Volcanoes • Earthquakes • Volcano Monitoring • New Research
More earthquakes around a reawakening volcano might sound like a simple sign that pressure and energy are building underground. But new research reveals something much stranger: as fractures grow and progressively weaken the crust, the amount of elastic energy stored in the surrounding rock can actually fall — even as the volcanic system becomes increasingly capable of rupture.
When a long-dormant volcano begins shaking again, the obvious interpretation seems simple.
More earthquakes = more stress = more energy building underground.
And eventually:
boom.
But volcanoes rarely cooperate with simple explanations.
New research published in Nature Communications suggests that during a critical stage of volcanic unrest, almost the opposite can happen.
Volcano-tectonic earthquakes can accelerate while the amount of elastic energy stored in the surrounding crust is actually decreasing.
That apparent contradiction isn’t necessarily reassuring.
It can mean that fractures are growing.
The crust is weakening.
And the pressurized volcanic system underneath may be becoming increasingly capable of rupturing the rock above it.
More earthquakes can accompany less stored elastic energy — because the crust is starting to break.
Researchers Eric L. Newland and Christopher R. J. Kilburn of University College London have now developed an energy-budget method designed to identify when that transition begins.
The approach could provide another piece of information for scientists trying to understand one of volcanology’s hardest problems:
When does volcanic unrest stop being merely unrest and begin moving toward crustal failure?
Why Volcanoes Start Shaking After Long Periods of Silence
A volcano can remain quiet for decades, centuries or considerably longer without becoming geologically dead.
Magma and other pressurized fluids may still exist beneath the volcanic system.
When pressure begins increasing several kilometers underground, the overlying crust starts deforming.
That deformation can reactivate existing faults and open new fractures.
The result is often increasing numbers of volcano-tectonic earthquakes.
These earthquakes are produced when brittle rock breaks or slips under changing stress conditions around the volcanic system.
They are therefore one of the signals scientists watch closely during volcano monitoring and eruption forecasting.
But earthquake numbers alone don’t tell scientists exactly what the crust is doing.
A swarm can indicate that rock is being stressed.
It can indicate that faults are slipping.
It can indicate magma or fluids are moving.
And critically, it can indicate that fractures are beginning to grow.
The Counterintuitive Part: More Earthquakes, Less Stored Energy
Imagine slowly bending a rigid piece of material.
Before it breaks, the material stores elastic energy.
Rock behaves differently in detail, but the basic idea is useful.
As a volcanic pressure source deforms the crust, part of the energy supplied to the surrounding rock can be stored elastically.
Initially, the crust can accommodate that deformation without undergoing large-scale fracture growth.
But eventually something changes.
Fractures begin extending.
Earthquakes release energy.
Rock is damaged.
And some of the energy entering the system is increasingly consumed by the physical process of breaking the crust rather than simply being stored within it.
The researchers found that this transition toward fracture growth is associated with a net decrease in stored elastic energy.
So a volcano can display increasingly energetic-looking seismic unrest while its crust is actually becoming less capable of storing elastic energy.
That’s the paradox.
Think of It as a Crust That Is Losing Strength
The distinction between stored energy and rock strength is essential.
A decline in stored elastic energy does not mean the volcanic system has simply become safer.
It can mean energy is being consumed by irreversible damage.
New fractures open.
Existing fractures extend.
Faults slip.
The rock mass becomes progressively weakened.
Eventually, fractures may become large enough and sufficiently connected to allow rupture through the crust.
For a reawakening volcano, that transition is potentially critical.
The fundamentals of how pressure, magma, gases and fractured crust interact are explored further in our guide to volcano science.
A New Way to Follow the Volcano’s Energy Budget
Newland and Kilburn approached the problem as an energy budget.
At its simplest, energy is being supplied to the crust by the pressurizing volcanic source.
At the same time, energy is being lost through seismic activity and fracture growth.
By comparing those competing processes, the researchers developed a method for tracking how much elastic energy remains stored in the crust during volcanic unrest.
The important moment is when the behavior changes from predominantly storing deformation energy to increasingly consuming that energy through fracture growth.
That transition may provide scientists with a way of identifying when the crust has entered a more advanced stage of weakening.
The basic sequence looks like this:
Pressurization ↑
→ crustal deformation
→ volcano-tectonic earthquakes ↑
→ fractures begin growing
→ stored elastic energy ↓
→ crust weakens
→ potential for crustal rupture ↑
Why Earthquake Numbers Alone Can Be Misleading
This is where the research becomes particularly interesting for earthquake science.
Earthquakes are evidence that rock is responding to stress, but seismicity doesn’t provide a simple gauge showing how much usable elastic energy remains stored in the crust.
An accelerating earthquake sequence might intuitively suggest that the crust is storing progressively more energy.
But once significant fracture growth begins, increasing seismicity can accompany a decline in stored elastic energy.
That’s because the rock is no longer behaving primarily as an elastic body.
It is being damaged.
In other words:
The increasing earthquakes may partly be the sound of the crust losing its ability to resist rupture.
Campi Flegrei Put the Method to the Test
The researchers tested their approach against unrest at two large volcanic calderas:
- Campi Flegrei in southern Italy;
- and Sierra Negra in the Galápagos Islands.
Campi Flegrei is particularly interesting because it has experienced repeated episodes of ground uplift and earthquake activity associated with its restless subsurface system.
Rather than being a classic steep volcanic cone, Campi Flegrei is a large volcanic caldera occupying an intensely populated part of the Naples region.
Calderas form when large volcanic systems undergo major structural collapse, often leaving enormous depressions rather than recognizable cone-shaped volcanoes.
Because some caldera systems are capable of exceptionally large eruptions, they are also frequently discussed alongside supervolcanoes.
But the new study should not be interpreted as saying that Campi Flegrei is about to erupt.
Campi Flegrei is being used here as a real-world volcanic system against which the researchers can test whether their energy-budget approach captures changes during observed unrest.
Sierra Negra Provides a Second Natural Laboratory
The second test case was Sierra Negra, a large shield volcano on Isabela Island in the Galápagos.
Sierra Negra provides a very different volcanic setting from Campi Flegrei.
Yet both systems allow scientists to compare changes in deformation and seismic activity against the proposed evolution of stored crustal energy.
Testing the method against two different caldera systems is important because volcanoes vary enormously in their magma composition, crustal structure, geometry, tectonic environment and eruption behavior.
Those differences are why volcanoes must always be understood within their broader volcanic and tectonic regions.
Does This Mean Scientists Can Predict Volcanic Eruptions?
No.
And that’s an important distinction.
The new method does not provide a countdown clock to the next eruption.
It does not mean scientists can look at an earthquake swarm and announce that a volcano will erupt in three days, three weeks or three months.
What the researchers propose is more specific.
Their method is designed to help identify the onset of significant fracture growth.
Recognizing that transition may indicate that the crust has entered a state with an increased potential for rupture.
That’s valuable information.
But rupture potential is not the same thing as an eruption prediction.
Volcano Forecasting Is a Multi-Signal Problem
Modern volcano observatories don’t rely on a single warning sign.
Scientists combine multiple streams of information, including:
- earthquake frequency, depth and magnitude;
- ground deformation measured by GPS and satellite radar;
- volcanic gas emissions;
- changes in fumaroles and hydrothermal systems;
- thermal anomalies;
- gravity changes;
- magma and fluid movement;
- and the volcano’s previous eruptive behavior.
Each signal describes a different part of what is happening underground.
Seismicity tells scientists where brittle failure is occurring.
Deformation reveals how the crust is changing shape.
Gas chemistry can reveal changes in magma and hydrothermal systems.
Satellite observations can detect deformation across entire volcanic regions.
The proposed energy-budget method could potentially add another diagnostic:
Is the crust still primarily storing deformation energy — or has significant fracture growth begun?
See Volcano Monitoring & Forecasting Explained
for how scientists combine these different signals when evaluating volcanic unrest.
Why Long-Dormant Volcanoes Are Particularly Difficult
The study specifically focuses on volcanoes reawakening after long periods of repose.
That’s a particularly difficult forecasting problem.
Frequently active volcanoes can provide scientists with repeated examples of what their normal unrest looks like before, during and after eruptions.
A volcano that has been quiet for generations may offer much less modern instrumental evidence.
Scientists may have no directly observed example of how that particular system behaves before an eruption.
When seismicity suddenly increases beneath such a volcano, the key question becomes:
Is this another episode of unrest that will eventually fade — or is the crust actually progressing toward failure?
Most episodes of volcanic unrest do not automatically culminate in eruption.
Being able to identify physical transitions within the crust could therefore help distinguish different stages of that unrest.
Why Fractures Matter So Much
Magma cannot erupt simply because magma exists underground.
It needs a pathway.
The surrounding crust acts as a mechanical barrier.
Pressure from magma and volcanic fluids deforms that barrier.
Faults and fractures provide weaknesses.
As those fractures propagate and connect, they can potentially create pathways through which magma or fluids move upward.
This means understanding fracture growth isn’t merely an earthquake problem.
It’s fundamental to understanding how a pressurized volcanic system can eventually breach the crust.
A Volcano Doesn’t Have to Store More Energy to Become More Dangerous
And that’s the genuinely counterintuitive lesson from the research.
We tend to imagine geological disasters as systems that become progressively more dangerous because they continuously accumulate more and more energy.
Sometimes that’s useful.
But failure can also become more likely because the material containing that energy is becoming weaker.
Imagine increasing pressure inside a perfectly strong container.
One route toward failure is to keep increasing the pressure.
But there’s another route.
Weaken the container.
A damaged container can fail under conditions that a stronger one could withstand.
The volcanic crust can behave in a similarly counterintuitive way.
The critical change may not simply be how much energy is accumulating.
It may be how efficiently the surrounding rock can continue storing that energy without breaking.
What Scientists May Be Listening for Is the Crust Beginning to Fail
Volcano monitoring has always involved trying to interpret signals generated kilometers beneath our feet.
Earthquakes.
Swelling ground.
Escaping gases.
Changing temperatures.
Tiny movements detectable only from satellites or extremely sensitive instruments.
The new research adds another way of interpreting those signals.
An accelerating earthquake sequence doesn’t necessarily mean the crust is simply becoming more heavily loaded with stored elastic energy.
It may indicate that the crust has crossed into a different mechanical state.
Fractures are growing.
Energy is being dissipated through damage.
The rock is weakening.
And the barrier holding the volcanic system below may be becoming progressively easier to rupture.
Sometimes the warning isn’t that more energy is being stored underground. It’s that the rock containing it is becoming less capable of holding it.
What This Research Does — and Does Not — Tell Us
The study provides a new framework for interpreting the mechanical evolution of volcanic unrest.
It does not mean every accelerating earthquake swarm signals an imminent eruption.
It does not mean falling stored elastic energy automatically means magma will reach the surface.
And it does not replace established volcano-monitoring techniques.
Instead, the researchers propose a practical way to identify a potentially important transition:
the point at which growing fractures begin progressively weakening the crust.
If the method proves useful across additional volcanic systems, it could become another tool for understanding when long-dormant volcanoes move from pressurization toward more advanced stages of crustal failure.
For the bigger picture, explore our Volcanoes hub, which connects volcano science, eruption mechanisms, hazards, monitoring, major volcanic regions and some of Earth’s most extraordinary volcanic systems.
Frequently Asked Questions About Volcano Crustal Weakening
Can a volcano become more dangerous while stored elastic energy is falling?
Yes. The new research suggests that once significant fracture growth begins, some of the energy supplied to the crust is increasingly consumed by breaking and damaging rock rather than being stored elastically. That means stored elastic energy can decline while the crust becomes progressively weaker and more capable of rupture.
Why do earthquakes increase around a reawakening volcano?
Increasing pressure from magma or other volcanic fluids can deform the surrounding crust, reactivate existing faults and create new fractures. These brittle failures generate volcano-tectonic earthquakes.
Does more volcanic earthquake activity always mean an eruption is imminent?
No. Many episodes of volcanic unrest do not end in eruption. Increasing seismicity can indicate deformation, fault slip, fluid movement or fracture growth, but scientists must combine earthquake data with ground deformation, gas emissions, thermal changes and other monitoring signals.
What is stored elastic energy in the crust?
Stored elastic energy is mechanical energy accumulated as rock deforms under stress without permanently breaking. Once fractures begin growing significantly, more energy can be dissipated through irreversible rock damage and seismic activity.
What is the new volcano warning signal proposed by the study?
The researchers propose tracking the volcano’s crustal energy budget to identify when significant fracture growth begins. That transition may indicate that the crust is entering a more weakened state with increased potential for rupture.
Does this research predict when Campi Flegrei will erupt?
No. Campi Flegrei was used as one of the real-world volcanic systems against which the researchers tested their method. The study does not provide an eruption date or say that an eruption is imminent.
What is the difference between crustal rupture and a volcanic eruption?
Crustal rupture refers to rock breaking and fractures propagating through the crust. An eruption requires additional conditions, including magma or volcanic fluids successfully exploiting pathways toward the surface. Increased rupture potential therefore does not automatically mean an eruption will occur.
Study
Newland, E. L. & Kilburn, C. R. J. — “Crustal weakening before rupture at volcanoes after long repose”
Nature Communications
Published: August 24, 2026
DOI: 10.1038/s41467-026-77001-5
Read the original open-access study in Nature Communications
