aki ▁f iss ure ▁are ▁very ▁near ▁from ▁each ▁other , ▁la va ▁from ▁the ▁Kat la ▁and ▁the ▁He k la ▁vol can ic ▁systems ▁result ▁in ▁trans itional ▁al kal ic ▁bas al ts ▁and ▁la va ▁from ▁the ▁central ▁vol cano es ▁result ▁in ▁th ole i it ic ▁bas al ts . ▁The ▁central ▁vol cano ▁of ▁B ár ð ar b ung a , ▁the ▁Ve id iv ö tn ▁and ▁T roll ag ig ar ▁f iss ures ▁form ▁one ▁vol can ic ▁system , ▁which ▁extend ▁about ▁ 1 0 0   km ▁SW ▁to ▁near ▁Tor f aj ök ull ▁vol cano ▁and ▁ 5 0   km ▁NE ▁to ▁near ▁Ask ja ▁vol cano , ▁respectively . ▁The ▁sub g la cial ▁L oki - F ög ruf jö ll ▁vol can ic ▁system ▁located ▁SW ▁of ▁B ár ð ar b ung a ▁vol cano ▁is ▁also ▁part ▁of ▁the ▁B ár ð ar b ung a ▁vol can ic ▁system ▁and ▁contains ▁two ▁sub g la cial ▁rid ges ▁extending ▁from ▁the ▁largely ▁sub g la cial ▁Ham ar inn ▁central ▁vol cano ▁( 1 5   km ▁south west ▁of ▁B ár ð ar b ung a ); ▁the ▁L oki ▁r idge ▁tr ends ▁to ▁the ▁NE ▁and ▁the ▁F ög ruf jö ll ▁r idge ▁to ▁the ▁SW . ▁New ▁Zealand , ▁North ▁Island , ▁T au po ▁Vol can ic ▁Zone : ▁The ▁following ▁Vol can ic ▁Cent