Glacial Erosional Forms

The theme of glacial erosion forms includes microforms and landforms produced by glacial erosion (e.g. striations, grooves, boulders, etc.). The recognition of these marks, their distribution and the observation of polarity criteria allow the interpretation of the direction and sense of ice flow and the reconstruction of the evolution of glacial transport for a given territory. Glacial erosion marks are represented on maps of surficial deposits as a dot and are superimposed on morphosedimentological zones.

The list of symbols is also available in PDF format.

↑ Other glacial erosion mark of known directionOther glacial erosion mark of unknown directionSmall, arched, hollow landform consisting of a concave wall pointing upstream and a floor inclined downstream. Usually in strings, rarely isolatedSmall, isolated, arched and hollow landform consisting of a convex upstream-facing wall and a downstream-inclined floor. Very rareChatter mark formed by conchoidal breaks caused by the subglacial transport of clasts under pressure that impact the bedrockMetric-sized glacial moulding or groove formed by subglacial abrasion processes due to the presence of erosive material (clasts) and water at the base of the ice. Known direction of flowMetric-sized glacial moulding or groove formed by subglacial abrasion processes due to the presence of erosive material (clasts) and water at the base of the ice. Unknown direction of flowMetric-sized glacial moulding or groove formed by subglacial abrasion processes due to the presence of erosive material (clasts) at the base of the ice. The floor of this type of landform is covered with chatter marksRelatively symmetrical rock outcrop with a rounded, polished surface, usually striated by glacial erosion and resembling a whale's back breaking through the water surfaceSmall, curvilinear break in bedrock, the concavity of which is oriented downstream of the ice fl ow. Generally arranged in stripes. This type of impact mark result from a boulder or clast being driven under the ice and carving discontinuous impact grooves on bedrockVarious forms of cavitation with smooth, rounded walls carved into bedrock. Generally caused by the erosive action of ice, meltwater and high-pressure subglacial sediments. The flow direction varies according to the type of form (muschelbruch, sichelwannen, comma-form, cavetto, etc.)Various forms of cavitation with smooth, rounded walls carved into bedrock. Generally caused by the erosive action of ice, meltwater and high-pressure subglacial sediments. Direction of flow cannot be determined (kettle, undulating surface)Small ridge elongated in the ice flow direction and associated with a resistant nodule of rock that protects the bedrock located downstream from differential erosionAsymmetrical rock outcrop oriented in the direction of the glacier flow and characterized, in the upstream part, by a gently sloping face shaped, polished and generally striated by the glacier. The part of the outcrop located downstream of the glacier is marked by a steeply sloping scraping faceAsymmetrical rock outcrop with a streamlined shape similar to that of a drumlin. Elongation parallel to the ice flow direction with a shaped, polished and generally striated surface due to glacial erosionNarrow incision in the bedrock displaying a downstream part that ends in a widening and abrupt deepening (nail head) resulting from the gradual attenuation of a clast dragged over the rock that led to tearing of a rock chipCentimetric scar left on a rock surface by the scraping of a clast in a subglacial position. The analysis allows for the determination of the ice flow directionCentimetric scar left on a rock surface by the scraping of a clast in a subglacial position. The analysis does not allow for the determination of the ice flow direction