EMPLACEMENT OF THE 75-KM-LONG CARRIZOZO LAVA FLOW-FIELD, SOUTH-CENTRAL NEW-MEXICO

The Carrizozo Lava flow field is a young, 75-km-long, compound tube-fe d pahoehoe flow field located in south-central New Mexico. Topographic channeling, unusually low viscosity, and fissure vents are ruled out as possible explanations for the length of the flow field. Effusion ra tes are estimated using: (1) a Bingham plastic model; (2) correlations between flow morphology and effusion rate; and (3) comparison with Ha waiian pahoehoe flows. The Bingham plastic model placed no useful rest rictions on the effusion rate, while empirical and theoretical correla tions gave estimates between 300 and 3 X 10(5) m3 s-1 for the effusion rate. The striking morphological similarity of the Carrizozo flow fie ld to the compound tube-fed pahoehoe Kupaianaha flow field on Kilauea Volcano suggests an effusion rate of about 5 m3 s-1 and an eruption du ration of nearly 3 decades. This long eruption duration and a long-liv ed lava tube system are interpreted to be the most important factors r esponsible for the length of the Carrizozo flow field. Furthermore, we conclude that the Bingham plastic model does not apply to tube-fed pa hoehoe flow fields and that the correlation techniques grossly overest imate their effusion rates. This indicates that effusion rates may als o have been overestimated for extra-terrestrial lava flows where it is has not been possible to distinguish between pahoehoe and 'a'a.