▁( as ▁well ▁as ▁ igne ous ▁pet ro log y ▁and ▁ge och em istry ) ▁util ize ▁the ▁differences ▁in ▁dens ities ▁to ▁identify ▁under pl ating ▁that ▁occurs ▁at ▁depth . ▁ ▁Ev idence ▁Mag m atic ▁under pl ating ▁has ▁been ▁identified ▁using ▁multiple ▁techniques ▁that ▁are ▁non - specific ▁to ▁the ▁area ▁in ▁which ▁they ▁are ▁used . ▁Ge och em istry ▁allows ▁ge olog ists ▁to ▁determine ▁levels ▁of ▁association ▁between ▁ igne ous ▁units : ▁in ▁the ▁Kar oo ▁Province ▁of ▁southern ▁Africa , ▁large ▁volumes ▁of ▁r hy ol ite ▁along ▁the ▁contin ental ▁margin ▁were ▁produced ▁from ▁mel ts ▁with ▁initially ▁bas alt ic ▁compos itions . ▁X en ol ith s ▁of ▁mant le ▁material ▁can ▁carry ▁information ▁about ▁the ▁ult imate ▁source ▁of ▁a ▁mag ma , ▁as ▁well ▁as ▁reve al ▁heter ogene ities ▁within ▁the ▁mag ma ▁mixing ▁and ▁assim ilation ▁of ▁host ▁mag mas ▁at ▁depth . ▁Gab bro ▁fraction ation ▁allows ▁ge olog ists ▁to ▁determine ▁the ▁smallest ▁possible ▁mass ▁of ▁conce aled ▁material . ▁Studies ▁of ▁ge omorph ology ▁in ▁the ▁Kar oo ▁Province ▁have ▁identified ▁regional ▁u pl ift , ▁associated ▁with ▁the ▁under pl ating ▁and ▁consequ ent ▁thick ening ▁of ▁the ▁cr ust . ▁ ▁Se ism ic ▁studies ▁of ▁the ▁cr ust ▁at ▁depth ▁have ▁done ▁a ▁great ▁deal ▁to ▁identify ▁mag m atic ▁under pl ating , ▁but ▁without ▁direct ▁samples ▁to ▁look ▁at , ▁it ▁can ▁be ▁problem atic ▁for ▁ge