Our Beautiful World


Debris avalanche and flow / Skred eller flom av løst materiale



Downstream view of the North Fork Toutle River valley, north and west of St. Helens,
shows part of the nearly 2/3 cubic miles (2.3 cubic kilometers) of debris avalanche
that slid from the volcano on May 18, 1980.
The avalanche traveled approximately 15 miles (24 kilometers) downstream at a velocity exceeding 150 miles per hour (240 km/hr).
It left behind a hummocky deposit with an average thickness of 150 feet (45 meters) and a maximum thicknes of 600 feet (180 meters).

USGS Photograph taken on November 30, 1983, by Lyn Topinka.



Debris avalanche:
A rapid and unusually sudden sliding or flowage of unsorted masses of rock and other material. As applied to the major
avalanche involved in the eruption of Mount St. Helens (1980),
a rapid mass movement that included fragmented cold and hot
volcanic rock, water, snow, glacier ice, trees, and some hot
pyroclastic material. Most of the May 18 deposits in the upper
valley of the North Fork Toutle River and in the vicinity of Spirit
Lake are from the debris avalanche. (Foxworthy and Hill, 1982)

The very rapid and usually sudden sliding and flowage of an
unsorted mixture of soil and weathered (altered) rock
Moves away from a volcano at high speed.

Debris flow:
A flowing mixture of water and rock debris, sometimes referred to as a lahar (originating at a volcano) or mudflow.

 


Debris skred:
Et hurtig og uvanlig plutselig skred eller flom av
usorterte steinmasser og annet materiale. Anvendt på
hovedskredet i forbindelse med utbruddet av St.Helens i
USA, en hurtig masseflytning som inkluderte fragmenter av
kalde og varme vulkanske steiner, vann, snø, biter av isbreen,
trær og varmt pyroklastisk materiale.

Debris flom: En blanding av vanntrukkene steinrester
(ofte pimpestein), som flyter nedover som følge av
gravitasjonskraften. Også kalt lahar eller mudderflom.
Kan nå så langt som 250 km eller mer, nedover et dalføre, og på
grunn av sitt innhold tette igjen hele elvesystemer.





bukkm.gif
ANIMALS

over 250

birdm.jpg
BIRDS

over 500

flower.jpg
FLOWERS

over 225
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