The determination of snow avalanche frequency through tree-ring analysis and historical records at Ophir, Colorado

Deglaciation and postglacial treeline fluctuation in the northern San Juan Mountains, Colorado

“…Many of these sites are the subject of reports: Maher (1961Maher ( , 1963Maher ( , 1972, Andrews and others (1975), Elias (1982), Carrara andothers (1984, 1991), Elias and others (1991), Reasoner and Jodry (2000), and Toney and Anderson (2006). This information consists primarily of pollen analyses of radiocarbon-dated sediment cores, but it also includes sites where coniferous wood fragments and fossil insects were recovered and radiocarbon dated.…”

“…Snow avalanches can scar or strip branches off trees and, if the avalanches are large enough, they can snap tree trunks (Carrara, 1979) and locally lower timberline on steep slopes and in high basins. In many cases the avalanche is confined by steep gullies along valley walls until it reaches the valley floor, where it spreads out and may represent a hazard to manmade structures.…”

“…On 4 June 1978, it was suddenly and completely drained by the collapse of underground mine workings ( fig. 4) (Carrara and Mode, 1979;Marcus and Marcus, 1983;Carrara andothers, 1984, 1991). This unfortunate event had beneficial consequences for paleoclimate studies because the lake's sediments were incised by the escaping waters, which exposed a well-preserved archive of subfossil wood above present-day treeline.…”

“…Unpublished radiocarbon ages of coniferous wood fragments from a water well drilled near the town of Telluride in 1991, and 3. Unpublished radiocarbon ages of coniferous wood fragments, including AMS radiocarbon ages, from the Lake Emma site (these ages require a moderate revision of previous interpretations) (Carrara andothers, 1984, 1991). The sites are discussed in order of increasing elevation.…”

“…The draining of Lake Emma provided a unique opportunity for paleoclimatic studies because the lake's sediments were incised by the escaping waters, which exposed a well-preserved archive of subfossil coniferous wood fragments above present-day treeline. Fifty-three of these coniferous fragments were subsequently radiocarbon dated (some several times) (Carrara andothers, 1984, 1991), yielding one of the best-documented records of Holocene treeline fluctuations in North America. Because of concerns about anthropomorphic causes of global warming, the study and documentation of the natural variability in ecosystems is important in order to understand the possible effects of future climate change.…”