Document Type

Honors Project On-Campus Access Only

Abstract

In the far north of Iceland, the nine Krafla Fires of 1975 to 1984 produced large volumes of basaltic lava primarily by fissure fed eruptions, which created a variety of volcanic features. Bulbous squeeze-ups, an unusual and previously undescribed lava flow feature, were discovered during a 2015 field study of an inflated flow field formed during the September 1984 eruption at Krafla. Field studies indicate bulbous squeeze-ups form only on linear pull-apart features, and are likely of high viscosity upon extrusion. The jumbled nature of the flow field surrounding these bulbous squeeze-ups suggests a pulsed, somewhat violent, and rapid emplacement and cooling history. Geochemical and petrographic investigations indicate that bulbous squeeze-ups, elongate squeeze-ups, and pahoehoe plates from the northern flow field are texturally and chemically indistinguishable (e.g., Cohen’s d < 2 for whole rock major and trace element comparisons) suggesting that these features formed from a single, homogenous and unfractionated magma. Principal component analysis (PCA) of major and trace element concentrations further supports this interpretation. The lack of literature describing similar squeeze-up morphologies suggest that the factors that controlled the formation of bulbous squeeze-ups in the northern flow field are somewhat unique to Krafla. Specifically, the formation of bulbous squeeze-ups are largely controlled by pulsed inflation, low slope, high effusion rate, and high viscosity upon extrusion. Importantly, if the manner in which bulbous squeeze-ups form is determined, the identification of this distinctive morphology could be telling of conditions of past eruptions on earth, as well as on other planets with observable lava flows.

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