Geoscience Reference
In-Depth Information
compared to observations in other mountain ranges, but the distinct pattern and
spatial clustering of increasing displacements warrants future investigation.
5.5.3 Analysis of Geomorphic Variables
California rock glacier is much larger in terms of area and thickness compared to
most Front Range rock glaciers (Janke
2005b
). Cliff retreat rates for California rock
glacier (1.70-2.82 mm/yr) are also greater than the Front Range (0.17-1.33 mm/yr).
This illustrates the relative inactivity of physical weathering in the Front Range com-
pared to other mountains (Caine
1974
;Humlum
2000
). High mountain streams and
melt water from snowpack contain a large concentration of ions in their dissolved
load. Because dissolved load is not visible, it is often neglected; however, given
the continuous nature in which chemical weathering operates, the magnitude may
be comparable if not greater than the amount of physical weathering (Vitek et al.
1981
).
The California rock glacier most likely contains a notable amount of ice
(1-10 m average thickness). Williams et al. (
2007
) found that seven Rocky
Mountain rock glaciers emit higher nitrate concentrations (69
μ
moles/L) compared
moles/L). At Green Lakes 5 rock glacier, Mg
2+
concentrations increased to more than 4,000
to snow (7
μ
moles/L) and rain (25
μ
eq per L in September; Ca
2+
were
μ
eq per L; and SO
4
2
−
greater than 4000
μ
reached 7000
μ
eq per L (Williams et al.
2006
).
A more reliable indicator of ice content and thickness could be estimated with
geophysical surveys such as those that utilize Ground Penetrating Radar (GPR).
GPR has been used on rock glaciers to locate subsurface inclinations, debris rich
or supersaturated layers, ice, water flow paths, and bedrock foundations (Berthling
et al.
2000
; Isaksen et al.
2007
; Vonder Mühll et al.
2002
; Hausmann et al.
2007
;
Monnier et al.
2008
; Fukui et al.
2008
). A better measurement of ice thickness would
help better assess the potential impact on nearby aquatic ecosystems.
5.5.4 Hazard Assessment
Although no major slope processes, such as rockfalls, surface collapse features,
outburst floods from supraglacial lakes from melting snow or ice, or significant
increases in rates of flow were observed, the combination of remote sensing, GIS,
and field techniques provides a useful assessment of the current status of the
California rock glacier. The region where rates of flow were recently increasing
should be examined in more detail; a greater hazard potential could exist if the rock
glacier were to advance and override nearby forests as has been observed in the
nearby San Juan Mountains of Colorado. In other areas of the world that are expe-
riencing more significant warming and have greater population densities, the fact
that a temperature increase can induce rock glacier advance rather than retreat is of
concern. Rocks, which are sporadically deposited at angles in excess of 40
◦
,arenow
