Boulder Park

Boulder Park National Natural Landmark, of Douglas County, Washington, along with the nearby McNeil Canyon Haystack Rocks and Sims Corner Eskers and Kames natural landmarks, illustrate well-preserved examples of classic Pleistocene ice stagnation landforms that are found in Washington.

Boulder Park and adjacent areas is covered by a discontinuous blanket of gravelly, sandy loam glacial till.

It was cut by older Spokane Floods at a time prior to when the Okanogan ice lobe partially covered the Waterville Plateau during most of the last of the Last Glacial Maximum.

[2][4][5] Underlying the glacial deposits of the Okanogan ice lobe and outcropping, where it is absent, is the middle Miocene, Priest Rapids Member of the Wanapum Basalt.

It forms a large igneous province that covers an area of 163,700 km2 (63,000 mile2) of the Pacific Northwest with an estimated volume of 174,300 km3 of basalt lava and other volcanics.