Answer: Glaciers form when the accumulation of snow and ice in an area exceeds ABLATION.
-The sequence of glacial ice formation are snowflakes, GRANULAR SNOW, firn, glacial ice.
-Glacier cycles include; The formation of firn, accumulation of snow and ice.
-When ice and snow accumulation exceeds ablation, the glacier is said to be ADVANCING.
Explanation: Ablation is when snow and ice are removed from a snowfield. It usually occurs through MELTING and SUBLIMATION. So, when the accumulation of snow and ice exceeds ablation, it leads to glacier formation.
During glacial ice formation, it begins with the accumulation of snow and ice which leads to the formation of SNOWFLAKES through recrystallization and compaction of snow. As the snow gets buried by repeated snowfalls, snowflakes are converted to GRANULAR SNOW. Gradually, the granular snow grows larger and the air pockets reduce, causing it to become compact and denser and in turn form a FIRN. Over time, larger ice crystals are formed which is known as GLACIAL ICE through pressure melting.
Glacier formation can either be ADVANCE when the accumulation of snow and ice exceed ablation or it can RETREAT when the ice melt or ablate quickly.