Wanda Denhalter, 63, was home alone on Saturday when the enormous rock crashed into her room, breaking her jaw and sternum, and leaving a huge gash on her leg.
Despite her serious injuries Mrs Denhalter was able to ring for help.
Her husband Scot, 64 had been out of town visiting the couple’s son when the accident occured and said that he was very relieved his wife wasn’t worse hurt.
“I guess she heard the rumbling as it came down the hill and woke up,” he said. “She rolled away from the oncoming noise to my side of the bed. If she had decided to swing her legs over the side of the bed and get up to investigate, it would have killed her.”
The incident occured in the hilly desert town of St George in Utah’s southwest, near the border with Arizona.
The Denhalter’s had only just moved into a rental property in the town in mid-December.
Police have said that while pieces of rock do occasionally fall onto residential areas from surrounding hills such a large boulder coming down was a completely freak event.
Sgt Marc Mortensen, a spokesperson for the town’s police force said that police were also baffled as to why the rock had fallen in the first place.
“The boulder in the hillside was in its natural state. It evidently broke loose or the soil around it somehow came loose,” he said. “In our county and in our city, we have hillsides all over the place. We’re very hilly. So this type of occurrence, while not common, it does happen from time to time.”
Mrs Denhalter has been released from hospital and is recovering well from her injuries though is more than a little lucky to be alive.
“I’m greatly relieved she’s OK,” said Mr Denhalter, in what may well be the greatest understatement of the year so far.