Volcano eruption: Ground Deformation & Geochemistry

• Recognizing the signs of an impending volcanic eruption and interpreting different volcano hazards are important skills.

Ground Deformation

• Ground deformation is surface changes on a volcano.
• Subsidence (sinking), tilting, or bulge formation are examples of ground deformation.
• Movement of magma below the surface causes ground deformation.
• An Electronic Distance Meter (EDM) is used to measure millimeter changes on the ground if the slope for the volcano swells.
• Data of repeated measurements from a permanent Global Positioning System (GPS) installed around the volcano is also used to measure ground deformation.
• Remote sensing images help compare before and after features.

Geochemistry

• Equipment, Instruments and Tools are used in Geochemistry.
• Direct measurements of temperature and water chemistry of ground water, spring water or lakes uses a thermometer/thermocouple, pH meter.
• Gas being emitted by volcanoes can be measured directly by gas monitoring equipment.
• Gas and water samples from vents and fumaroles are collected to be analyzed in a lab using X-Ray Fluorescence (XRF).
• Remote gas monitoring equipment includes: COSPEC- correlation spectrometer for FlySPEC/ ScanDOAS for SO2; and CO2 flux meter for CO2.
• Changes in temperature or increased acidity in water can indicate unrest.
• Some gas, for example SO2 from base levels of 100 tons/day jumping to 4,000 tons/day can indicate unrest.

Seismic Activity

• Seismometers are equipment used to detect volcanic earthquakes.

Sensory Observations

• Visual signs include intensified steaming activity, and steam slowly or drastically changing to grey to dark, suggesting ash presence.
• Drying vegetation, drying streams, and water wells are visual keys
• Crater glow at the summit area is another possible sign.
• Increasing frequency of rolling rocks from the summit and localized landslides not related to heavy rains provide further evidence.
• Summit area glows or becomes incandescent at night
• Auditory clues include rumbling noises.
• Olfactory signs include the smell of sulfur.
• Tactile signs include ground movement or volcanic earthquakes increasingly felt.

Volcano Alert Levels

• Alert Level 0 signifies quite or no alert.
• Monitored parameters are within background levels, level of volcanic earthquakes is unremarkable, and generally weak steam emission are present
• Quiescence, or no magmatic eruption is foreseen.
• Hazards like explosions, rockfalls and landslides that may suddenly occur within the four (4) kilometer radius Permanent Danger Zone (PDZ) exist.
• Alert Level 1 indicates a low level of volcanic unrest.
• Slight increases in volcanic earthquake and steam/gas activity, sporadic explosions from existing or new vents can be observed.
• Notable increase in the temperature of hot springs and slight inflation or swelling of the edifice are clues
• Hydrothermal, magmatic, or tectonic disturbances are present.
• The source of activity is shallow, near crater or in the vicinity of Irosin Caldera
• Entry into the PDZ must be prohibited.
• Alert Level 2 means a moderate level of volcanic unrest.
• Elevated levels of volcanic earthquake, steam/gas emission, ground deformation and hot spring temperature exist.
• Intermittent steam/ash explosion and above baseline Sulfur Dioxide2 (SO2) emission rates are present.
• Increased swelling of volcanic edifice can be observed.
• Probable intrusion of magma at depth, which can lead to magmatic eruption is possible.
• Entry within PDZ must be prohibited, and areas within five (5) kilometers of the active vent may be included in the danger zone.
• Alert Level 3 signifies high level of volcanic unrest.
• Sustained increases in the levels of volcanic earthquakes, some may be perceptible can be observed.
• Low-frequency earthquakes, volcanic tremor, rumbling sounds, and forceful and voluminous steam/ash ejections are present
• Sustained increases in SO2 emission rates, and ground deformation/swelling of the edifice are clues.
• Activity at the summit may involve dome growth and/or lava flow, and resultant rockfall.
• Magma is near or at the surface, and activity could lead to hazardous eruption in weeks.
• Danger zones may be expanded up to eight (8) kilometers from the active crater.
• Alert Level 4 signifies hazardous eruption imminent.
• Intensifying unrest is characterized by earthquake swarms and volcanic tremor, many perceptible.
• Frequent strong ash explosions are possible.
• A sustained increase, or sudden drop, of SO emission can be observed
• Increasing rates of ground deformation and swelling of the edifice, as well as Lava dome growth and/or lava flow increases, with increased frequency and volume of rockfall are clues.
• Magmatic processes or effusive eruption underway, which can progress into highly hazardous eruption.
• Danger Zone is extended up to nine (9) kilometers or more from the active crater.
• Alert Level 5 means that Hazardous Eruption is in Progress.
• Magmatic eruption characterized by explosive production of tall ash-laden eruption columns, or by massive collapses of summit lava domes is occurring.
• Deadly pyroclastic flows, surges and/or lateral blasts and widespread ashfall are possible.
• Life-threatening eruption producing volcanic hazards endanger communities.
• Additional danger areas may be declared as eruption progresses.
• Permanent Danger Zones (PDZ) are delineated and identified areas where no permanent habitation is recommended due to possible impacts of various hazards anytime.