Why do volcanoes erupt in different ways?: sources & model
Watch real lava feed a channel. Take apart a gas-volume calculation, compare Mount St. Helens through time, inspect volcanic rock under a microscope and explore an actual surveyed crater.
The source and model records are available for inspection. No external scientific reviewer has signed off yet.
gas-space-reference-1 · content 1 · setup format 1
What supports the explanation?
Sixteen source pressure states, volatile mass fractions and gas/melt volume ratios.
USGS OFR 95-756, upper Table 2, printed page 38 / PDF page 43. Historical equilibrium calculation. The displayed derivative CSV is transcribed from the original table.
Fissure 20 fountaining and flowing lava in the same recorded activity.
USGS-created footage, public domain in the US. Self-hosted full-duration silent 960 × 540 derivative and credited stills at source times 10 and 35 seconds.
A low-viscosity fountain can produce separate fragments through distinct processes.
Authors report dominant fluidal fragmentation and interpret a smaller vesicular population in terms of rapid gas separation and cooling. Our video is not a particle-temperature measurement.
Measured rock microstructure, thermal-history comparisons and permeability detection limit.
Bulletin of Volcanology 78:30. Figures 1 and 6, CC BY 4.0, preserved in full with 500 µm scale bars. Resized/WebP-encoded images do not add detail. Bulk porosity is distinct from image porosity.
October 5, 2022 summit elevation data, registration context and stated accuracy limits.
Original USGS FOIA release DOI-USGS-2023-000279, preserved in Ben Welsh’s pinned public-records distribution. Full source hash, 257 × 257 sample mapping, missing values and derivative hashes accompany the lesson.
The gas workbench uses a historical calculated basalt example. It is not a measurement of the pictured eruptions, a live monitoring feed or a hazard forecast.
Pressure choices are discrete source rows. No interpolated viscosity, ascent speed, depth, eruption countdown or universal fragmentation threshold is calculated.
The gas-retention intervention holds pressure and normalized melt volume fixed. It omits transport rates, pressure adjustment after loss and real open-system ascent. Choosing another pressure restores the complete source row.
All mass percentages displayed beside the retention experiment describe the unmodified source state. We do not claim to recalculate remaining gas mass after removal.
The rock figures are full original two-dimensional sections of specific crystalline dome samples. Their treatments, porosity methods and permeability observations stay separate.
The Kīlauea Fissure 20 footage is from May 2018; the summit survey is from October 2022. They are different locations and records. Underground structures are not inferred from the surface mesh.
Source footage is silent and preserves framing and dates. The dome footage is a time-lapse. No artificial explosions, live-event claims or inferred personal risk scores are added.
The paper activity represents routes and volume bookkeeping. It does not reproduce real magma chemistry, pore geometry or an eruption. Independent subject and learner review remains pending.
Read the original calculation precisely: The sixteen discrete states come from the upper Table 2 in Mastin’s 1995 USGS Open-File Report 95-756, printed page 38. Its reservoir-equilibrated Kīlauean basalt example begins with 0.27 wt% water, 0.0195 wt% carbon dioxide and 0.07 wt% sulfur. The original report uses steady homogeneous flow and equilibrium volatile partitioning. We read its reference table; we do not reimplement or validate its entire conduit solver.
Derive the fraction from its definition: Let R be gas volume divided by melt volume. Normalizing melt volume to 1 gives gas fraction R/(1+R). If the retained share is f at fixed pressure and melt volume, the remaining fraction is fR/(1+fR). At 0.5 MPa, R is 6.3952. Retaining half gives 3.1976/(1+3.1976), approximately 76.2%, rather than half of 86.5%.
Changing pressure is not just expanding a fixed gas amount: The selected equilibrium source table includes gas separating from the melt as conditions change. Between 0.5 and 0.2 MPa, the source gas/melt volume ratio increases by about 3.263 times. A separate fixed-amount isothermal ideal-gas comparison would expand by 2.5 times. Those are different models, not contradictory measurements.
Porosity and permeability answer different questions: Gaunt and colleagues studied crystalline dome rock from Mount St. Helens. The intact section’s image porosity is 6.7%, while the separately reported connected bulk porosity is 6.0%. The pictured plane is perpendicular to the experiment’s fluid-flow direction. Cyclically heated and once-heated images show 2.1% and 5.5% porosity; those discrete samples do not establish a universal continuous temperature curve.
An upper bound is not zero: At 900 °C, flow could not be resolved over the study’s observation period. The authors describe an approximate permeability upper bound of 10⁻¹⁹ m². An instrument’s lack of detected flow is different from proving that all flow is impossible.
A material can remember its path: Gonnermann and colleagues’ experiments on Glass Mountain pumice showed that expansion and compaction can produce different relationships between porosity and permeability. This supports keeping history and sample context attached to a claim. It does not supply a universal pore percentage that predicts every magma’s fragmentation.
A surveyed mesh has uncertainty: Our summit surface samples an actual USGS HVO October 5, 2022 elevation raster. The source reports no formal accuracy tests; stated horizontal and vertical targets are not measured errors. We preserve absent samples and source pixel-center coordinates. A 1-meter source pixel does not establish 1-meter accuracy or a certified sea-level datum.
What has been checked
Analytical reference cases, conservation or transition invariants, finite drawing commands, bounded setup parsing, discovery and route integrity are checked automatically. These checks do not establish anatomical fidelity, learner outcomes or browser/device compatibility. Independent subject review, learner trials, comprehensive accessibility review and browser video encoding checks remain pending.
Each source supports the associated claim. Sources do not certify this implementation or its visuals.
About the cover illustration
USGS HVO May 21, 2018 Fissure 20 overflight, original frame at 10 seconds. Full source framing retained. Public domain in the US; historical footage, not a live volcano.