An erratic is a piece of rock that has been eroded and transported by a
glacier to a different area; it is left behind when the ice melts.
Glacial erratics give us information about the direction of ice movement
and distances of transport. Glacial erratics can be any size from small
pebbles to large boulders the size of a house.
This large, angular erratic is a granite boulder that was found near
Grey River in southern Newfoundland.
A perched boulder is a glacial erratic that has been transported by a
glacier and rests precariously at a different location then its source.
A large, angular boulder of granite perched on a ridge of granite was
left here by a glacier when it melted. This perched erratic occurs south
of Noel Paul's Brook, central Newfoundland.
A rock surface that has been scraped by glaciers moving over it. Rock
fragments frozen into the base of the ice scratched the underlying rock.
These scratches are called striations if they are small and grooves if
they are large. Scientists use these features to show the direction of
This photo, taken near Burgeo, southern Newfoundland, shows striations,
grooves and erratics on a glacially smoothed outcrop. Large fragments
can form long grooves in the rock surface as can be seen in the centre
of this picture.
|Glacial Striations and Sichelwannen
Striations are scratches formed on a rock surface by rock fragments
frozen into the bottom of a moving glacier. Sichelwannen are curved
grooves formed by water that was under immense pressure at the base of
Different types of erosion marks formed by glaciers occur on glaciated
bedrock. the straight scratches were formed by rock fragments being
dragged across the bedrock surface and are called striations. The curved
grooves going from left to right in this photo, across the striations
are sichelwannen. (Example from Hawkes Bay, northern Newfoundland).
A roche moutonnee is a knob or hill of bedrock that has been striated
and rounded by glaciers, with a gentle slope facing toward the up-ice
direction. The up-ice side (i.e., from where the glacier came) has been
smoothed by the same process that formed the striations as described
earlier. The down-ice side is usually jagged and rough because it has
been eroded by freeze-thaw processes that occurred in a cavity that
formed as the ice passed over the ridge.
This term is generally restricted to small-scale features as described
earlier. The feature pictured in the photo on the left, although very
large, displays the features of roche moutonne. The up-ice side of a
roche moutonnee contains well developed striations. These features are
common in central Newfoundland.
The photograph on the right shows
a large, gently sloping hill with one steep side formed by a glacier
moving from right to left. This example is from the Mount Margaret area,
St. Lawrence, Newfoundland.
|Glacial Outwash Delta
Stratified sediments washed out from a glacier by meltwater rivers and
deposited where the river flowed into the sea.
An example of bedded, unconsolidated, glacial sand and gravel deposited
where a meltwater stream flowed into the sea, from the Springdale area,
central Newfoundland. Sea-levels were much higher than present in many
parts of the province at the end of the last Ice Age.
Unsorted and unstratified material deposited by a glacier.
The photo on the left is a close-up of till showing its unsorted and
unstratified nature. (central Newfoundland).
The photo on the
right shows unsorted (i.e., all sizes of particles mixed together) and
unstratified debris carried by a glacier and left by the retreating
(melting) ice. Example from the Baie Verte area, northern Newfoundland.