The couple are believed to have been scouting out the ascent from a trail at the base of the El Capitan rock formation when a sheet of granite, about 40 metres by 20 metres, broke free and fell from 1,800ft above the valley floor.
The rockfall is significantly larger than yesterday's, says Yosemite spokesman Scott Gediman. There's no word on his condition.
The first slab fell from a peak at the world-class climbing destination El Capitan on Wednesday afternoon, followed by a much larger chunk of granite from the same section of the mountainside Thursday afternoon.
An adventure tour guide who has led hikers in Yosemite Park for 12 years says the big rock fall that killed at least one person and injured another at the iconic El Capitan rock formation was the biggest slide he's ever seen at the park. "Well basically a natural process, Rockfall is one of those things that makes it one of the many kinds of landslides we have to be aware of to keep ourselves safe", said Jerry De Graff, Fresno State Geology Professor.
Rocks at the world-renowned park's climbing routes break loose and crash down about 80 times a year. That creates more cracks and causes the rock to become more unstable, Verdoorn said. He dived on top of me as soon as he could see what was going to happen.
On Wednesday, a climber from Wales was killed and his wife seriously injured. Park officials say rock falls overall have killed 16 people since 1857 and injured more than 100.
Yosemite National Park identified the man Thursday as Andrew Foster, 32.
The park indicated that seven rock falls actually occurred during a four-hour period Wednesday on the southeast face of El Capitan.
Andrew Foster and his wife Lucy were nearing the end of a three-week trip to the California park and sizing up their toughest hike yet on the El Capitan monolith when Andrew was crushed to death Wednesday.
"That part of [El Capitan] is pretty unconsolidated, but the west part of El Cap is so solid that nothing is likely to come off".
The two were climbing in the park during the incident. Californian Chris Koenig said he visits Yosemite a lot.