▁The ▁cr ust al ▁port ions ▁of ▁ocean ic ▁t ect onic ▁pl ates ▁are ▁composed ▁pre domin antly ▁of ▁bas alt , ▁produced ▁from ▁up well ing ▁mant le ▁below , ▁the ▁ocean ▁rid ges . ▁ ▁Bas alt ▁is ▁one ▁of ▁the ▁most ▁common ▁rock ▁types ▁in ▁the ▁world . ▁Bas alt ▁is ▁the ▁rock ▁most ▁typical ▁of ▁large ▁ igne ous ▁provinces . ▁The ▁largest ▁occurr ences ▁of ▁bas alt ▁are ▁in ▁the ▁ocean ▁floor ▁that ▁is ▁almost ▁completely ▁made ▁up ▁by ▁bas alt . ▁A bove ▁sea ▁level ▁bas alt ▁is ▁common ▁in ▁hot spot ▁islands ▁and ▁around ▁vol can ic ▁ar cs , ▁spe cially ▁those ▁on ▁thin ▁cr ust . ▁However , ▁the ▁largest ▁volumes ▁of ▁bas alt ▁on ▁land ▁correspond ▁to ▁contin ental ▁flo od ▁bas al ts . ▁Cont inental ▁flo od ▁bas al ts ▁are ▁known ▁to ▁exist ▁in ▁the ▁De cc an ▁Tra ps ▁in ▁India , ▁the ▁Ch il cot in ▁Group ▁in ▁British ▁Columbia , ▁Canada , ▁the ▁Par an á ▁Tra ps ▁in ▁Brazil , ▁the ▁Si ber ian ▁Tra ps ▁in ▁Russia , ▁the ▁Kar oo ▁flo od ▁bas alt ▁province ▁in ▁South ▁Africa , ▁the ▁Columbia ▁River ▁Pl ate au ▁of ▁Washington ▁and ▁Oregon . ▁ ▁Many ▁arch ip el ago es ▁and ▁island ▁nations ▁have ▁an ▁over wh el ming ▁majority ▁of ▁their ▁exposed ▁bed rock ▁made ▁up ▁of ▁bas alt ▁due ▁to ▁being ▁above ▁hot sp ots , ▁for ▁example , ▁I cel and ▁and ▁Hawai