Explosive-effusive volcanic eruption transitions caused by sintering

Area of Science:

• Volcanology
• Earth Science
• Geology

Background:

• Silicic volcanic activity is traditionally categorized as either explosive or effusive.
• Recent observations indicate simultaneous explosive and effusive eruptive behaviors.

Purpose of the Study:

• To propose a new model for rhyolitic volcanic eruptions.
• To explain how both explosive and effusive eruptions can originate from the same magma system.
• To reconcile paradoxical observations in silicic volcanism.

Main Methods:

• Analysis of volatile-depleted rhyolitic lavas.
• Examination of textural evidence in effusive volcanic products.
• Numerical modeling of ash particle degassing, sticking, and sintering.
• Comparison of inferred ascent rates for explosive and effusive eruptions.

Main Results:

• Rhyolitic lavas are characterized by volatile depletion.
• Textural evidence suggests effusive products originate from pyroclastic material.
• Numerical models demonstrate that small ash particles can sinter into low-porosity structures during ascent.
• Ascent rates for explosive and effusive eruptions show overlap.

Conclusions:

• The proposed model suggests that rhyolitic magma fragments during ascent, with effusive eruptions resulting from conduit blockage and sintering of deeper fragmented material.
• This framework reconciles simultaneous explosive and effusive activity.
• Offers a new perspective for evaluating volcanic eruption models.