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GEOLOGICAL AGENTS & THEIR
Kaustubh J. Sane
HJD Institute of Technical
Education and Research, Kera
WORK OF WIND
• The wind acts in three different ways viz.
Erosion, Transportation, Deposition.
• Erosive work of wind:
– Three types
• The removal of sand particles and dust by strong wind
is called deflation.
• This is observed mainly in desert regions.
• In some deserts deflation may remove the sand from a
particular location and create a depressions.
• These depressions some times reaches the ground
water table. These deeper water filled depressions are
called as OASES.
• Wind deflation also produces another feature like
HAMMADA. It is bare rock surface which is called as
• Wind when consist of sand and dust particles
it becomes powerful agent.
• These type of erosion evolves rubbing,
grinding, polishing and abrading of rock
surface by wind is called wind abrasion.
• These type of process itself is responsible for
formation of various landforms viz. Yardangs,
pedestal rocks, ventifacts.
• These are elongated, low- lying ridges forming
overhangs above depression.
• These are formed in areas where rocks of
alternate hard and soft characters are lying
above one another with gentle slope.
• Pedestal rocks:
• These are also called as mashroom rocks.
• These are flat topped rock masses with
• These are small size rock fragments having
one, two three or more polished surfaces.
• The polishing of surface is carried out by
prolonged action of wind.
• As soon as polishing of one surface is achieved
the rock is overturned by strong wind and
again second face gets under action of wind.
• These wind polished and facetted fragments
are called ventifacts.
Most Effective in Moving Loose Material
• Suspension (Silt)
– Light silt grade particles are lifted up in to upper
layer and moves along with it.
• Saltation (Sand)
– It is a broadly conical heap of sand characterized
with two slope either side of a medial ridge or
• Term is used for wind blown deposits of silt
• Loess is an aeolian sediment formed by the
accumulation of wind-blown silt, typically in
the 20–50 micro-metre size range.
• It is usually homogeneous and highly porous
and is traversed by vertical capillaries.
• Dunes and loess offer complicated problem in construction.
• As dunes & loess are migrating they are moving structures.
• Methods applied in such conditions are;
– Establishing frontal belts of vegetation that can resist the
advancing of sand dunes.
– Construction of wind breakers around the area. These walls
check the velocities of approaching wind.
– Treating the sands locally with crude oil.
– In loess soil engineering problems is to deal with hydro
consolidation characteristics of soil.
– As loess soil gets settle down quickly in moisture, which is
dangerous foundation soil.