Ubhedu luvela kulwelo olushushu, ikakhulu oluqulunqwe ngamanzi, kwaye lukhutshwa yimagma epholileyo.Ezi magma, ekwasisiseko sogqabhuko-dubulo, ziphuma kumbindi ophakathi kombindi womhlaba kunye noqweqwe, oko kukuthi, i-mantle, zize zinyuke ziye kumphezulu womhlaba ukuze zenze igumbi lemagma.Ubunzulu beli gumbi buphakathi kwe-5km kunye ne-15km.

Ukwenziwa kweediphozithi zobhedu kuthatha amashumi amawaka ukuya kumakhulu amawaka eminyaka, kwaye ugqabhuko-dubulo lwentaba-mlilo luxhaphakile.ugqabhuko-dubulo olungaphumeleliyo luxhomekeke kwindibaniselwano yeeparamitha ezininzi izinga lenaliti ye-magma, isantya sokupholisa kunye nokuqina koqweqwe olujikeleze igumbi le-magma.

Ukufunyanwa kokufana phakathi kogqabhuko-dubulo olukhulu lwentaba-mlilo kunye nentlenga kuya kwenza kube lula ukusebenzisa ulwazi oluninzi olufunyenwe ziingcali zentaba-mlilo ukuqhubela phambili ukuqonda kwangoku kokusekwa kweentlenga ze-porphyry.