Virtually all the rock you see is basalt. The lakes and all but the pics of Marlin Hollow and Upper Irby Road are old craters which spewed molten lava eons ago. Other formations were caused by the upeavals from earth movement or quakes or basalt exposed by rushing waters from gigantic floods.
It's very beautiful country this time of year when the rains have made everything so green. The lakes are part of a chain that runs from a point about 40 miles east of Coulee City to where Crab Creek runs into Brooks Lake near Stratford, WA. In recent years, deep well irrigation and dry weather has caused some of the lakes in the chain to disappear from sight. There is a proposal before the Bonneville Administration to re-hydrate the chain of lakes for irrigation purposes, from Banks Lake (water reserved from the Grand Coulee Dam).
With all the rain we've had, "million dollar rain", as the wheat ranchers call it, even the sage brush looks elegant!