EROSIONAL & DEPOSITIONAL
BY NEHA GUPTA, M.SC(EVS)
• They are created by Glaciers,
Grinding an existing valley into a
Rounded shape with steep sides.
• Bowl shaped depression results
from Plucking rock from sides and
scooping out at base of Glacier.
TARN: Lake filled cirque basins.
• The arête is a thin ridge of
rock that is left separating
the two valleys.
• A sharped-edge pass or
saddle between two adjacent
• A horn results when glaciers
erode three or more arêtes,
usually forming a sharp-
U- SHAPED VALLEYS: Flat valley
bottoms and steep walls, result of shear
stress and glacial erosion along valley
• Through Glacial erosion they tend to
Widen, Deepen & Straighten valleys.
• Depth of valley Modification
dependent upon thickness of Glacial
HANGING VALLEYS: Tributary valleys
left hanging high above the main glacial
trough upon melting of glacial ice.
• FJORDS: Glacial valleys which
have been inundated by the
sea(i.e , a drowned U-shaped
• PATERNOSTER LAKES: A
string of Glacial Lakes in line
along a glaciated valley.
Erosion resulting from glacial action,
whereby the surface material is
removed and the rock fragments
carried by the glacier abrade, scratch,
and polish the bedrock.
Also known as scouring.
Abrasion scratches on underlying
bedrock pavement, evident upon
removal of glacial ice.
MORAINES: Layers or ridges of till
(unsorted glacial deposits) deposited
from glacial ice.
• Lateral moraines are parallel ridges
of debris deposited along the sides
of a glacier.
• In Medial Moraines, till deposited at
the juncture of two alpine glaciers.
• A terminal moraine forms at the end
of the glacier called the snout and marks
the maximum advance of the glacier.
• Ground moraines are till covered
areas with irregular topography and
no ridges often forming gently rolling
hills or plains.
• Streamlined ,tear-drop shaped,
asymmetrical hills composed of till .
• Tail of the drumlin points in
direction of ice movement.
• A kettles are fluvioglacial landform occurring as the result of blocks of ice calving from the
front of a receding glacier and becoming buried partially to wholly by glacial outwash.
• A kame is a geological feature, an irregularly shaped hill or mound composed of sand,
gravel and till that accumulates in a depression on a retreating glacier.
• An esker is a long, winding ridge of stratified sand and gravel, examples of which occur in
glaciated and formerly glaciated regions.
• An outwash plain, also called a sandur ,is a plain formed of glacial sediments deposited by
melt water outwash at the terminus of a glacier.
IMPACT OF CLIMATE CHANGE ON
Most Valley Glaciers have been in general retreat since the end of the little Ice Age
between 100-300 years ago.
• Rise in temperature appears to be the primary control(Global Warming) &
changes in winter accumulation.
• In absence of change in precipitaion, rise in T of 0.4 deg.celcius per decade would
eliminate the glaciers by 2100.
• Equilibrium line altitude(ELA) of tropical glacier is more sensitive to changes in
air temperature than that of mid-latitude glacier.
• 1 deg. Celcius rise in T during half of the year will have impact on ablation ,
annual mass balance & ELA.
• If the glacier is in equilibrium, the amount of precipitation in winter is matched
by melt in summer.
MASS BALANCE STUDIES
Glaciers are sensitive to climate change, due to changes in their
mass, contributing to the rate of sea level rise.
• To evaluate this, we need to know the rate of change of total
Multiplying specific mass balance for a typical glacier in each
region with the total glacier area of the region. Then sum over
Table 11.4: Estimates of historical contribution of glaciers to global average sea level rise.
Rate of sea-level rise
Meier (1984) 1900 to 1961
Trupin et al. (1992) 1965 to 1984
Meier (1993) 1900 to 1961
Zuo and Oerlemans (1997),
1865 to 1990 0.22 0.07a Observed temperature changes
with mass balance
1961 to 1990 0.3a
Dyurgeov and Meier (1997b) 1961 to 1990 0.25 0.10 Area-weighted mean of observed
mass balance for seven regions
Dowdeswell et al. (1997) 1945 to 1995 approx 0.13 Observed mass balance, Arctic only
Gregory and Oerlemans (1998) 1860 to 1990 0.15a General Circulation Model (GCM)
temperature changes with mass
balance sensitivities from Zuo and
1960 to 1990 0.26a
a These papers give the change in sea level over the period indicated, from which we have calculated the rate of sea level rise.
MASS BALANCE SENSITIVITY TO
TEMPERATURE & PRECIPITATION
• Change in ablation of a glacier is modelled using bT, the sensitivity of the
mean specific surface mass balance to temperature.
• One approach determines bT by energy balance modelling, includes
dependence on monthly temperature and precipitation changes.
• Another approach uses a degree-day method, in which ablation is
proportional to integral of mean daily temperature above freezing point.
• For seasonally uniform temperature rise, increase in precipitation of 20-
50% 0C-1 is required to balance increased ablation variations of regional
–scale hygric seasonality.
GLACIERS N GREENLAND &
• Indicates an addition of about 6% to the sea level contribution in 21st
• Using a degree day scheme, estimates that ablation of glaciers in the
Antarctica peninsula presently amounts to 0.008 to 0.055 mm Yr-1 of a
sea level, 1 to 9% of the contribution from outside Greenland & Antarctica
• Ablation increases non-linearly with temperature.
• Results suggest that the Antarctic & Greenland will together give 10-20%
of the sea level contribution in future decades.
• The Himalayas have nearly 1500 glaciers; it is estimated that these
glaciers cover an area of about 33000 Km2.
• Almost 675 of the glaciers in the Himalayan and Tienshan mountain
ranges have retreated in the past decade.
• The mean equilibrium-line altitude at which snow accumulation is equal
to snow ablation for glaciers is estimated to be about 50-80 m higher
than the altitude during the first half of the 19th century.
• Available records suggest that Gangotri glacier is retreating by about 30
m Yr-1 .
• A warming is likely to increase melting far more rapidly than
• As reported in IPCC(1998), glacial melt is expected to increase under
changed climate conditions, which would lead to increased summer flows
in some river systems for a few decades, followed by a reduction in flow
as the glaciers disappear.
TIBET AUTONOMOUS REGION
Tibet autonomous Region of china around nepal & bhutan are
receding at an alarming rate.
(Retreated 2km in the last 200 years.)