On May 11, 2002, at approximately 1220 mountain daylight time, a Piper PA-28-140B, N345M, was substantially damaged following impact with terrain subsequent to an inadvertent stall/mush at Monument Valley Airport, Monument Valley, Utah. The private pilot and his passenger were not injured. The pilot was operating the airplane under Title 14 CFR Part 91. Visual meteorological conditions prevailed for the cross-country flight that originated from Chandler Municipal Airport, Chandler, Arizona, at 1013. The pilot had not filed a flight plan. The pilot said that he researched the airport before his flight. He was aware of the normal procedures regarding carrying more airspeed and placing the aircraft "firmly" on the runway. He arrived at the destination 2-3 hours after the planned arrival time. At approximately 50 feet above ground level, the airplane experienced a significant loss in air speed due to a "sudden wind shift/shear." The aircraft was moved approximately 50 feet to the right and impacted an earth berm. The nose wheel landing gear collapsed aft, and the engine mount, engine firewall, cowling and fuselage were bent.