Depositional features

Glaciers act as conveyor belts, transporting boulders and material along with the flow.  Here are key terms and images of glacial deposits:

ERRATIC (Glacially-transported boulder)

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TILL (Unsorted (fine to boulder-sized) sediments deposited at the base of the glacier.)

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MORAINE (Ridge containing unsorted sediment deposited at the glacier’s melting edges.  Essentially, these ridges mark the outline of where a glacier has extend to in the past.)

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ESKER (Sinuous ridge of well sorted (by size), well rounded cobbles and sands deposited as the glacier or ice sheet retreats.  Eskers form within the plumbing of a glacier where melt water flowing through the glacier sorts and rounds the sediment.  Many eskers in Maine have roads built on top of them.)

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KETTLE HOLE (A circular depression in the ground, usually now a bog, was once a large chunk of ice that broke off of the glacier during retreat and outwash built up around the ice chunk until it melts (picture below).)

Photograph of a circular kettle hole that has now filled in with finer sediment.

Photograph of a circular kettle hole that has now filled in with finer sediment.

OUTWASH PLAIN (Gravel, sand, and silts transported by glacial melt water (rivers and streams) away from the glacier and deposited in valleys or on relatively flat land.  These are useful deposits for road and building construction.)

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DELTA (Technically water-related (fluvial) deposits, but there are many deltas above sea level in New England that mark the presence of higher (relative) sea level during the last ice age (when the land was depressed in New England because of the weight of the Laurentide Ice Sheet) or mark a location where a lake once was (possibly moraine- or ice-dammed).)

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2 responses to “Depositional features

  1. Pingback: Humans using glacial geology | Rock Paper Glacier!·

  2. Pingback: Glacier Plumbing | Rock Paper Glacier!·

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