This material's deep layers are home to solid formations called depth hoares that can cause structural weakness in formations of it. At high altitudes, this material can form spike-like objects known as penitentes. When it is denser than 550 kilograms per cubic meter, this material is known as firn, and its compacted, resolidified form is called n??and formed via nivation. The calculation of mass balance compares the accumulation of this material to the rate of ablation; a positive measure indicates glaciation. For 10 points, name this form of 
This material's deep layers are home to solid formations called depth hoares that can cause structural weakness in formations of it. At high altitudes, this material can form spike-like objects known as penitentes. When it is denser than 550 kilograms per cubic meter, this material is known as firn, and its compacted, resolidified form is called n??and formed via nivation. The calculation of mass balance compares the accumulation of this material to the rate of ablation; a positive measure indicates glaciation. For 10 points, name this form of solid precipitation that generally falls in white flakes during the winter.
This material's deep layers are home to solid formations called depth hoares that can cause structural weakness in formations of it.
snow [do not accept "ice"]