Marcus Cook, who is from Salisbury, was lying 20ft (6m) up on some shingle at Frenchman's Pinnacle for two hours.
Thirteen members of Avon and Somerset Search and Rescue team were called to the scene after receiving an emergency call at 0850 GMT.
Paramedics believe he has a broken elbow and may need surgery. He was taken to Weston-super-Mare's hospital.
His friend said they were walking along landslip quarry when Mr Cook slipped past him and began to roll down the mountain.
Ben Tresham said: "It was quite possibly one of the most frightening things that has every happened in my life."
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