Persistent grain types are typically found in the snowpack up to what depth?

• A. 2 meters
• B. 3 meters
• C. 1 meter
• D. 0.5 meter

Answer: (C)

Persistent grain types form from metamorphism driven by a strong vertical temperature gradient in the snowpack. These grains—such as facets and depth hoar—reappear and persist as the snow evolves, especially in the upper portion of the layers where warming and cooling cycles are active. This metamorphism tends to dominate the snowpack down to about a meter, so persistent grain types are typically found up to roughly 1 meter depth. Beyond that depth, pressure metamorphism and more isothermal conditions reduce the formation and persistence of those grain forms.