Big Four is a mountain in the Cascade Range, located about 20 miles (32 km) east of Granite Falls, Washington. Debris piles on the mountain's northern flank form as a result of avalanche activity. These fields of disturbed snow are able to remain year round in the shadow of the mountain. During the summer months snow-melt streams flow beneath the debris piles and cause caves to form in the ice. The caves vary in size from season to season and are unpredictably dangerous.