Grand Coulee Dam to Dry Falls

Crown Point Vista, Haystack Rocks and Lakebeds

[152.4 MM 27]
After returning up the hill to Coulee Dam we turn right at the junction of Highway 155 and Highway 174 West. This takes us to Crown Point Vista.

[155.5 MM 21 174W]
Massive Grand Coulee Dam fills the channel. The powerhouse on the left were added after initial construction. The spillways are to the right between the two original powerhouses. We head back up Crown Point Vista road and turn right onto Highway 174.

Massive Grand Coulee Dam fills the channel.

[158.4 MM 24]
Known as the Waterville Plateau, this area was glaciated by the Okanogan lobe of an ice sheet covering western Canada and upper Washington State.

Watch for glacial tills, eskers, moraines and erratic rocks left behind by the melting glacier.

In this NASA image (right) there are black erratic boulders found in the Nylosyrtis-Mensae area of Mars. Scientists are unsure of what brought them there. Rocks that seem to be out of place because they are made from different materials are called Erratics.

[163.2 MM 13]
These huge boulders are known as haystack rocks. Both sides of the road are fields that contain these erratics as seen in these photos. Click here for a close up of one of these scoured rocks transported by a glacier. Note the size of the erratic rock (in the close up view) compared to the 4 foot tall fence post. Looking to the west are the foothills of the Cascade Mountains and to the north are the mountains of the Colville National Forest.

These huge boulders are known as haystack rocks. Click here for a close up of one.

Geology Terms

Here are some basic terms used on this page. Find more geology terms in the Glossary.

Basalt

Volcanic rock caused by partial melting of the Earth's crust.

Erratic

Large rock or boulder carried by water or glaciers and left behind.

Esker

A narrow, winding ridge made of gravel usually formed by streams flowing on a glacier or in a tunnel below the glacier or ice sheet.

Moraine

Deposits of rocks, boulders, gravel and sand (called glacial drift) left behind by glaciers as they melted. Terminal moraines are at the end of a glacier.

Outwash

Deposits of rocks, boulders, gravel and sand (called glacial drift) left behind by flowing water from glaciers as they melted.

Outwash Plain

A smooth plain covered by deposits from water flowing from glaciers.

Sediment

Collection of sand, silt, gravel and organic material that sinks to the bottom of a river, lake or ocean. Some or all of these materials may be present.

Sedimentary Rock

Rock formed by pressure and accumulation, e.g., lakebeds changed into rock form loose sand, silt and organic materials.

Till

Deposit from a glacier of unsorted rocks, boulders, gravel and sand (glacial drift).

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