The couple, who were found with climbing equipment, are thought to have been scouting the ascent from a trail when a sheet of granite around 40 metres by 20 metres (131ft by 65ft) fell from a height of around 200 metres 650ft.
Another set of climbers watched both rockfalls go down on the "Waterfall Route", located on what is known as the East Buttress of El Capitan.
Stock said park officials would not allow people into any area they felt is unsafe.
Climbers are aware of the risks of the sport and that granite erosion takes place on El Capitan and other peaks in the Sierra Nevada mountain range, he said.
Rocks at the world-renowned park's climbing routes break loose and crash down about 80 times a year.
A man injured when a second massive rock fall plunged in Yosemite was driving out of the park when rock and rubble broke through the sunroof of his SUV and a rock hit him in the head, his wife said.
"It's kind of an inherently risky sport", Hayden Jamieson, 24, of Mammoth Lakes, Calif., said Friday, as he prepared to head up the nose of El Capitan early today with his climbing partner.
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The two sat together and took in a match of the wheelchair tennis between Australia and New Zealand at the small venue. They discussed the games, their families and ribbed each other about which team would come out ahead, Grisham said.
Lucy Foster was airlifted to a hospital and was reportedly in critical condition.
His wife, Rachel Evans, told KSEE-TV of Fresno that the family had just finished a three-day visit to Yosemite. Triggering mechanisms like water, ice, earthquakes, fluctuation in temperature, and vegetation growth are among the final forces that cause unstable rocks to fall.
"We were trying to outrun it".
"Mother Earth changes every day, and we just have to get used to it, I guess", he said.
"We are a young married couple who enjoy nothing more than getting out and having adventures in the mountains together", it reads.
According to an NBC News report, Thursday's rockfall was much larger than the series of falls that came down Wednesday that killed one Welsh tourist and seriously injured his wife.
At least 30 climbers were on the vertical wall of the 7,569-foot (2,307 meter) El Capitan when the huge rock hunk fell Wednesday afternoon.