On March 21, 1998, at 1200 hours Pacific standard time, a Victor Marsh, Marsh 1, N166VP, (experimental airplane) impacted trees and rising terrain about 10 miles southwest of Lone Pine, California. The airplane was substantially damaged and neither the commercial pilot nor the passenger was injured. Visual meteorological conditions prevailed, and no flight plan was filed. The personal flight originated from Lone Pine at 1100. The pilot verbally reported that he intended to fly his homebuilt airplane, with its 65 horsepower engine, in a westward direction over the Sierra Nevada Mountains. After departure from the 3,680-foot mean sea level (msl) Lone Pine Airport, he circled the area to gain altitude. Eventually the pilot located a mountain pass and proceeded in a westerly direction toward his home in Tracy, California. The pilot further reported that the elevation of the underlying terrain began increasing faster than his airplane was climbing. Unable to reverse course, he made a forced landing on the rising, snow-covered, mountainous terrain. The accident site elevation is about 10,500 feet msl and is about 8 miles southeast of Mt. Whitney. In the pilot's completed report, he indicated that at the time of the accident the wind was light and variable. There was no turbulence. The pilot also reported that no mechanical malfunctions or failures were experienced with his airplane.