10/15/2026
Why are Lake McDonaldโs rocks so colorful? ๐๏ธ
The answer starts with iron. When iron in the ancient sediments reacted with oxygen, it created the red shades seen along the shore, much like rust. Green rocks formed under conditions with little oxygen, eventually developing a green mineral called chlorite.
Those colorful pebbles hold clues to Glacierโs past, long before these mountains formed.