Hekla Volcano, Iceland, in the 20th Century: Lava Volumes, Production Rates, and Effusion Rates

Lava flow thicknesses, volumes, and effusion rates provide essential information for understanding the behavior of eruptions and their associated deformation signals. Preeruption and posteruption elevation models were generated from historical stereo photographs to produce the lava flow thickness maps for the last five eruptions at Hekla volcano, Iceland. These results provide precise estimation of lava bulk volumes: V_1947–1948 = 0.742 ± 0.138 km³, V₁₉₇₀ = 0.205 ± 0.012 km³, V_1980–1981 = 0.169 ± 0.016 km³, V₁₉₉₁ = 0.241 ± 0.019 km³, and V₂₀₀₀ = 0.095 ± 0.005 km³ and reveal variable production rate through the 20th century. These new volumes improve the linear correlation between erupted volume and coeruption tilt change, indicating that tilt may be used to determine eruption volume. During eruptions the active vents migrate 325–480 m downhill, suggesting rough excess pressures of 8–12 MPa and that the gradient of this excess pressure increases from 0.4 to 11 Pa s⁻¹ during the 20th century. We suggest that this is related to increased resistance along the eruptive conduit.