Mima Mounds Natural Area Preserve is located about 12 miles (21 Km) southwest of Olympia, Washington. The mounds are composed of unlayered soil 6 to 7 feet (1 to 2 meters) high and about 30 feet (9 meters) apart. There are two prevailing theories on their formation. One is that just after the last ice ages (about 10,000 years ago) pocket gophers (which are no longer present in the valley) built the mounds since they were unable to burrow through the underlying gravel. The other involves the deposition of wind-blown silt, trapped in the glaciers that covered the valley, as the glaciers melted. The deposit then developed large-scale polygonal cracks from the subsequent freezing-thawing cycle, and eventually eroded into the regularly-spaced mounds.
A little side note: moments before this photo was taken, a magnitude 5.5 earthquake, the largest in the region in 30 Years (circa 1999), rattled the area.
Print No. A99NW-13-4
Beacon Rock
Beacon Rock State Park lies on the north side of the Columbia River Gorge, 35 miles (58 Km) east of Vancouver, Washington. At 848 feet (259 meters) high, Beacon Rock is the world's second largest monolith next to the Rock of Gibraltar. It is the eroded neck (central vent) of a basaltic andesite volcano. The Columbia River Gorge is in the background.
Print No. A99NW-16-1
The story behind Dry Falls began in the late Miocene and early Pliocene Epochs, when massive flows of the Columbia River Basalt covered much of the Pacific Northwest. The lava flows were subsequently tilted and warped. Then during the Pleistocene Epoch, a series of ice sheets moved south out of Canada. These lobes of ice, up to one mile thick in some areas, created natural dams, forming huge lakes in Washington, Idaho, and Montana. Then between 10,000 and 15,000 years ago, a series of massive floods occurred as the lakes in western Montana breached the ice dams. These floods created the Channeled Scablands of eastern Washington, and formed the massive falls here. When it was active, Dry Falls was 3.5 miles (5.6 km) long and dropped 400 feet (120 meters). By comparison, Niagara Falls is only 1 mile (1.6 km) wide and falls 165 feet (50 meters).
Print No. A01NW-20-2
The Grand Coulee Dam was built in 1933 to 1942. It is 550 feet (168 meters) high and 4,173 feet (1,272 meters) long. It spans the Columbia River northwest of Spokane. A coulee is a dry or intermittent stream valley, particularly a long trench-like gorge that once carried meltwater from an icesheet. The Grand Coulee Dam lies at the junction where the Columbia River diverges from the massive Upper Grand Coulee. The Upper Grand Coulee is where the floods that formed Dry Falls (downstream, in the Lower Grand Coulee) resulted in falls up to 800 feet (245 meters) high. The floodwater undercut the Columbia River Basalt (seen as the plateau-forming cliffs in this image) as the falls retreated 20 miles (32 Km) upstream to near the location of the Grand Coulee Dam.
Print No. A01NW-19-11
