Our experience of slope is all off. Hiking up trails that seem steep to us we imagine the slope is 30% or some such, when really it was almost certainly less than 10%. We gaze up at the mountains and imagine them looming above us. Mostly they don't. There are steep places, of course, but on the broad scale the world is really pretty flat. To give any indication of the landscape's ups and downs, profile maps employ "vertical exaggeration", making each inch of the vertical scale represent much more distance than the horizontal scale. Above is a profile of Hawaii's big island, showing the actual slope of this mountain as it rises from the sea floor to the peak of Mauna Kea.
And here is the actual slope of the "Marianas Trench", down which James Cameron just descended to the deepest part of the ocean. Not much of a canyon, is it? These are from a cool graphic of the ocean you can see here.