Smith Geo 246b
Geology of Death Valley
A 5-College Field Trip to Death Valley
Leaving March 13 - Return March 21
Class Meetings: Thursday Evenings at 7:30 p.m.
McConnell Hall B15, Smith College
Faculty
STUDENT REPORTS
Landsat Image of Death Valley
Geologic cross-section of Death Valley
An alluvial fan is a stream deposit whose surface forms a segment of a cone that radiates downslope from the point (apex) where the stream channel emerges from a mountainous area (Bull, 1964). Stream channels on fans are commonly braided with a distributary pattern. Fans range in size from several hundred meters to tens of kilometers in radii. The largest fans occur where erosion dominates in the moutainous areas and rivers transport the eroded sediment to an adjacent basin. Fans may coalesce to form an alluvial apron called a bajada. The longitudinal profile of most fans appears to be concave upward as gradients near the toe of the fan are 3-6 degrees and steepen to near 10 degrees at the apex. Bull (1977) noted that radial profiles of fans in the Central Valley of California actually were made up of a series of straight line segments. He suggested three hypotheses to account for this:
- Climatic Change
- Tectonic Activity
- Base Level Change
Fans have been classified into two basic types by Schumm (1977). Dry fans are those created under ephemeral flow conditions in arid regions while Wet fans are formed by perrenial streams.
A fan in Death Valley. Note incised apex.
Although alluvial fans are a dominant feature in arid climates, they occur under virtually all climate conditions.
Cedar Creek alluvial fan near Ennis Montana.
Images of Death Valley Alluvial Fans
Evaporite formation on the playa
Moving rocks on Racetrack Playa
Sand dunes at Death Valley
The Ubehebe crater.
Collected During the Trip
| SAMPLE SITE | SPEC COND | CHLORIDE | SULFATE | NITRATE |
| Eagle Borax Spring | 7,200 micromhos | 870 mg/L | 2,700 mg/L | 8 mg/L |
| Tule Spring | 3,170 | 980 | 150 | 1.5 |
| Badwater | 62,400 | 27,000 | 5,720 | 200 |
| Salt Creek | 25,900 | 9,300 | 3,800 |
Analyses courtesy of Smith aqueous geochemistry class.
| SAMPLE SITE | Na | K | Ca | Mg |
| Eagle Borax Spring | 1,180 mg/L | 120 mg/L | 410 mg/L | 174 mg/L |
| Tule Spring | 439 | 10 | 100 | 69 |
| Badwater | 16,500 | 726 | 1,825 | 200 |
| Salt Creek | 6,270 | 560 | 260 | 300 |
Analyses courtesy of Smith aqueous geochemistry class.
Bull, W.B., 1964, Geomorphology of Segmented Alluvial Fans in Western Fresno County, California, U.S. Geol. Surv. Prof. Paper 352E, 129p.
Schumm, S.A., 1977, The Fluvial System, New York, Wiley.
Sharpe, R.P., Carey, D.L., 1976, Moving Rocks on the Racetrack Playa, Geol.Soc.Am. Bull. 87, p1704-1717
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