 Ubushushu bayo abufani njengemiqolomba emikhulu eMhlabeni ehlala igcina ubushushu obungagungqiyo, kodwa iyahambelana nale meko yokuba yimingxunya enzulu emhlabeni, utshilo uGlen Cushing wese United States Geological Survey USGS IQela le-Astrogeology yaseMelika kunye neYunivesithi yase-Arizona eseFlagstaff, eArizona. 