Magma rheology, degassing and eruption style
Magma ascent can lower confining pressure enough for dissolved volatiles to exsolve and expand.
Key knowledge
Magma ascent can lower confining pressure enough for dissolved volatiles to exsolve and expand. Whether gas escapes or remains coupled to magma depends on viscosity, permeability, ascent and decompression history. Efficient gas escape can favour an effusive lava eruption; trapped expanding gas can favour explosive behaviour. Composition affects melt viscosity, but a composition label alone does not uniquely predict an eruption style.
Conditions and scope
- Use the actual melt/crystal/bubble state, temperature, volatile species and pressure history. Silica-network polymerization is one compositional influence; crystals and bubbles can change bulk rheology.
- Not every basaltic eruption is effusive or every felsic eruption explosive. Water–magma interaction and conduit conditions add mechanisms; the qualitative reference is not an operational volcano forecast or a universal fragmentation threshold.
Sources · 2
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Steven Earle — Physical Geology2e (2019)2 sources
Evidence and review
Read actual§4.2 polymerization/volatile-pressure/escape/effusive–explosive bodies and§4.1 melting settings. Retained conditional mechanism, excluding fixed volatile/temperature percentages, universal gas ranking, blanket basalt/nonexplosive predictions, claims that subducted crust never melts and a single universal plume origin. Temperature/crystal/bubble and water-interaction caveats restrict inference rather than introducing an uninspected quantitative closure.
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Entry details
Permanent link to this entry ↗- Record identity
- uni-earth-volcanic-eruption-controls
- Revision
- core.1
- Structured reference record
- University core expansion