y ng en etic ▁Anti - s y ng en etic ▁ice ▁w edge ▁were ▁first ▁observed ▁in ▁ 1 9 9 0 ▁during ▁the ▁field work ▁of ▁J . ▁Ross ▁Mack ay . ▁Mack ay ▁found ▁that ▁anti - s y ng en etic ▁grew ▁in ▁conditions ▁opposite ▁to ▁those ▁of ▁sy ng en etic ▁ice ▁wed ges ▁in ▁that ▁the ▁anti - s y ng en etic ▁variety ▁required ▁the ▁removal ▁of ▁material ▁instead ▁of ▁the ▁accum ulation ▁and ▁addition ▁of ▁material . ▁Anti - s y ng en etic ▁ice ▁wed ges ▁only ▁form ▁on ▁s lop es , ▁where ▁there ▁is ▁a ▁net ▁loss ▁of ▁materials ▁er os ion . ▁Similar ▁to ▁sy ng en etic ▁ice ▁wed ges , ▁anti - s y ng en etic ▁ice ▁wed ges ▁can ▁only ▁occur ▁if ▁the ▁rate ▁of ▁thermal ▁contra ction ▁crack ing ▁and ▁ice - ve in let ▁growth ▁keeps ▁pace ▁with ▁the ▁removal ▁of ▁active ▁material . ▁Anti - s y ng en etic ▁ice ▁wed ges ▁therefore ▁only ▁grow ▁down wards , ▁pen etr ating ▁deeper ▁into ▁the ▁soil ▁only ▁as ▁the ▁upper ▁layers ▁are ▁removed ▁by ▁mass ▁was ting ▁and ▁er os ion . ▁In ▁an ▁anti - s y ng en etic ▁ice ▁w edge , ▁the ▁age ▁of ▁the ▁ice ▁on ▁the ▁peri ph ery ▁increases ▁up wards . ▁ ▁References ▁ ▁Category : Per ig la cial ▁land forms ▁Category : Pattern ed ▁grounds ▁Category : Per ma f rost <0x0A> </s> ▁Z