Final answer:
Crevasses are the name for cracks in the upper portion of a glacier, which occur due to the movement of the glacier and are an indication of its dynamic nature.
Step-by-step explanation:
The name used for cracks in the upper portion of a glacier are called crevasses. These features occur as a result of stress from the glacier moving and bending. Glacier movement can be detected by the presence of crevasses, which are significant indicators of glacial dynamics. Unlike mudcracks, which form in drying mud and are not related to glacial activity, crevasses form in the ice itself and can vary in depth and width. In Glacier National Park (GNP), glaciers are dynamic entities that undergo changes in response to temperature and precipitation levels, with their movement shaping the landscape around them through erosion.