Till - Citizendia

This article is about glacial sediments. For other uses, see Till (disambiguation).

Glacial till with tufts of grass

Till is unsorted glacial sediment. "Glacial" and "Glaciation" redirect here For the geological periods see Glacial period. Glacial drift is a general term for the coarsely graded and extremely heterogeneous sediments of glacial origin. Sediment is any particulate matter that can be transported by fluid flow and which eventually is deposited as a layer of solid particles on the bed or bottom of a body of Glacial till is that part of glacial drift which was deposited directly by the glacier. It may vary from clays to mixtures of clay, sand, gravel and boulders. Clay is a naturally occurring material composed primarily of fine-grained Minerals which show plasticity through a variable range of Water content, and Sand is a naturally occurring Granular material composed of finely divided rock and Mineral particles Gravel is rock that is of a specific Particle size range In Geology, gravel is any loose rock that is larger than two millimeters (2mm In Geology, a boulder is a rock with grain size of usually no less than 256 mm (10 Inches diameter Clay in till may form in spherical shapes called till balls. "Globose" redirects here See also Globose nucleus. A sphere (from Greek σφαίρα - sphaira, "globe If a till ball rolls around in a stream, it may pick up rocks from the streambed and become covered by rocks; thence it is known as an armored till ball.

Till is deposited at the terminal moraine, along the lateral and medial moraines and in the ground moraine of a glacier. Moraine refers to any glacially formed accumulation of unconsolidated glacial debris (soil and rock which can occur in currently glaciated and formerly glaciated regions such as those Moraine refers to any glacially formed accumulation of unconsolidated glacial debris (soil and rock which can occur in currently glaciated and formerly glaciated regions such as those Moraine refers to any glacially formed accumulation of unconsolidated glacial debris (soil and rock which can occur in currently glaciated and formerly glaciated regions such as those Moraine refers to any glacially formed accumulation of unconsolidated glacial debris (soil and rock which can occur in currently glaciated and formerly glaciated regions such as those As a glacier melts, especially a continental glacier, large amounts of till are washed away and deposited as outwash in sandurs by the rivers flowing from the glacier and as varves in any proglacial lakes which may form. "Glacial" and "Glaciation" redirect here For the geological periods see Glacial period. A sandur (plural sandar is a glacial outwash Plain formed of Sediments deposited by meltwater at the terminus of a Glacier. "Riverine" redirects here For the use of that term in Maritime geography, see there A varve is an annual layer of Sediment or Sedimentary rock. The word 'varve' is derived from the Swedish word varv whose In Geology, a proglacial lake is a lake formed either by the Damming action of a Moraine or Ice dam during the retreat of a melting glacier or Till may contain alluvial deposits of gems or other valuable ore minerals picked up by the glacier during its advance, for example the diamonds found in Wisconsin, Indiana, and Canada. Alluvium (from the Latin, alluvius, from alluere, "to wash against" is Soil or Sediments deposited by a river or other running A gemstone or gem, also called a precious or semi-precious stone, is a piece of attractive Mineral, which &mdash when cut and polished &mdash An ore is a volume of rock containing components or Minerals in a mode of occurrence that renders it valuable for mining In Mineralogy, diamond is the allotrope of carbon where the carbon atoms are arranged in Wisconsin ( or wɪˈskɑnsɨn (French Ouisconsin) is one of the fifty United States of America, located in the north central part of the United States The State of Indiana ( was the 19th US state admitted into the union Country to "Dominion of Canada" or "Canadian Federation" or anything else please read the Talk Page Prospectors use trace minerals in tills as clues to follow the glacier upstream to find kimberlite diamond deposits and other types of ore deposits. Prospecting is the physical search for Minerals Fossils precious metals or mineral specimens and is also known as Fossicking. Kimberlite is a type of potassic Volcanic rock best known for sometimes containing Diamonds It is named after the town of Kimberley in South Africa

Tillite

In cases where till has been indurated or lithified by subsequent burial into solid rock, it is known as the sedimentary rock tillite. Lithification (from the Greek word lithos meaning 'rock' and the Latin -derived suffix -ific) is the process in which Sediments compact Sedimentary rock is one of the three main rock types (the others being igneous and Metamorphic rock) Matching beds of ancient tillites on opposite sides of the south Atlantic Ocean provided early evidence for continental drift. Continental drift is the movement of the Earth 's Continents relative to each other The same tillites also provided the key evidence for the Precambrian Snowball Earth glaciation event. The Precambrian ( Pre-Cambrian) is an informal name for the supereon comprising the eons of the Geologic timescale that came before the current The Snowball Earth Hypothesis as it was originally proposed]] Evidence The Snowball Earth hypothesis was originally devised to explain the apparent presence of

Types of till

There are various types of classifying tills:

primary deposits – these were laid down directly by glacier action
secondary deposits – these have undergone reworking (e. g. fluvial transport, erosion, etc)

Traditionally (e. g. Dreimanis, 1988), a further set of divisions has been made to primary deposits, based upon the method of deposition. Aleksis Dreimanis (b August 13, 1914 in Riga) is an award winning Quaternary geologist.

Lodgement tills – sediment which has been deposited by plastering of glacial debris from a sliding glacier bed.
Deformation tills – Sediment which has been disaggregated and (usually) homogenised by shearing in the sub glacial deformed layer.
Melt out tills – Released by melting of stagnant or slowly moving debris-rich glacier ice and deposited without subsequent transport or deformation. Split up into sub glacial melt out till (melting of debris rich ice at the bottom of the glacier) and supraglacial melt-out till (melting of ice on the glacier surface).
Sublimation till – similar to melt out till, except the ice is lost through sublimation rather than melt. Often occurs only in extremely cold and arid conditions, mainly in Antarctica.

Some (e. g. Van der Meer et al. 2003) have suggested that these till classifications are outdated and should instead be replaced with only one classification, that of deformation till. The reasons behind this are largely down to the difficulties in accurately classifying different tills, which are often classified based on inferences of the physical setting of the till rather than till fabric or particle size analysis data.