See the context of this sign.

Siege of Ice

Only ice, sky and a few jagged islands of rock - an ocean of ice
filled the horizon.

If there is valley fog, imagine it is ice, and you will have a picture
of the continental glacier, grinding against the terrain.

Glaciers were the prime architects of the scenery before you. But
in this green landscape the only way to comprehend the extant
of the ice is to examine the aftermath. A thousand feet above this
spot the melting glacier dumped tons of rock and gravel debris.
Only glaciers could have carved this valley's steep walls.

House-sized boulders lie scattered
around the park, their crystals
foreign to Olympic rock.

Don't miss the rest of our virtual tour of Olympic Mountains National Park in 646 images.