Katherine Norman, who belongs to the US state of Maine, said she saw boulders the size of a bus falling towards them.
"On Saturday noon, we were starting to have lunch by the river-side when the earth just started violently shaking. Boulders the size of a bus were coming down. I really don't know how we survived," Norman told ANI.
Norman, who was accompanied by her guide, said there were people from nine countries including Israel and Netherlands.
"We were in constant terror that we will be killed by landslides, as they happened with regularity all around us," she said.
The American national pointed out that she survived by building a helicopter landing pad, and making a big "H" with red flowers to remain visible to rescuers.
"We knew there was no rescue by walking because there were some people who were not capable of doing that. The trail was covered with debris and huge boulders," she said.
"The only way out was helicopter. So we actually built a helicopter landing pad, and with red flowers made a big "H" so that we could be seen," Norman added.
Saturday's earthquake, which measured 7.9 on the Richter scale, has left an acute shortage of food, water, electricity and medicines in Nepal.
Locals in Kathmandu and other adjoining areas are spending their nights out in the open over fears of another earthquake.