Grand Etchings

Painterly grooves in bedrock are often evidence of the grand and orderly etchings of glacier.

Nature has a way of leaving records for the curious.

Late 18th century Swiss alpinists were the first to recognize bedrock scratches and gouges as evidence of a moving glaciers.

Glacial striation left by ice-age glaciers on a shore cliff
Otaniemi, Espoo, Finland

Many of the rock striation visible today are from receding glaciers. Striation typically occurs in multiples that run parallel to one another.

Glacial striation north of Observation Rock
Mount Rainier National Park

Rock fragments and sand grains embedded and exposed at the base of the glacier acted as abrasive etching tools. The resulting cuts align with the direction of the receding glacier.

“As long as I live, I'll hear waterfalls and birds and winds sing. I'll interpret the rocks, learn the language of flood, storm, and the avalanche. I'll acquaint myself with the glaciers and wild gardens, and get as near the heart of the world as I can".”
― John Muir

Like sandpaper, the abrasive fragments must be harder than the bedrock. Quartz can cut shale, but shale cannot cut quartz rich bedrock.

Winter is an etching, spring a watercolor, summer an oil painting and autumn a mosaic of them all.
— Stanley Horowitz

REFERENCES

• Glacial Striation, Wikipedia.
• Surface Processes and Landforms, 2nd Edition, by Don J. Easterbrook. 1999.
• Winter is an Etching: An Artistic Quotation, by Jessica Cline, Mid-Manhattan Library, Art and Picture Collections, November 15, 2011.