Flyttblock

Flyttblock is a term used in geology to describe a large rock or rock fragment that has been transported by glacial ice from its original location and deposited somewhere else after the ice melted. The Swedish word translates roughly to a “moved block.”

Formation and characteristics: Flyttblock form when a moving glacier cores up and carries blocks of bedrock from its substrate. These blocks can range from small boulders to massive stones and are often of a rock type different from the local bedrock where they are left. They may show signs of glacial transport such as smooth, abraded surfaces, striations, or glacial polish. Because they originate away from their current setting, their lithology can be markedly different from surrounding rocks.

Distribution and identification: Flyttblock are common in regions formerly covered by ice sheets, including Scandinavia and other parts of Northern Europe. They can occur as solitary blocks or as components of moraine fields. Identifying a flyttblock involves comparing the stone’s mineralogy and texture with the local bedrock; a mismatch suggests glacial transport. Petrographic analysis and geochemical fingerprinting can also help determine the block’s source.

Significance: These blocks provide important clues about past glacial processes, including ice flow directions, ice thickness, and retreat patterns. They are used in reconstructing glacial history and in teaching about ice-age geology. While many flyttblock are visible on the surface, others are partially buried and may be discovered during quarrying, construction, or field surveys.