Mass Movement Types.
Some main types of mass movement. Variations
in water content and rates of movement produce a variety of forms.
A rockfall is simply a volume of rock made up of individual
pieces that fall independently through the air and hit a surface.
A debris avalanche is a mass of falling and tumbling rock,
debris, and soil. It is differentiated from a slower landslide
by the tremendous velocity of onrushing material. The extreme
danger of a debris avalanche results from its high speed and
consequent lack of warning. A landslide is a sudden rapid
movement of a cohesive mass of material (soil, rock, etc) that
is not saturated with moisture. It involves a large amount of
material failing simultaneously. A common type of slide is the
rotational slide or slump which occurs when surface
material moves along a concave surface. Frequently water is present
along this movement plane and acts as a lubricant. The simplest
form of rotational slump is when a small block of land shifts
downward. The upper surface of the slide appears to rotate backward
and often remains intact. When the moisture content of moving
material is high, the term flow is used. Flows include
earthflows and more fluid mudflows.
〔Memorial University of Newfoundland and the C.R.B. FoundationによるNewfoundland and Labrador
Heritageの『Natural
Environment』の『Landscape』の『Geological
Hazards and Disasters』の中の『Slope
Instability』から〕 |
