Two motorcyclists were severely injured after colliding at Skyline Boulevard and Highway 84 in Woodside early Sunday afternoon, according to the California Highway Patrol.

The crash occurred at about 1:10 p.m. on state Highway 84 east of Old La Honda Road, about halfway between Skyline Boulevard and the town of La Honda, according to the CHP.

A white 2009 Ducati motorcycle driven by a 23-year-old Alameda man was traveling west on Highway 84 when, for unknown reasons, it crossed into the eastbound lane as he was approaching a 1973 green Norton motorcycle ridden by a 54-year-old San Francisco man, the CHP said.

The motorcycles collided, causing both men to be thrown from the bikes, according to the CHP.

The Alameda man suffered head trauma and was knocked unconscious, while the San Francisco man suffered a broken right leg, according to the CHP. Both men were flown by helicopter to Stanford Hospital.

All lanes were reopened on the highway by 2:10 p.m., according to the CHP.

The motorcyclists were not identified by name.

-- Bay City News Service and Palo Alto Weelkly staff