Evidence of Lava Dams in the Western Grand Canyon
By Cody VanderBusch
ABSTRACT
The controversy of how many dams and how they failed
has been on going. John Wesley Powell in
1887 was the first to observe ruminants of these dams. The previous number of dams was 3 until 1994
when W. Kenneth Hamlin concluded that there are 13. The dams are located in the western
Location and Geological Map of
the
(http://www.icr.org/research/sa/sa-r02.htm)
|
Dam |
Elevation (m) |
Height |
K-Ar Age |
Number of Flows |
Dam Length |
|
Water Fill Time |
Sediment Fill Time |
|
(m) |
(Ma) |
(km) |
(km) |
|||||
|
Prospect |
1200 |
699 |
1.8 |
3 |
? |
518 |
23 yr |
3018 yr |
|
Lava |
1050 |
560 |
? |
Several |
? |
? |
? |
? |
|
Toroweap |
927 |
424 |
1.2 |
5 |
16 |
283 |
2.6 yr |
345 yr |
|
Whitmore |
750 |
270 |
0.99 |
40+ |
29 |
173 |
240 days |
88 yr |
|
Ponderosa |
840 |
339 |
0.61 |
1 |
19 |
202 |
1.5 yr |
163 yr |
|
Buried Canyon |
744 |
255 |
0.89 |
8 |
? |
173 |
231 days |
87 yr |
|
Esplanade |
780 |
288 |
? |
8-Jun |
13 |
174 |
287 days |
92 yr |
|
"D" Dam |
689 |
191 |
0.58 |
40 |
? |
123 |
87 days |
31 yr |
|
|
678 |
180 |
? |
1 |
35 |
123 |
86 days |
30 yr |
|
Black Ledge |
610 |
111 |
0.55 |
1 |
138+ |
85 |
17 days |
7 yr |
|
Layered Diabase |
581 |
89 |
0.62 |
20 |
22 |
67 |
8 days |
3 yr |
|
Massive Diabase |
548 |
68 |
0.44 |
1 |
16 |
64 |
5 days |
1.4 yr |
|
Gray Ledge |
544 |
61 |
0.78 |
1 |
21 |
59 |
2 days |
0.9 yr |
Physical
Characteristics of Lava Dams And There Associated Lakes
(Table from http://www.icr.org/research/sa/sa-r02.html)
Outline
I.
Introduction
a.
Location
b.
When did these dams occur and how long did the last?
c.
How were they formed and where from?
d.
Were the dams all made the same way?
e.
Depths and sizes of the dams
f.
The effects of the dams had on the canyon
II.
Location
a.
Hamblin concluded that there were at least 13 dams
b.
Western Grand Canyon between
miles 177 and 254
III.
When and how long did these dams last?
a.
The dams lasted a total of 250,000 years during the
Pleistocene
b.
Each dam lasted 10,000 to 40,000 years
i.
We know this by making a geochemical analysis on the
flood deposits.
IV.
How were these dams formed and where from?
a.
From the Uinkaret volcanic field located north of
the Colorado River between
the Hurricane and Toroweap faults.
b.
Fissure eruptions of the Columbia River Basalt
V.
Were these dams all made the same way?
a.
There were 4 different ways that Hamblin classified
the 13 dams
i.
Single-flow dams
ii.
Massive dams
iii.
Dams composed of a sequence of relatively thin flows
iv.
Complex flows
VI.
The depths and sizes of the dams
a.
The sizes of the dams ranged from 2,330 to 203 ft above
the river
b.
The lake length varied from 324 to 37 miles long
VII.
What effects did these dams have on the canyon?
a.
Dam failures resulted in:
i.
Slope Failures
ii.
Gorge widening
VIII. Slope
failures
a.
Due to the added water to the slopes, the sediment
slides down slope
IX.
Gorge widening
a.
Flooding from dam failure created a mass flow of
water down the canyon creating more erosion than normal
X.
Conclusion
References
Austin, S. A. and
Rugg, S. H., 1998, Evidences For Rapid Formation and
Failure of Pleistocene “Lava Dams” of the Western Grand Canyon, Arizona,
Cerling, T. E., Fenton, C. R., Nash, B. P., Poreda, R. J., Webb, R. H., Geochemical Discrimination of Five Pleistocene Lava-Dam Outburst-Flood Deposits, Western Grand Canyon, Arizona, The Journal of Geology 112 (2004), pp. 91-110.
Hamblin, W. K., Late Cenozoic Lava Dams in the
http://www.sciencedaily.com/releases/2002/07/020722074554.htm, Accessed March 12, 2004
http://www.kaibab.org/geology/canform.htm,
Accessed April 27, 2004