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Flow. The third type of movement common to mass-wasting processes is termed flow.
Flow occurs when material moves downslope as a viscous fluid. Most flows are saturated with
water and typically move as lobes or tongues.
Rate of Movement. When mass-wasting events make the news, a large quantity of
material has in all likelihood moved rapidly down a steep slope and has had a disastrous effect
upon people and property. Indeed, during events called rock avalanches, rock and debris can
hurtle downslope at speeds exceeding 200 km per hour.
Based on the type of material involved, the kind of motion displayed, and the velocity of
the movement scientists classify the following types of mass wasting: slumps, rockslides, debris
flows, earthflows and creeps.
Slump refers to the downward sliding of a mass of rock or unconsolidated material
moving as a unit along a curved surface. Usually the slumped material does not travel
spectacularly fast or very far. This is a common form of mass wasting, especially in thick
accumulations of cohesive materials such as clay. Slump commonly occurs because a slope has
been oversteepened.
Rockslides occur when blocks of bedrock break loose and slide down a slope. If the
material is largely unconsolidated, the term debris slide is used instead. Such events are among
the fastest and most destructive mass movements.
Debris flow is a relatively rapid type of mass wasting that involves a flow of soil and
regolith containing a large amount of water. Debris flows composed mostly of volcanic materials
on the flanks of volcanoes are called lahars.
Earthflows most often form on hillsides in humid areas during times of heavy
precipitation or snowmelt. When water saturates the soil and regolith on a hillside, the material
may break away, leaving a scar on the slope and forming a tongue- or teardrop-shaped mass that
flows downslope.
Creep is a type of mass wasting that involves the gradual downhill movement of soil and
regolith. One factor that contributes to creep is the alternate expansion and contraction of surface
material caused by freezing and thawing or wetting and drying.
When soil is saturated with water, the soggy mass may flow downslope at a rate of a few
millimeters or a few centimetres per day or per year. Such a process is called solifluction
(literally, “soil flow”). It is a type of mass wasting that is common wherever water cannot escape
from the saturated surface layer by infiltrating to deeper levels. A dense clay hardpan in soil or
an impermeable bedrock layer can promote solifluction.

Task 2. Build up a glossary to the most important terms used in the text.

Task 3. Fill in the gaps in the following definitions with the correct terms (see the
text):
1. … represents blocks of bedrock breaking loose and sliding downslope.
2. … is the downward sliding of a mass of rock or unconsolidated material moving as a unit
along a curved surface.
3. … is an unconfined flow of saturated, clay-rich soil that most often occurs on a hillside in
a humid area following heavy precipitation or snowmelt
4. …. is a relatively rapid flow of soil and regolith containing a large amount of water.

Task 4. On the basis of the text try to draw a scheme of classification of mass-
wasting processes and its types.

Task 5. Write down a summary of the text using the key terms.

Task 6. Give a short report about mass wasting processes and their location in
Ukraine.