POINT REYES NATIONAL SEASHORE (CBS SF) — A popular hiking trail in Point Reyes National Seashore will likely never be repaired after the ground gave way Saturday, sending two hikers tumbling 70-feet, leaving one dead.

Park crews posted warning signs for hikers that the Bear Valley Trail was still open, but the Arch Rock lookout popular with tourists was off-limits.

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“It’s very unstable.  It falls apart all the time,” park spokesperson John Dell’Osso said.

One San Francisco woman was killed, and a second left in serious condition when a portion of Arch Rock, a well-known bridge carved by Mother Nature caved in, sending the two hikers falling 70-feet.

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“You can see a crack going through the dirt.  We didn’t step over that at all.  We stepped back after seeing the signs there had been a collapse,” hiker Sarah Merkel said.

Dell’Osso said it’s likely Arch Rock itself will never be repaired.

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“We have had serious waves that have taken people off the beaches and pulled them out, but I have never seen something where the ground has just collapsed beneath someone’s feet,” Dell’Osso said.