les ▁a ▁desert ▁because ▁of ▁its ▁location ▁on ▁the ▁vol can ic ▁plate au ▁adj ac ently ▁east ▁of ▁R ua pe hu , ▁a ▁poor ▁soil ▁quality ▁and ▁dry ing ▁wind s , ▁and ▁also ▁due ▁to ▁the ▁mass ▁ster il isation ▁of ▁se eds ▁during ▁a ▁series ▁of ▁violent ▁er u ptions , ▁particularly ▁ign im br ite ▁flows ▁about ▁ 2 0 , 0 0 0 ▁years ▁ago . ▁The ▁veget ation ▁is ▁low ▁and ▁sparse , ▁consisting ▁of ▁mainly ▁t us sock ▁and ▁snow ▁grass es . ▁The ▁head w aters ▁of ▁many ▁small ▁streams , ▁which ▁later ▁turn ▁into ▁large ▁rivers , ▁g ou ge ▁deep ▁ser r ated ▁valle ys ▁through ▁the ▁un con sol id ated ▁ash ▁and ▁p um ice - rich ▁earth . ▁The ▁climate ▁here ▁is ▁har sh ▁and ▁al pine , ▁with ▁close ▁to ▁ 2 7 0 ▁ground ▁fro st s ▁per ▁year ▁in ▁comparison ▁with ▁less ▁than ▁ 3 0 ▁in ▁the ▁coast al ▁regions ▁of ▁Haw ke ' s ▁Bay , ▁ ▁to ▁the ▁east . ▁He avy ▁snow falls ▁- ▁rarely ▁seen ▁in ▁the ▁rest ▁of ▁the ▁island ▁- ▁are ▁also ▁a ▁common ▁occurrence ▁in ▁winter . ▁Tr amp ers ▁and ▁clim bers ▁in ▁the ▁area ▁should ▁be ▁mind ful ▁of ▁the ▁extreme ▁ch ill ▁effect ▁of ▁the ▁cold ▁south ▁wind ▁which ▁can ▁produce ▁wind ▁ch ill ▁factors ▁lower ing ▁the ▁temperature ▁below ▁ 0 ° c ▁( 3 2 ° F ) ▁for ▁days ▁on ▁end .