SCIENCE · INVESTIGATE AND EXPLAIN

Explain melting without a global molten layer

Distinguish partial melting, magma movement, intrusion and eruption in their geological settings.

Learning outcome: Explain decompression and volatile effects without treating the mantle as a liquid ocean.

Starting recap

Kilauea is a hot-spot example; convergent motion alone does not establish subduction melting.

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Try

The January-February intrusion moved magma without reaching the surface.

Open the experiment

Predict

Must magma migration always lead to a surface eruption?

Your prediction and reason

Experiment

Order process cards, annotate ridge/subduction/hot-spot cross-sections and inspect the January intrusion outcome.

Interpret dated volcano monitoring evidence

Historical USGS monitoring summaries · separate worked geometry · Three historical 2024 USGS HVO reports, not current conditions. Published summaries retain inequalities, approximation, intervals, differing header/identifier times and unavailable uncertainty. Tilt, displacement, seismic counts and surface observations answer different questions. Revealing facts is guided practice, not a forecast, source inversion or independent hazard expertise.

Historical evidence packet: June 3 preliminary monitoring update Evidence view: Deformation evidence

Reset keeps your prediction, captures and practice history.

From solid mantle to magma movement

Original cross-sections below are qualitative and not to scale. Trace the arrows and explain which change permits partial melting. The mantle is predominantly solid; magma is not a global ocean beneath floating plates.

Kīlauea illustrates a hot-spot setting. Its historical monitoring records do not demonstrate subduction. Identical convergent arrows could describe an oceanic subduction setting or continental collision: velocity signs alone cannot identify the material or melting mechanism. Transform motion alone is not a universal cause of melting.

Partial melting, ascent, storage, crystallization, intrusion and eruption are different processes. A dike is a sheet-like intrusion; it can stop below the surface. Gas release and escape, viscosity, temperature, composition and confinement influence eruption behavior. No single composition label guarantees an eruption style.

Paper action: draw a path that ends in an intrusion and another that reaches the surface. Add the evidence that would distinguish them. Background: National Park Service explanation of magma and eruption types.

Historical monitoring evidence — 2024

June 3 preliminary monitoring update · June 2–3, 2024; preliminary June 3 update. These are selected published summaries, not a raw instrument time series or current conditions. Switching views reveals more of a fixed record. Source links remain available, so this is guided evidence practice, not a hidden assessment.

Read the original USGS HVO notice. Scientific report header: 2024-06-03 09:38 HST (2024-06-03T19:38:00Z). The notice identifier contains 2024-06-03T19:34:15+00:00; that identifier time differs from the displayed scientific header. Do not substitute one for the other.

What the instruments constrain
Method	Meaning and limits
Tiltmeter	Change in local ground slope, in microradians; not height.
GNSS	Position/displacement in a stated frame; an unspecified vector magnitude is not vertical uplift.
Satellite deformation analysis	Spatial motion inferred with acquisition geometry and assumptions; selected uplift is an agency interpretation, not raw line-of-sight data.
Seismic network	Ground shaking used to detect events; published counts depend on selection and detectability.

Revealed quantities retain their original units, qualifiers and observation windows
Instrument and place	Reported quantity	Direction	Observation interval	Evidence kind
Tiltmeter Uēkahuna	approximately 14 microradian	deflation	Past day relative to June 3 report; endpoints not stated	Published measurement summary Numerical uncertainty: unavailable
Tiltmeter Sand Hill	approximately 50 microradian	inflation	June 2 08:00–20:00 HST Start: 2024-06-02T18:00:00Z End: 2024-06-03T06:00:00Z	Published measurement summary Numerical uncertainty: unavailable
Tiltmeter Sand Hill	approximately 35 microradian	deflation	June 2 20:00 HST to this morning; exact end unspecified Start: 2024-06-03T06:00:00Z	Published measurement summary Numerical uncertainty: unavailable

Earthquake summaries are not shown in this view. This is not a report of zero earthquakes.

Surface observations: Surface observations are not shown in this teaching view; this does not mean no eruption.

Dated gas context: Not shown in this teaching view.

Inspect unit conversions and mean-rate arithmetic

Conversions preserve the measured quantity; they do not change tilt into uplift or event count into energy. A mean over a stated interval is not an instantaneous rate. Strict bounds retain their exact arithmetic expression; the rounded boundary is only an aid to reading.

Conversions of currently revealed source quantities
Source row	Converted value
June 3: Uēkahuna tilt	approximately 0.0008021 degrees
June 2: Sand Hill inflation	approximately 0.002865 degrees
June 3: Sand Hill deflation	approximately 0.002005 degrees

Mean rates only when the notice supplies a duration
Source row	Hours	Mean-rate statement
June 3: Uēkahuna tilt	24	approximately 0.5833 microradians/hour
June 2: Sand Hill inflation	12	approximately 4.167 microradians/hour
June 3: Sand Hill deflation	Unspecified	Interval not specified; mean rate unavailable.

For example, 50 microradians over 12 hours gives an approximate mean of 50/12 = 4.17 microradians/hour. A later 35-microradian change with no exact endpoint cannot supply an hourly rate. Do not subtract approximate counts from strict lower bounds to invent exact counts in another interval.

Questions the evidence can and cannot answer

What ground changes does each stated instrument summary report?

Still unresolved:

What unique subsurface geometry or magma volume would explain these limited summaries?
What additional observations would discriminate alternative explanations?
What surface observations and dated gas context are not yet shown?

Try a common-frame displacement comparison

Original worked geometry, separate from the USGS observations. Two stations start 1,000 m apart along an east–west baseline. Both use the same reference frame. Predict the distance change before opening the arithmetic. Positive displacement points east.

Reveal baseline arithmetic

Exact horizontal teaching cases, not measured deformation
Case	A east mm	B east mm	B − A mm	Length change mm
Shared translation	20	20	0	0.000
Extension	-10	10	20	20.000
Contraction	10	-10	-20	-20.000

Common translation moves both stations while preserving their separation. Two stations constrain one baseline, not the full deformation field or magma volume. Motion perpendicular to the baseline changes its orientation and produces only a second-order length change for a small displacement; a rotation can preserve length without being a translation.

Transfer: A moves 5 mm east and B moves 25 mm east. Calculate relative displacement and explain why shifting the shared reference origin does not change it.

Connect tilt to an explicitly assumed geometry

Original paper example: a rigid straight beam spans a horizontal 10 m and tilts through 50 microradians. One microradian is one millionth of a radian. The angle is 0.00286479 degrees; height difference = 10 × tan(50 × 10⁻⁶) m, approximately 0.500 mm. For this small angle, replacing tan(angle) with angle gives nearly the same result.

This is not observed uplift at Sand Hill. Local ground slope does not specify a rigid 10 m beam, spatial deformation field or magma volume. Change the paper baseline to 20 m and predict the height difference under the same deliberately imposed geometry.

Inspect historical provenance and missing information

Version: volcano-evidence-v1. Selected factual summaries are attributed to USGS HVO; no external image is copied. Retrieved 2026-10-26T17:00:32.219464+00:00. Missing numerical uncertainty means unavailable, not zero error. The records do not reconstruct raw GNSS vectors, satellite viewing geometry or a complete earthquake catalog.

Selected-data SHA-256: 4c40c2cd1641ceaafea4ff7fa9efe9a244c17def57661a37017acd8b6b571b72

Retrieved source HTML SHA-256: d4dec04e7feb65b3032600e715c903a80d0ca26e567a07549fc30a4badb060a6; 21977 bytes.

Source identifier: DOI-USGS-HVO-2024-06-03T19:34:15+00:00. Historical alert levels are not displayed as present-day guidance.

Deformation summaries are available. Surface outcome is not shown; no eruption probability or date is inferred.

volcano-evidence-v1; 2024-06-03 09:38 HST. 3 deformation summaries, 0 earthquake summaries and 0 dated gas summaries shown. Qualifiers and observation intervals remain attached; hidden evidence is not absent evidence.

Observation to attach to a capture

Captures preserve the historical packet and evidence view. Replaying reveals fixed published summaries and their limits; it does not create new measurements, an independent prediction or an eruption forecast.

Understand

Separate making magma from erupting it

Arrange five paper cards: mostly solid mantle, partial melting, magma migration, intrusion and eruption. Put a question mark between intrusion and eruption. Does moving magma necessarily reach the surface? Keep your prediction for comparison with the January–February historical packet later in the investigation.

Magma is molten material below the surface, commonly accompanied by crystals and dissolved gases. Lava is magma that has erupted. Partial melting means that some material melts while other material remains solid. It does not require a continuous global ocean of liquid beneath tectonic plates.

The USGS explanation of mantle and magma provides the important starting distinction: mantle rock is predominantly solid, even though it can deform over geological time. The diagram here is an original qualitative cross-section, not a measured temperature or melt-fraction map.

Compare mechanisms in their geological settings

At a divergent setting, hot mantle can rise into lower pressure and partially melt without additional heating. This is decompression melting. On your rising-rock card, draw an upward arrow and label the pressure change. Do not draw a flame underneath merely because melting occurs.

At a subduction setting, water and other volatiles released from descending material can lower the melting threshold of overlying mantle material. Draw the fluid-transfer arrow separately from the slab-motion arrow. This is not a claim that friction melts an entire descending plate. Continental collision can also produce convergent surface motion, so convergence alone does not establish the slab geometry or this mechanism.

Hot-spot settings can generate magma through mantle upwelling and thermal conditions away from a plate boundary. Kīlauea is a hot-spot example, not a subduction-zone volcano. Transform-style motion alone is not a universal magma-production mechanism. The NPS account of magma and eruption types provides additional mechanism context.

Compare the three original cross-sections. For each, name the changing condition and the geological evidence you would need to justify that setting. No numerical melting temperature is supplied, so do not invent a threshold or calculate a melt fraction from the drawing.

Follow movement after melting

A dike is a sheet-like intrusion: magma enters a fracture or opening within rock. Buoyancy and pressure gradients can promote movement, but the route is not an unobstructed pipe. Magma may accumulate, move sideways, cool or crystallize without erupting. Making melt, storing it and releasing it at the surface are distinct processes.

Magma and fluid movement can deform surrounding rock and trigger fractures. Some movement occurs without located earthquakes. As pressure decreases, dissolved gas can leave solution; whether gas escapes or remains confined affects behavior. Viscosity, temperature, composition and gas conditions all matter. Avoid replacing these interactions with a rule that one ingredient guarantees an explosive eruption.

Test the cards against a historical outcome

Select the January 27–February 3 intrusion packet and progress through the cumulative evidence views. Preserve a prediction from deformation alone, then add earthquakes and the reported surface outcome. The February 9 HVO statement interprets the episode as an intrusion that did not reach the surface.

That outcome tests the claim that any magma movement must erupt. The monitoring summaries do not calculate the earlier melting process that generated this magma. Your paper mechanism cards explain possible geological processes; the historical notice concerns a particular movement episode. Do not turn one Kīlauea sequence into a universal timeline for every volcano.

Transfer: change the tectonic context

An unfamiliar divergent setting includes hot mantle rising as plates separate. A report copies the Kīlauea dates and says frictional melting must cause an eruption after the same delay. Replace both unsupported claims with a mechanism and a bounded conclusion.

Check the magma-pathways transfer

Rising hot mantle can undergo decompression melting as pressure decreases. That does not establish a surface eruption or its date. Ascent, storage and intrusion require separate evidence, and dates from one historical Kīlauea episode do not determine another setting's behavior.

Apply

Public practice checks a specific claim. It does not establish independent mastery.

Separate melt production from later movement of stored magma and identify missing setting evidence.

Your explanation and limitations

Continue

Completion requires a saved prediction, at least one capture and a reflection. Presence checks do not grade your reasoning.

Skipping retains experiments and awards no mastery.

Previous: Build an evidence-limited cosmic argument Next: Read what each deformation instrument measures

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