Ice Versus Rock

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This enormous glacier flows down a mountainside like a river of ice. Blocked by a large rock outcrop it flows around, making a greater than 90 degree turn. In doing so it grinds against the obstacle with rocks that are carried within the ice. Some of these rocks are enormous and some are finer than sand. This very slow but steady grinding pulverizes the carried rocks and the obstacle into progressively smaller pieces, some of which become a fine flour like dust that is called "glacial flour. Glacial flower particles are so fine they can be suspended in the glacier's melt water, coloring it an iridescent green-blue.