The crash happened at about 8:45 a.m. on southbound Interstate Highway 680 just north of Bollinger Canyon Road, California Highway Patrol Officer Steve Creel said.
A 2004 Chrysler Pacifica was traveling in the far right lane at about 50 to 55 mph when a 2003 Chevrolet Impala traveling in the next lane over came up from behind at about 65 mph, Creel said.
A witness reportedly saw the Chevrolet cross into far right lane and strike the rear of the Chrysler, Creel said.
The impact caused both vehicles to veer right, drive off the road and down a slope.
The right side of the Chevrolet struck a tree on its way down the embankment. Both vehicles continued down the slope and came to rest on a concrete drainage strip with the Chrysler on top of the overturned Chevrolet. Hill, the right front passenger of the Chevrolet, was pronounced dead at the scene.
The driver of the Chevrolet, 52-year-old Palo Alto resident Alpha Anderson, sustained minor injuries.
The two people in the Chrysler, a 75-year-old man and a 63-year-old woman, both San Ramon residents, also sustained minor injuries, Creel said.
The cause of the crash remains under investigation, but initial reports did not indicate that drugs or alcohol were involved.