96%(425)407 out of 425 people found this document helpful
This preview shows page 254 - 256 out of 972 pages.
and jumping up-and-down vigorously. Predictably, the tourist said "of course not, it might fall over." Dr. Alley then pointed out the many places where rocks clearly had fallen off the cliffs and moved downhill, at which point the tourist quickly switched his opinion to the "down-cutting" river explanation, with the ranger thoroughly enjoying the show. Points Earned:1/1 Your Response:D 14.Sam Ascah is standing on sand and gravel in a pothole, where a stream swirls during the short but intense thunderstorms of Zion National Park. And next to that stream, the other picture shows the sandstone and the hang-on-so-you-don’t-fall-over-the-cliff chain along the trail. A likely interpretation of these features is: The Park Service carefully cut little grooves behind the chain before they hung it, so that it would look cute and slide well, and they cut the potholes so that hikers would have something to look at. A.The potholes and the grooves behind the chain were gnawed by giant marmots. B.The grooves behind the chain have been cut over decades by motion of the chain as hikers grabbed it, and the potholes were cut by water swirling rocks around during the rare floods over much longer times. C.The stream swirled rocks around and cut the potholes, and even bounced up the cliff to cut the notches behind the chain. D.The potholes and the grooves behind the chain were gnawed by giant beavers. E.