▁▁ ▁The ▁la va ▁must ▁have ▁had ▁a ▁very ▁low ▁vis cos ity , ▁possibly ▁due ▁to ▁a ▁carbon at ite ▁composition . ▁At ▁the ▁vol cano ▁Ol ▁Do iny o ▁L eng ai ▁in ▁T anz ania , ▁n atro car bon at ite ▁la va ▁er u pts ▁at ▁around ▁, ▁not ▁far ▁above ▁Ven us ' s ▁mean ▁ambient ▁temperature ▁of ▁. ▁Analysis ▁of ▁cross - section al ▁profiles ▁( using ▁bright ness ▁data ▁from ▁Mag ellan ▁synth etic ▁a pert ure ▁rad ar ▁images ) ▁indicates ▁that ▁while ▁Balt is ▁Vall is ▁does ▁have ▁le ve es , ▁primarily ▁in ▁its ▁first ▁ 1 5 0 0   km , ▁and ▁int rach annel ▁rid ges , ▁mainly ▁in ▁the ▁segment ▁ 1 5 0 0 ▁to ▁ 3 0 0 0   km ▁from ▁the ▁source , ▁the ▁feature ▁is ▁primarily ▁er os ional , ▁with ▁a ▁bottom ▁surface ▁ 2 0 – 1 0 0 ▁m ▁below ▁the ▁surrounding ▁pla ins ▁at ▁ 9 0 % ▁of ▁the ▁sites ▁studied . ▁The ▁average ▁depth s ▁and ▁width s ▁of ▁the ▁channel ▁are ▁ 4 6 ▁ ± ▁ 1 6   m ▁and ▁ 2 . 2 ▁ ± ▁ 0 . 4   km , ▁respectively . ▁▁ ▁The ▁channel ▁is ▁located ▁in ▁an ▁area ▁consisting ▁entirely ▁of ▁pla ins ▁and ▁wr ink le ▁rid ges . ▁The ▁top ography ▁of ▁the ▁channel ▁und ul ates , ▁with ▁some ▁st ret ches ▁trav elling ▁u ph