Answer to Question 1
Answer: An accumulation of snow and ice that is thick enough to flow under its own weight.
Answer to Question 2
Answer: The desert valleys were deep, freshwater lakes. The distribution of ice-age lakes in the Great Basin tells us that the climate was much wetter 20,000 years ago. We reconstruct ancient climate by finding records of past vegetation. The preserved nests of packrats provide a record of vegetation history, because packrats collect sticks and brush into dense artificial thickets. Northern Mexico
