"A glacial ‘erratic’ is a rock fragment carried by glacial ice and transported some distance from the outcrop from which it was derived, and generally resting on bedrock of a different type* [although glacial or alluvial sediment may directly underlie the erratic. " (source: NW Geology)
Many erratic boulders line the shores of Puget Sound. Some large erratics can be found in Seattle such as 4 Mile Rock off the south side of Magnolia and this one below off North Beach of Discovery Park. Read more about erratic boulders (source: NW Geology)
Possibly the most interesting erratic is Haleelts Rock on the north end of Bainbridge Island which has a petroglyph on it's north facing side. See pic below.
|Haleelts Rock, Bainbridge Island|
|4 Mile Rock|
|Discovery Park erratic, North Beach|
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