What is steep walled valley created by a river or stream?

What is Tenzing Norgay's viewpoint in A Dream Comes True about being one of the first people to reach the summit of Mount Everest? What materials did people use to make bridges? What are protatoes? What were medieval cannons built from? Are there insects in the Gobi Desert? Who was the first under British throne to cross the Atlantic? How could tree roots in forest soils grow into subsoil and help a tree survive? How old are the Appalachian mountains in PA? Why is an ocean bigger than a sea? When did Liberty Seguros Continental end? Do conifer trees grow after being chopped down? What are the best beaches in St Maarten? Why does the Statue of Liberty have a flame? How did Monument Colorado get its name? What streets is walk of fame found in Hollywood? What ran along the Appalachia mountains through the far western part of the other colonial regions? Are there snakes in the Gobi desert? What is the largest prey in the sea? How has the Gobi desert changed over time? How much would it cost to build a 40 mile train track?