Morphology and dynamics of explosive vents through cohesive rock formations. Issue 6 (26th June 2014)

• Record Type: Journal Article
• Authors: Galland, O.; Gisler, G. R.; Haug, Ø. T.
• Is Part Of: Journal of geophysical research. Volume 119:Issue 6(2014:Jun.)
• Page Start: 4708
• Page End: 4728
• Publication Date: 2014-06-26
• Subjects: Geomagnetism -- Periodicals; Geochemistry -- Periodicals; Geophysics -- Periodicals; Earth sciences -- Periodicals; 551.1
• DOI: 10.1002/2014JB011050
• Languages: English
• ISSNs: 2169-9313

Abstract

<abstract abstract-type="main"> <title>Abstract</title> <p>Shallow explosive volcanic processes, such as kimberlite volcanism and phreatomagmatic and phreatic activity, produce volcanic vents exhibiting a wide variety of morphologies, including vertical pipes and V‐shaped vents. In this study we report on experimental and numerical models designed to capture a range of vent morphologies in an eruptive system. Using dimensional analysis, we identified key governing dimensionless parameters, in particular the gravitational stress‐to‐fluid pressure ratio (Π<sub>2</sub> <italic>= P/ρgh</italic>) and the fluid pressure‐to‐host rock strength ratio (Π<sub>3</sub> = P/<italic>C</italic>). We used combined experimental and numerical models to test the effects of these parameters. The experiments were used to test the effect of Π<sub>2</sub> on vent morphology and dynamics. A phase diagram demonstrates a separation between two distinct morphologies, with vertical structures occurring at high values of Π<sub>2</sub> and diagonal ones at low values of Π<sub>2</sub>. The numerical simulations were used to test the effect of Π<sub>3</sub> on vent morphology and dynamics. In the numerical models we see three distinct morphologies: vertical pipes are produced at high values of Π<sub>3</sub>, diagonal pipes at low values of Π<sub>3</sub>, and horizontal sills at intermediate values of Π<sub>3</sub>. Our results show that vertical pipes form by plasticity‐dominated yielding in high‐energy systems (high Π<sub>2</sub> and Π<sub>3</sub>), whereas diagonal and horizontal vents dominantly form by fracturing in lower energy systems (low Π<sub>2</sub> and Π<sub>3</sub>). Although our models are two‐dimensional, they suggest that circular pipes result from plastic yielding of the host rock in a high‐energy regime, whereas V‐shaped volcanic vents result from fracturing of the host rock in lower energy systems.</p> </abstract>