Glacial Erratic

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.

Perched Boulder

A perched boulder is a glacial erratic that has been transported by a glacier and rests precariously at a different location than 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.

Glacial Pavement

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 ice movement.

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 a glacier.

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).

Roche Moutonnee

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.

Till

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.