Glacial and Periglacial Geomorphology

Glaciers and frozen ground are powerful agents of erosion and deposition, carving valleys, depositing moraines, and shaping the high-latitude and high-altitude landscapes left behind by past ice ages.

Definition

Glacial geomorphology is the study of landforms produced by the erosion and deposition of glaciers and ice sheets, and periglacial geomorphology is the study of landforms and processes associated with intense freezing and permafrost in cold, non-glacial environments.

Scope

This topic covers the geomorphic work of ice: glacial erosion and deposition and the landforms they create, the periglacial processes that operate around and beyond ice margins in permafrost terrain, and the evidence for past glaciations. It addresses cold-climate landscapes within process geomorphology.

Core questions

• How do glaciers erode and deposit material, and what landforms result?
• What processes shape permafrost and periglacial landscapes?
• What evidence records past ice ages?

Key theories

The glacial theory

Agassiz argued that erratic boulders, polished and striated bedrock, and moraines far from present glaciers record a former great ice age, establishing that ice sheets once covered large areas now ice-free.

Glacial erosion and deposition mechanics

Glaciers erode by abrasion and plucking and transport debris that is deposited as till and outwash, producing characteristic landforms such as U-shaped valleys, cirques, moraines, drumlins, and eskers.

Mechanisms

Moving ice abrades bedrock with entrained debris and plucks loosened blocks, carving cirques, arêtes, and U-shaped valleys. Sediment carried by the ice is released as unsorted till forming moraines and drumlins, while meltwater deposits sorted outwash and eskers. In periglacial settings, repeated freeze–thaw and permafrost dynamics drive frost heave, patterned ground, and solifluction, shaping cold-climate landscapes.

Clinical relevance

Glacial and periglacial deposits host important aquifers and aggregate resources, while permafrost dynamics and its thaw pose major engineering and climate-related hazards; past glacial records also constrain models of climate change and sea level.

History

Louis Agassiz established the glacial theory in 1840, overturning the idea that erratic boulders were deposited by a great flood. Subsequent work mapped the extent of Pleistocene ice sheets and developed the mechanics of glacial and periglacial processes that underpin modern cold-climate geomorphology.

Key figures

• Louis Agassiz
• Douglas Benn
• David Evans

Seminal works

• agassiz1840
• bennevans2010

Frequently asked questions

How can you tell a valley was carved by a glacier?

Glacially carved valleys typically have a broad U-shaped cross-section with steep walls and a flat floor, unlike the V-shaped valleys cut by rivers, and they are often accompanied by features such as cirques, hanging valleys, and moraines.