rock flour

American  

noun

1. glacial meal.

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rock flour British  

noun

1. very finely powdered rock, produced when rocks are ground together (as along the faces of a moving fault or during the motion of glaciers) and are thus chemically unweathered

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Etymology

Origin of rock flour

First recorded in 1880–85

Example Sentences

Near the surface, rocks are involved in repeated brittle faulting produce a material called rock flour, which is rock ground up to the particle size of flour used for food.

From Textbooks • Jan. 1, 2017

In addition, rock flour as fine grit in the ice can polish a hard granite or quartzite bedrock to a smooth surface called glacial polish.

From Textbooks • Jan. 1, 2017

Many glacial tills, glacially derived diamictites, include very finely-pulverized rock flour along with giant erratic boulders.

From Textbooks • Jan. 1, 2017

Together, the movement plucks off bedrock and grinds the bedrock producing a polished surface and fine sediment called rock flour as well as other poorly-sorted sediments.

From Textbooks • Jan. 1, 2017

The product of plucking is bowlders, while the product of abrasion is fine rock flour and sand.

From The Elements of Geology by Norton, William Harmon