of the West Fork of Rock Creek (fig. 37). The evidence of capture by the Duchesne still looks convincing on topographic maps, especially on the raised relief edition of the Salt Lake City map (4 miles per inch) and on the old Hayden Peak quadrangle map (2 miles per inch), despite intensive glacial scouring since the postulated diversion. Early glaciation may even have contributed to capture by abrasively reducing the height of the intervening divide. At present, the upper Duchesne is deeply entrenched in a youthful canyon, whereas the West Fork of Rock Creek heads in a broad wind gap perched above the Duchesne and open in that direction. The difference in altitude between the wind gap and the Duchesne River below is nearly 800 feet.
Glacial diversions on the north flank
Glaciers commonly obstruct and divert preglacial drainage lines, either by blocking them directly with ice or, on melting, by obstructing them with morainal debris. Good examples of such diversions can be seen on the north flank of the Uinta Mountains in tributaries of Beaver Creek and Burnt Fork. Diversions by glaciers of the last major advance (Pinedale) are particularly evident. The Middle Fork of Beaver Creek, for example, probably once flowed directly north into the West Fork, as shown in figure 38, but it has since been diverted eastward into its present course by massive lateral moraines left across its course by the last glacier to occupy its valley. Note also how Fellow Creek was shouldered aside by Pinedale moraines and how a tributary of Henrys Fork was diverted into Fellow Creek (fig. 38).
Hoop Lake and Lost Creek are other examples shown in figure 38. Preglacial drainage of the Hoop Lake basin was east into Burnt Fork, but it was obstructed by moraines of the former Burnt Fork glacier. The resulting depression was filled with waterthus forming Hoop Lakeand drainage from Hoop Lake spilled over into the East Fork of Beaver Creek. (Hoop Lake is a natural water body, although its level has been raised by a dam.)
Lost Creek no doubt once flowed unhindered into Burnt Fork, but its course, too, was blocked by a large moraine of the Burnt Fork glacier. Lost Creek then found an outlet in a solution cavern in the Mississippian limestone. Where the water goes from there has long been a matter of cracker-barrel speculation among old-time residents. Some guess that it emerges 15 miles to the east in Sheep Creek Canyon, where large springs issue from the Mississippian at Palisade Park. Perhaps they are right. Reportedly, roily discharge from the springs sometimes follows shower activity over the Lost Creek watershed.
Last Updated: 18-Jan-2007