Britannica Sources used in this answer

What materials make up glacial till?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

esker: Nunavut — glacial landform Eskers, or narrow ridges of gravel and sand left by a retreating glacier, wind through western Nunavut, Canada, near the Thelon River.

Glacial till is an unsorted, non-stratified material deposited directly by glacial ice. It is typically composed of a mixture of rock fragments and boulders embedded within a fine-grained matrix of sand, mud, or clay. Because it is deposited from ice rather than water, the fragments are often angular and sharp, frequently bearing striations, grooves, or facets from being ground against the glacier bed.12

The exact composition of till varies depending on the materials available to the glacier during its advance. For example, some deposits may consist primarily of deformed lake clays, while others are composed of bulldozed river sands and gravels. These deposits may also contain erratics—boulders of a rock type different from the underlying bedrock—which can help geologists trace the movement of ice sheets.2

Depending on how they are deposited, these materials are categorized into types such as basal till (often referred to as lodgment till) or ablation till.12