Ubhedu luvela kumanzi omdaka, ubukhulu becala babunjwe ngamanzi, kwaye kukhutshwa yiMagma epholileyo. Le magma, esisisiseko sokuqhushumba, ivela kuMalayini ephakathi phakathi kweyona nto iphambili emhlabeni kunye ne-crust, oko kukuthi, ingubo, kwaye ke inyukele kumhlaba we-magma ukuba ibe yigumbi le-magma. Ubunzulu beli gumbi luhlala luphakathi kwe-5km kunye ne-15km.

Ukuqulunqwa kweediphozithi zobhedu kuthatha amashumi amashumi amawaka ukuya kumakhulu amawaka eminyaka, kunye nokuqhushumba kwentaba-mlilo kuqhume rhoqo. Ukuqhushumba okusilela kuxhomekeka kwindibaniselwano yeeparamitha ezininzi Inqanaba le-magma, umyinge wokupholisa kunye nobunzima be-purts ejikeleze igumbi le-magma.

Ukufunyanwa kokufana phakathi kokuqhuma kwentaba-mlilo yentaba-mlilo kunye ne-sediments kuya kwenza ukuba kusetyenziswe ulwazi olukhulu olufunyenwe ziintaba-mlilo ukuqhubela phambili ukuqonda kwabantu ngoku.