Answer to Question 1
The glacial budget is dependent on the zone of accumulation and the zone of wastage. The glacial budget refers to a balance (or lack of balance) between these two zones. If accumulation exceeds wastage, there is a positive budget, and the ice advances. If wastage exceeds accumulation, there is a negative budget, and the ice retreats.
Answer to Question 2
Crevasses are huge cracks in the brittle upper 50 meters of glacial ice. When the ice mass moves over irregular terrain, the brittle part of the ice, the zone of fracture, is subjected to tension, resulting in cracks.