Research About debris avalanche

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Influence of Debris Avalanche Block Faces and Mixed Facies on the Evolution of the North Fork of the Toutle River Drainage (1980-Present), Mount St. Helens, WA

An integrated field and laboratory-based study is outlined that proposes the role that sedimentary, geomorphic, and vegetative variables have played in the recovery on the North Fork of the Toutle River (NFTR) following the May 18, 1980 eruption of Mount St. Helens. The abundant volcaniclastic detritus produced by this eruption temporarily overwhelmed drainage systems flowing from the crater including the NFTR. The sedimentary detritus delivered to the upper reaches of the NFTR including debris avalanche facies has had a profound effect on the Morpho-sedimentary character of this drainage system. Planning and hazard evaluation along the North and South Forks of the Toutle River as well as the main Toutle River depend upon a clear understanding of sediment balance within the stream system. Data gathered during the duration of this project will extend understanding of that balance by quantifying the relative contributions of volcanogenic sedimentary detritus from prominent source deposits.

 

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Limnological monitoring of some lakes of the Mount St. Helens National Volcanic Monument.

The monitoring program will sample the phytoplankton and zooplankton communities of Castle and Coldwater Lake. The sampling program will also include water samples which will be analyzed for soluble reactive phosphorus, total phosphorus, nitrate, major ions, dissolved oxygen, and conductivity. Temperature and water transparency will also be observed. The data will be analyzed to determine the structure of phytoplankton and zooplankton communities in these two lakes and the possible impacts of fish introduced into Coldwater Lake.

 

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Effects of elk and deer on early forest succession at Mount St. Helens

The objective of this study is to determine the role of elk and deer in the recovery of both natural and managed vegetation following volcanic disturbance. Additionally, we are interested in documenting the influence of elk and deer on vegetation establishment in areas that received different levels of volcanic impact. This goal will be achieved through a network of exclosures that will allow cross-site comparisons.

 

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Mount St. Helens Data Network

After the eruption of Mount St. Helens, the National Weather Service placed a series of precipitation and river gauges around the mountain. This data network was put in operation to alert forecasters of heavy precipitation events and/or rapid rises on the Toutle and Cowlitz Rivers or rapid falls in lakes in proximity to the mountain. This paper explains that data network.

 

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Community reassembly following volcanic disturbance: the ground dwelling beetles (Coleoptera)

This study documents the recovery of beetles within the volcanically disturbed areas of Mount St. Helens and should provide an index to the rate and stage of ecosystem recovery at various points in time since the eruption. Beetles are ideal for monitoring ecological recovery following disturbance as they represent a broad trophic array. The ground dwelling beetle fauna of forests and clearcut habitats were sampled using pitfall traps (10 traps/site) that were open from the time of spring snow melt to early autumn from 1982-1984 and again in 1987 and 1990. Sites sampled include undisturbed “reference” areas and three post-eruption habitats (ashfall, blowdown, and pyroclastic/debris flow).

 

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Small mammal recolonization on the Mount St. Helens volcano

The purpose of this study was to systematically document the initial survival and the subsequent recolonization of small mammal species into disturbed regions of Mount St. Helens, and to ascertain differences in early successional patterns among various habitat types and levels of disturbance. Trapping efforts have documented the recolonization of small mammals {Rodentia, Insectivora, Lagomorpha and Carnivora (Mustelidae)} into representative sites of four broadly defined montane habitats (forests, clearcuts, subalpine meadows and riparian ravines) that were subjected to increasing degrees of volcanic disturbance (undisturbed, ashfall, mud flow, tree blowdown, and pyroclastic/debris flow).

 

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Observation of recolonization of amphibians and reptiles in North Fork Toutle River debris avalanche.

Various reports indicate in situ survival of or early migration of some amphibians into regions of the blast zone following the major eruptions on May 1980. Investigators observed salamanders, frogs and toads as early as 1980 and 1981 in areas of heavy ashfall northeast of the crater. Survival at higher elevations likely was favored by snow and ice cover and the fact that many animals were in hibernacula.

 

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Plant recovery on the debris avalanche Key Words:

Seed dispersal and plant establishment have been monitored since 1980 on the debris avalanche created by the eruption of Mount St. Helens. The number of plants on the deposit increased over time to a high of almost 2 plants per square meter by 1983. The number of species per 250 meter square plot have increased to a mean of 10.3 in 1983 with 76 species being present over the entire deposit. Four years after the eruption only 30 percent of the species present before the eruption had reestablished themselves, and average plant cover was less than 1 percent. By 1989, plant cover had reached 18 percent.

 

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Distribution of plant detritus and recovery of plants in deposits of May, 1980 eruption of Mount St. Helens

This study seeks to identify types and sizes of plant material and distance and means of deposition in the May 1980 blast of Mount St. Helens. Types of plant material included pieces of moss, leaves, stems, roots, tree branches and trunks. Four types of transport were identified. The debris avalanche deposited plant material 23 km away. Mudflows (lahars) carried material 75 km to the Columbia River. The pressure blast removed vegetation in a 500 km2 area. Pyroclastic flows in conjunction with the plinian column spread plant debris for at least 75 km in a 110o arc to the north and east. These results are being compared with fossilized records of volcanic eruptions worldwide but especially those from Tertiary western United States.

 

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Ecosystem recovery on the debris avalanche

The object of this study is to monitor ecosystem recovery on the debris avalanche created by the May 1980 eruption of Mount St. Helens. Vegetation was significantly reduced in the blast area. Plant survival and diversity was apparently related to growth form. Plants with underground dormant buds survived best. Plant recovery has been correlated with moisture rather than physical structure of the substrate.

 

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