3.10 Monitoring Volcanoes and Predicting Eruptions

GEOL1340

Precursor Signals

Physical and chemical changes (such as earthquake swarms, gas release, and ground swelling) that indicate magma is moving upward toward the surface.

Harmonic Tremor

Continuous, low-frequency seismic vibrations caused by the steady flow of magma and volcanic gases underground.

Cause of Volcanic Earthquakes

Rising magma forcing its way through the crust, causing brittle deformation, fracturing surrounding rock, and increasing localized pressure.

Volcanic Inflation

The swelling and tilting of the ground above a volcano caused by magma or gas filling an underground magma chamber.

Tiltmeter

A sensitive instrument that measures micro-changes in the slope or angle of the ground surface at a specific location.

GPS Tracking in Volcanology

Satellite technology used to track precise 3D ground movements (east-west, north-south, and up-down) to detect volcanic inflation or deflation.

InSAR / LiDAR

Satellite and remote sensing technologies used to detect broad, millimeter-scale surface elevation changes across an entire volcanic edifice.

Key Volcanic Gases Monitored

Water Vapor (H2O), Carbon Dioxide (CO2), Sulfur Dioxide (SO2), and Hydrogen Sulfide (H2S).

Significance of Increasing SO2 Emissions

Indicates that magma is ascending close to the surface, where lower pressure allows dissolved sulfur gases to rapidly escape.

Phreatic Eruption (Blowing Off Steam)

An explosive steam eruption triggered when rising magma heats underground groundwater to the boiling point.

Phreatic Bulge (Big Bump)

A prominent swell on the flank of a volcano created when magma moves extremely close to the surface (e.g., Mount St. Helens in 1980).

Volcanic Seismometer Network

The simplest and most cost-effective continuous monitoring tool used to detect early subsurface magma movement.

Chris Newhall's 6 Signs of Imminent Eruption

Gas leaks, bit of a bulge, getting shaky (earthquakes), dropping fast (stalled seismicity), big bump, and blowing off steam (phreatic eruptions).

Cause of a Sudden Drop in Volcanic Seismicity

Can indicate that ascending magma has temporarily stalled, building pressure until overlying rock catastrophically gives way.

Acid Rain Chemical Equation

CO2 + H2O -> H2CO3 (Carbonic Acid) or SO2 + H2O -> Sulfuric Acid compounds.

Tsunami Triggers in Volcanic Regions

Submarine volcanic explosions or large sector/flank collapses into surrounding marine waters displacing massive volumes of water.

Mechanism of Global Climate Cooling by Volcanoes

Injection of sulfur dioxide (SO2) aerosols into the stratosphere reflects incoming solar radiation back into space.

Primary Volcanic Hazards in Western Canada

Garibaldi Volcanic Belt (Mt. Garibaldi, Mt. Meager) and transboundary threats from Mt. Baker (ashfall, lahars, debris avalanches).

Volcanic Hazard Context in Central Canada (Manitoba)

No active volcanic hazards today; Precambrian volcanic rocks in the Canadian Shield are over two billion years old.

Short-term vs. Long-term Eruption Prediction Ability

Volcanologists can forecast eruptions over weeks to months based on precursor signals, but cannot pinpoint exact days or hours in advance.