scholarly journals Talus fabric, clast morphology, and botanical Indicators of Slope Processes on the Chaos Crags (California Cascades), U.S.A.

2002 ◽  
Vol 52 (1) ◽  
pp. 47-68 ◽  
Author(s):  
Francisco L. Pérez
Keyword(s):  
Debris Flows ◽  
Snow Avalanches ◽  
Mass Wasting ◽  
Rectilinear Segment ◽  
The North ◽  
Normal Mass ◽  
Volcanic Debris ◽  
Dome Collapse ◽  
Geomorphic Processes ◽  
Chaos Crags

AbstractThe Chaos Crags, a group of dacite domes in the Cascades Mtns (California), were affected by volcanic debris avalanches ca. 1675 A.D.; these left a sizable deposit and a scar on the north mountain flank, now covered by talus. This report examines the fabric and morphology of talus debris, their spatial variation, and the geomorphic processes presently affecting the slope. The talus presents a bi-segmented profile with a steep upper rectilinear segment and a shorter concave, basal zone. Debris are sorted by size both along (larger clasts downslope) and across the talus (larger particles below the cliffs). Shape sorting is weaker, but clast sphericity increases, and elongation decreases, toward the footslope. Upper-talus fabrics (long axes parallel to talus plane and slope) show that clasts there move by sliding, while basal blocks are deposited by rockfall, which causes more iso- tropic fabrics. Field observations and botanical evidence indicate the overall significance of grain flows, which are prevalent duetoanabundantsupplyofrubbleonthe upper talus. Comparison with similar recent slopes and repeat photography suggest the Chaos talus formed swiftly following dome collapse, when much debris may have collected below the unstable rockwalls. The talus has experienced only modest sedimentation during the 20thcentury, and is currently affected by 'normal' mass-wasting processes, which also include snow avalanches and debris flows.

Geomorphic process-disturbance corridors: a variation on a principle of landscape ecology

2001 ◽  
Vol 25 (2) ◽  
pp. 237-238 ◽  
Author(s):  
David R. Butler
Keyword(s):  
Landscape Ecology ◽  
Debris Flows ◽  
Snow Avalanches ◽  
Riparian Corridors ◽  
Geomorphic Process ◽  
The Matrix ◽  
Definition Of ◽  
Matrix Patches ◽  
Geomorphic Processes ◽  
Source And Sink

The paradigm of landscape ecology describes a landscape as a mosaic of landscape elements including the matrix, patches and corridors. Corridors are described as linear disruptions to the matrix, produced by anthropogenic actions or by streams which produce riparian corridors. Snow avalanches and debris flows are other geomorphic processes that should be considered as geomorphic process corridors rather than as disturbance patches. They possess requisite linearity, and they accomplish the five functions of a corridor: habitat, conduit, filter, source and sink. The definition of corridor in landscape ecology should be modified to embrace the concept of geomorphic process corridors.

The late Wisconsinan olistostrome of the lower Coppermine River valley, Northwest Territories

1986 ◽  
Vol 23 (11) ◽  
pp. 1700-1708 ◽  
Author(s):  
Denis A. St-Onge ◽  
Jean Lajoie
Keyword(s):  
Debris Flows ◽  
Late Quaternary ◽  
Fine Sand ◽  
Coarse Sand ◽  
Coarse Fraction ◽  
River Valley ◽  
Glacial Lake ◽  
The North ◽  
Geologic Record ◽  
Coppermine River

The late Quaternary olistostrome exposed in the lower Coppermine River valley fills a paleovalley that ranges in apparent width from 150 to 400 m and was cut into Precambrian bedrock before the last glaciation. The olistostrome is here named the Sleigh Creek Formation. The coarse fraction of the formation is matrix supported; beds are massive or reversely graded and have sharp, nonerosive contacts. These characteristics suggest deposition of the coarse fraction by debris flows. The olistostrome sequence is bracketed by, and wedged into, a marine rhythmite sequence, which indicates that deposition occurred in a marine environment.About 10 500 years BP glacier ice in the Coronation Gulf lowland dammed the valley to the south, which was occupied by glacial Lake Coppermine. Sediments accumulated in this lake in a 30 m thick, coarsening upward sequence ranging from glaciolacustrine rhythmites of silt and fine sand at the base to coarse sand alluvium, and deltaic gravels at the top. As the Coronation Gulf lowlands became ice free, the Coppermine River reoccupied its former drainage course to the north. The steep south to north gradient and rapid downcutting by the river through the glacial lake sediments produced unstable slope conditions. The resulting debris flows filled a bedrock valley network below the postglacial sea level, forming the diamicton sequence.The interpretation of the Sleigh Creek Formation raises questions concerning silimar diamicton deposits usually defined as "flowtills." More generally, the results of this study indicate that care must be used when attempting paleogeographic reconstructions of "glaciogenic" deposits in marine sequences in any part of the geologic record.

scholarly journals Snow Level Characteristics and Impacts of a Spring Typhoon-originating Atmospheric River in the Sierra Nevada, USA

2018 ◽  
Author(s):  
Benjamin Hatchett
Keyword(s):  
Sierra Nevada ◽  
Debris Flows ◽  
Heavy Precipitation ◽  
Extratropical Cyclone ◽  
Snow Avalanches ◽  
Northeast Pacific ◽  
Atmospheric River ◽  
Super Typhoon ◽  
Wet Snow

On 5-7 April 2018 a landfalling atmospheric river resulted in widespread heavy precipitation in the Sierra Nevada of California and Nevada. Observed snow levels during this event were among the highest snow levels recorded since observations began in 2002 and exceeded 2.75 km for 31 hours in the northern Sierra Nevada and 3.75 km for 12 hours in the southern Sierra Nevada. The anomalously high snow levels and over 80 mm of precipitation caused flooding, debris flows, and wet snow avalanches in the upper elevations of the Sierra Nevada. The origin of this atmospheric river was super typhoon Jelawat, whose moisture remnants were entrained and maintained by an extratropical cyclone in the northeast Pacific. This event was notable due to its April occurrence, as six other typhoon remnants that caused heavy precipitation with high snow levels (mean = 2.92 km) in the northern Sierra Nevada all occurred during October.

scholarly journals Landslides after wildfire: initiation, magnitude, and mobility

Landslides ◽  
2020 ◽  
Vol 17 (11) ◽  
pp. 2631-2641
Author(s):  
Francis K. Rengers ◽  
Luke A. McGuire ◽  
Nina S. Oakley ◽  
Jason W. Kean ◽  
Dennis M. Staley ◽  
...  
Keyword(s):  
Debris Flows ◽  
Rainfall Intensity ◽  
Ground Cover ◽  
First Year ◽  
Mass Wasting ◽  
Soil Infiltration ◽  
Infiltration Capacity ◽  
The Past ◽  
Long Duration ◽  
Southwestern Usa

Abstract In the semiarid Southwestern USA, wildfires are commonly followed by runoff-generated debris flows because wildfires remove vegetation and ground cover, which reduces soil infiltration capacity and increases soil erodibility. At a study site in Southern California, we initially observed runoff-generated debris flows in the first year following fire. However, at the same site three years after the fire, the mass-wasting response to a long-duration rainstorm with high rainfall intensity peaks was shallow landsliding rather than runoff-generated debris flows. Moreover, the same storm caused landslides on unburned hillslopes as well as on slopes burned 5 years prior to the storm and areas burned by successive wildfires, 10 years and 3 years before the rainstorm. The landslide density was the highest on the hillslopes that had burned 3 years beforehand, and the hillslopes burned 5 years prior to the storm had low landslide densities, similar to unburned areas. We also found that reburning (i.e., two wildfires within the past 10 years) had little influence on landslide density. Our results indicate that landscape susceptibility to shallow landslides might return to that of unburned conditions after as little as 5 years of vegetation recovery. Moreover, most of the landslide activity was on steep, equatorial-facing slopes that receive higher solar radiation and had slower rates of vegetation regrowth, which further implicates vegetation as a controlling factor on post-fire landslide susceptibility. Finally, the total volume of sediment mobilized by the year 3 landslides was much smaller than the year 1 runoff-generated debris flows, and the landslides were orders of magnitude less mobile than the runoff-generated debris flows.

Biostratigraphic, paleogeographic, and tectonic implications of Late Ordovician conodonts from the Grog Brook Group, northwestern New Brunswick

1983 ◽  
Vol 20 (4) ◽  
pp. 651-671 ◽  
Author(s):  
Godfrey S. Nowlan
Keyword(s):  
New Brunswick ◽  
North Atlantic ◽  
Debris Flows ◽  
Late Ordovician ◽  
Thrust Faulting ◽  
The North ◽  
Atlantic Province ◽  
Unusual Distribution ◽  
Alternative Hypotheses ◽  
Structural High

Diverse conodont faunas recovered from the Grog Brook Group in northwestern New Brunswick indicate a Late Ordovician, probably Gamachian, age. The conodonts are of mixed provincial affinity including components of the North Atlantic Province (e.g., Hamarodus, Icriodella, Periodon, and Protopanderodus) and taxa representing shallow (e.g., Rhipidognathus) to deeper water environments (e.g., Phragmodus) in the Midcontinent Province. Elements of Amorphognathus ordovicicus Branson and Mehl numerically dominate the faunas that together with sparse representatives of Gamachignathus ensifer McCracken, Nowlan and Barnes suggest a latest Ordovician age. The beds from which the conodont faunas have been recovered are interpreted as distal debris flows that originated at the basin margin and brought Midcontinent Province conodonts down the slope to mix with indigenous North Atlantic Province faunas. The faunas are correlative with those from the Matapedia Group (previously thought to overlie the Grog Brook Group) and their occurrence suggests at least partial lateral equivalence of the two units.The conodonts recovered are only slightly thermally altered. Two alternative hypotheses are proposed to explain the juxtaposition of relatively unaltered conodonts of the Grog Brook Group and highly altered forms from the Matapedia Group. The first suggests that thrust faulting took place in the Late Ordovician – Early Silurian and that this process and later normal faulting account for the unusual distribution of conodont colour alteration. The second possibility is that the strata of the Grog Brook Group in the section examined were deposited on a structural high and overlain by little or no sediment of the Matapedia Group; however, such a structural high must have had access to a source of Midcontinent Province conodonts. Acadian thrusting then brought higher grade Matapedia Group strata into contact with this part of the Grog Brook Group.

Glacigenic debris flows on the North Sea Trough Mouth Fan during ice stream maxima

1998 ◽  
Vol 152 (1-3) ◽  
pp. 217-246 ◽  
Author(s):  
E.L King ◽  
H Haflidason ◽  
H.P Sejrup ◽  
R Løvlie
Keyword(s):  
North Sea ◽  
Debris Flows ◽  
The North ◽  
Ice Stream ◽  
The North Sea
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