All sediments of glacial origin are called "drift".
These sediments are classified into two types:
1.- TILLS: materials deposited directly by the glacier.
2.- STRATIFIED
GLACIER DRIFTS: sediments left by
the melting water of the glacier.
TILLS:
/ They are deposited as the ice melts, leaving behind its
burden of rock fragments.
/ They are mixtures of rocky grains of different sizes. Many are scratched
and polished by the erosive action of the glacier.
/ The large blocks are called "GLACIAL ERRATICS" and may have been transported between
500-1000 kilometers from their original location.
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https://www.antarcticglaciers.org/wp-content/uploads/2020/03/erratic_cartoon-1024x853.png
/ The most common term to denominate the forms constituted
by glacial deposits is "MORAINE",
which would group all the forms composed of tills. They are accumulations of
rocky material transported and deposited by glacial tongues.
/ The TYPES OF MORAINES are:
1.- Lateral moraine: they are
accumulations of till that run parallel to the sides of the alpine valley next
to the glacial tongue. They are usually produced in alpine glaciers when it
crosses a mountain valley.
2.- Medial moraine: they are
produced when two lateral moraines merge and form a single ice stream. The till
that was previously on the sides joins together and forms a single band of
sediments. It is exclusive to alpine glaciers.
3.- Terminal moraine: it is a
mound of till generated at the end of a glacier. It occurs when the equilibrium
between ablation and ice accumulation is reached. The ice melts and evaporates,
meanwhile it continues to flow forward and deposit more and more till, causing
the terminal moraine to grow.
4.- Bottom moraine: occurs when
the glacier, after having formed a terminal moraine, begins to recede. It is
this setback that generates a gently undulating layer of till.
5.- Retreat moraine: The process
of ablation and feeding of the glacier is repeatedly balanced and unbalanced
until the glacier completely vanishes. The terminal moraines that form during
these equilibration/disequilibrium processes are called retreat moraines.
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https://www.geocaching.com/geocache/GC8586B_brooklyn-street-moraine?guid=4d92a03a-1614-43a9-8ecc-e841734e0a8f
/ Another of the forms constituted by glacial deposits are the “DRUMLINS”. They are smooth, elongated, aerodynamic and parallel hills generated by cap glaciers. They are mainly composed of till. The height ranges between 15-50 meters. Its length can reach up to 1 kilometer. They do not appear isolated but form fields of drumlins.
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https://www.pmfias.com/wp-content/uploads/2015/12/Glacial-Depositional-Landforms-eskers-morains.jpg |
/ They are not deposited directly by the glacier, but are carried away by
currents of melting water from the glacier.
/ They are finer and lighter sediments (sand, gravel, rock flour) that are
transported beyond the glacier.
/ TYPES:
1.- Alluvial
plains: when the terminal
moraine forms, the glacier water cascades over the till. The sediment-laden
water is displaced and leaves the glacier, but quickly loses speed. Then a
network of channels begins to be created adjacent to the edge of the terminal
moraine.
2.- Valley train: it is similar
to the previous one, but it receives this name when it appears in a mountain
valley.
3.- Kettle: they are holes generated
by blocks of ice that have remained stagnant in the valley trains or alluvial
plains. These ice blocks, together with the sediments, melt and produce a lake
with a diameter between 2-10 kilometers, with a depth of less than 10 meters.
4.- Kame: steep slopes or mounds
generated by the melting of stagnant ice. On alpine glaciers kame terraces can
be found along the valley sides.
5.- Esker: is a long, narrow,
winding ridge made up of sand and gravel. They are generated by rivers of
meltwater flowing over, into, and under an immobile stagnant glacial ice mass.
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https://www.cs.mcgill.ca/~rwest/wikispeedia/wpcd/images/57/5754.png
