Arch Rock at Point Reyes collapses into the sea, taking a couple of hikers with it.

Disaster struck two hikers walking along Bear Valley Trail in Marin County, California, towards the popular Arch Rock overlook, when the cliff gave way over the arch and they fell some 60 feet onto the beach below.

One of the hikers was pronounced dead at the scene and the other was airlifted to Santa Rosa Memorial Hospital, he said.

Park officials had put up signs at the trailhead Wednesday warning that visitors should not hike out to the end of Bear Valley Trail because a fissure had appeared at the "tip" of the overlook, a Park Service spokesman said.

Having hiked at Point Reyes many times, I can tell you from personal experience that the cliffs and land there is very obviously crumbly and unstable.  Still, in the before pictures, the rock over the arch looks quite substantial, so I suppose one could understand how the risk of collapse could be underestimated. 

The arch before the collapse.  This is classic central California coastal scenery, and no doubt a great place to whale watch during migration season.

The seaward side of the arch.

The aftermath.  Looks like a substantial slide.