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Volcano Monitoring (Alert Levels)

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BULUSAN VOLCANO ALERT LEVELSline
Alert LevelCriteriaInterpretation/Recommendation

0

Quiet or

No Alert

All monitored parameters within background levels. Unremarkable level of volcanic earthquakes occurring within the volcano area. Generally weak steam emission.

Quiescence; no magmatic eruption is foreseen. However, there are hazards  (explosions, rockfalls and landslides) that may suddenly occur within the four-kilometer radius Permanent Danger Zone (PDZ).

1

Low Level of Volcanic Unrest

Slight increase in volcanic earthquake and steam/gas activity.  Sporadic explosions from existing or new vents. Notable increase in the temperature of hot springs. Slight inflation or swelling of the edifice.

 Hydrothermal, magmatic, or tectonic disturbances. The source of activity is shallow, near crater or in the vicinity of Irosin Caldera. Entry into the PDZ must be prohibited.

2 

Moderate Level of Volcanic Unrest

Elevated levels of any of the following: volcanic earthquake, steam/gas emission, ground deformation and hot spring temperature.  Intermittent steam/ash explosion and above baseline Sulfur Dioxide (SO2) emission rates. Increased swelling of volcanic edifice.

Probable intrusion of magma at depth, which can lead to magmatic eruption. Entry within PDZ must be prohibited. Other areas within five (5) kilometers of the active vent may be included in the danger zone.

3

High Level of Volcanic Unrest

Sustained increases in the levels of volcanic earthquakes, some may be perceptible.  Occurrence of low-frequency earthquakes, volcanic tremor, rumbling sounds.

Forceful and voluminous steam/ash ejections. Sustained increases in SO2 emission rates, ground deformation/swelling of the edifice. Activity at the summit may involve dome growth and/or lava flow, 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.

4

Hazardous Eruption Imminent		 Intensifying unrest characterized by earthquake swarms and volcanic tremor, many perceptible.  Frequent strong ash explosions.  Sustained increase, or sudden drop, of SO2 emission. Increasing rates of ground deformation and swelling of the edifice. Lava dome growth and/or lava flow increases, with increased frequency and volume of rockfall. Magmatic processes or effusive eruption underway, which can progress into highly hazardous eruption. Danger Zone may be extended up to nine (9) kilometers or more from the active crater.

5

Hazardous Eruption in Progress

Magmatic eruption characterized by explosive production of tall ash-laden eruption columns, or by massive collapses of summit lava dome. Generation of deadly pyroclastic flows, surges and/or lateral blasts and widespread ashfall.

Life-threatening eruption producing volcanic hazards that endanger communities. Additional danger areas may be declared as eruption progresses.

 

1 Lahars may be generated by intense rainfall over the volcano area and may affect riverside communities far down the PDZ.

2 Sulfur Dioxide is a major gas component of magma.

 

STAND-DOWN PROCEDURES

In order to minimize unnecessary changes in declaration of Alert Levels, the following periods shall be observed:

From Level 5 to Level 4:           Wait at least 24 hours after hazardous activity stops

From Level 4 to Level 3 or 2:   Wait at least 2 weeks after activity drops below Level 4

From Level 3 to Level 2:           Wait 2 weeks after activity drops below Level 3

 

Revised 25 September 2014

Posted 08/08/2018mlc

HIBOK-HIBOK VOLCANO ALERT SIGNALSline
Alert LevelCriteriaInterpretation

No Alert

 Background, quiet No eruption in foreseeable future

1

 

 Low level seismic, fumarolic, other unrest. Magmatic, tectonic or hydrothermal disturbance; no eruption imminent.

2 

 

 Low to moderate level of seismic, other unrest  with positive evidence for involvement of magma

Probable magmatic intrusion; could eventually lead to an eruption.

3

 

 Relatively high and increasing unrest, including numerous b-type earthquakes, accelerating ground deformation and rockfalls, increased vigor of fumaroles, gas emission

Increasing likelihood of an eruption, possibly within days to week.

4


 Intense unrest, including harmonic tremor and/or may “long period” (=low frequency) earthquakes or quiet lava emissions and/or dome growth and/or small explosions Magma close to or at earth’s surface.  Hazardous explosive eruption likely, possible within hours to days

5


 Hazardous explosive eruption in progress, with pyroclastic flows, surges and/or eruption column rising at least  6 km or 20,000 feet above sea level Explosive  eruption in progress.  Hazards in valleys and downwind

 

STAND-DOWN PROCEDURES:

In order to protect against “lull before the storm” phenomena, alert levels will be maintained for the following periods AFTER activity decreases to the next lower level:

From level 5 to level 4:            Wait 12 hours after level 5 activity stops

From level 4 to level 3 to 2:    Wait 2 weeks after activity drops below level 4

From level 3 to level 2:            Wait 2 weeks after activity drops below level 3

 

Ashfall will occur from secondary explosions for several years after eruption, whenever rainfall and lahars come in contact with still hot- pyroclastic deposits.  These secondary explosions will occur regardless of alert level.

 

 

Posted 08/08/2018mlc

KANLAON VOLCANO ALERT SCHEMEline
Alert LevelCriteriaInterpretation/Recommendation
0
No Alert (Normal)

All monitored parameters within background levels. Unremarkable level of volcanic earthquakes occurring within the volcano area.

 Quiescence; nno magmatic eruption is foreseen. However, there are perennial hazards (sudden explosions, rockfalls and landslides) within the four (4) kilometer-radius Permanent Danger Zone (PDZ) that may occur suddenly and without warning.

1

Low Level of Volcanic Unrest

 

 Slight increase in volcanic earthquake and steam/gas activity.  Sporadic explosions from the summit crater or new vents. Notable increase in the temperature, acidity and volcanic gas concentrations of monitored springs and fumaroles. Slight inflation or swelling of the edifice.

Hydrothermal, magmatic, or tectonic disturbances may be underway. The source of activity may be shallow, near the summit crater or in the vicinity of the edifice. Entry into the PDZ must be prohibited.

2

Moderate Level of Volcanic Unrest

Elevated levels of any of the following parameters: volcanic earthquake, temperature, acidity and volcanic gas concentrations of monitored springs and fumaroles, steam and ash explosions from the summit crater or new vents, inflation or swelling of the edifice.

 Probable intrusion of magma at depth, which may or may not lead to magmatic eruption. Entry within PDZ must be prohibited.

3

High Level of Volcanic Unrest

 Sustained increases in the levels of volcanic earthquakes, some of which may be perceptible.  More energetic and frequent steam/ash explosions. Sustained increases in the temperature, acidity and volcanic gas concentrations of springs and fumaroles, and in the levels of ground deformation or swelling of the edifice. Activity at the summit may involve sluggish lava extrusion with resultant rockfall.

Magmatic intrusion to shallow levels of the edifice is driving unrest, with indications that hazardous eruption could occur in weeks. Danger zones may be expanded to a radius of six (6) kilometers from the summit crater or active vent.

4

Hazardous

Eruption Imminent

 Intensifying unrest characterized by earthquake swarms and volcanic tremor, many of which may be perceptible.  Frequent strong ash explosions. Increasing rates of ground deformation and swelling of the edifice. Increasing rates of lava extrusion with increased frequency and volume of rockfall and volcanic gas flux, or abrupt decrease in volcanic gas flux due to plugging of lava at the summit crater or active vent.

Low-level magmatic eruption underway, which can progress to highly hazardous major eruption within hours or days. Danger zones may be expanded to a radius of ten (10) kilometers or more from the summit crater or active vent.

5

Hazardous Eruption in Progress

Magmatic eruption characterized by explosive production of tall ash-laden eruption columns, and/or descent and frequent failure of voluminous lava flows. Generation of deadly pyroclastic flows, surges and/or lateral blasts and widespread tephra fall (ashfall). Lahars generate along river channels.

Life-threatening major eruption producing volcanic hazards that endanger communities. Danger zones may be expanded to fourteen (14) kilometers as eruption progresses.

STAND-DOWN PROCEDURES

In order to minimize unnecessary changes in declaration of Alert Levels, the following periods shall be observed:

From Level 5 to Level 4:            Wait at least 24 hours after hazardous activity stops

From Level 4 to Level 3 or 2:    Wait at least 2 weeks after activity drops below Level 4

From Level 3 to Level 2:            Wait 2 weeks after activity drops below Level 3

 

 

Revised  March 2016

Posted 08/08/2018mlc

MAYON VOLCANO ALERT SIGNALSline
Alert LevelMain CriteriaInterpretation/Recommendations
0
No Alert		 Quiet. All monitored parameters within background levels. No eruption in foreseeable future. Entry in the 6-km radius Permanent Danger Zone (PDZ) is not advised because phreatic explosions and ash puffs may occur without precursors.

1

Abnormal

 Low level unrest. Slight increase in seismicity. Slight increase in SO2 gas output above the background level. Very faint glow of the crater may occur but no conclusive evidence of magma ascent. Phreatic explosion or ash puffs may occur. No eruption imminent. Activity may be hydrothermal, magmatic or tectonic in origin. No entry in the 6-km radius PDZ.
2
Increasing Unrest		 Moderate unrest. Low to moderate level of seismic activity. Increasing SO2 flux. Faint/intermittent crater glow. Swelling of edifice may be detected. Confirmed reports of decrease in flow of wells and springs during rainy season. Unrest probably of magmatic origin; could eventually lead to eruption. 6-km radius Danger Zone may be extended to 7 km in the sector where the crater rim is low.
3
Increased Tendency Towards Hazardous Eruption		 Relatively high unrest. Volcanic quakes and tremor may become more frequent. Further increase in SO2 flux. Occurrence of rockfalls in summit area. Vigorous steaming / sustained crater glow. Persistent swelling of edifice. Magma is close to the crater. If trend is one of increasing unrest, eruption is possible within weeks. Extension of Danger Zone in the sector where the crater rim is low will be considered.

4
Hazardous

Eruption
Imminent		 Intense unrest. Persistent tremor, many “low frequency”-type earthquakes. SO2 emission level may show sustained increase or abrupt decrease. Intense crater glow. Incandescent lava dome, lava fountain, lava flow in the summit area. Hazardous eruption is possible within days. Extension of Danger zone to 8 km or more in the sector where the crater rim is low will be recommended.

5
Hazardous

Eruption		 Hazardous eruption ongoing. Occurrence of pyroclastic flows, tall eruption columns and extensive ashfall. Pyroclastic flows may sweep down along gullies and channels, especially along those fronting the low part(s) of the crater rim. Additional danger areas may be identified as eruption progresses. Danger to aircraft, by way of ash cloud encounter, depending on height of eruption column and/or wind drift.

 

 

Revised 14 January 2018

Posted 08/08/2018mlc

TAAL VOLCANO ALERT LEVEL SCHEME

As of June 2021line

 

The PHIVOLCS Volcano Alert Level Scheme is a reference guide to understanding the state of an active volcano, the current level of threat it poses and the steps that are needed to be taken to ensure public safety. ALERT LEVEL represents the overall condition of the volcano, with Alert Levels 1 to 5 corresponding to increasing severity of unrest. MONITORING CRITERIA are parameters from instrumental, visual and other sensory observations of the volcano that are primarily acquired by on-site Volcano Observatories and scientific surveys. INTERPRETATION explains the probable processes taking place within the volcano based on monitoring criteria and the potential dangers that may arise from these processes. RECOMMENDATIONS are response measures that must be followed by the public and implemented by local and national government units to ensure that populations are kept out of harm’s way. STEP-DOWN CRITERIA are conditions that need to be met before the Alert Level is brought down to the next level.

 

Alert Level

(Step-up)

Monitoring CriteriaInterpretationRecommendationsStep-down Criteria

Alert Level

(Step-down)

0

NORMAL

 Background parameters: Volcanic earthquakes typically <5/day; Main Crater Lake gas (diffuse CO2) emission within 1,000 tonnes/day, average water temperature <35ºC and acidity >pH2.5; General stationary or deflationary trends in ground deformation. Quiescence; no major eruption in foreseeable future, but steam-driven and gas eruptions can occur without warning. Permanent habitation on Taal Volcano Island (TVI) must not be allowed.  

0

NORMAL

1

LOW-LEVEL UNREST

 Abnormal parameters: Moderate level of seismic activity with some felt events; Main Crater Lake gas (diffuse CO2) emission >1,000 tonnes/day, slight increases in fumarole and/or Main Crater Lake temperatures and acidity; Slight and/or localized inflationary ground deformation changes in TVI. Hydrothermal or tectonic activity beneath the volcano may be occurring; steam-driven, gas or hydrothermal explosions can occur without warning. Entry into the TVI Main Crater, the Daang Kastila fissure area and the Mt. Tabaro eruption site must not be allowed. Alert Level 1 monitoring criteria have been in decline for at least one (1) month before lowering to Alert Level 0.

1

LOW-LEVEL UNREST

2

INCREASING UNREST

 Increasing changes in parameters: Elevated level of seismic activity with some felt events in TVI and Taal Caldera (TC); Occurrence of earthquake swarms and low-frequency events; Sustained increases in inflationary ground deformation including ground tilt in TVI; Slight positive microgravity changes in TVI and TC; Increasing fumarole temperature and acidity and upwelling in the Main Crater Lake; Significant increases in CO2 emission, instrumental detection of airborne SO2 >500 tonnes/day. Shallow hydrothermal unrest and/or deep-seated magmatic intrusion may be occurring, bringing higher chances of steam-driven, gas or hydrothermal explosions. Entry into TVI must not be allowed. Communities in pre-defined areas of the highest hazard must ready for possible evacuation. Alert Level 2 monitoring criteria have been in decline for one (1) month before lowering to Alert Level 1. 2
DECREASED UNREST

3
INTENSIFIED UNREST/ MAGMATIC UNREST

 Intensifying changes in parameters: Sudden increase or decline in seismic activity; Perceptible earthquakes, occurrence of swarms of volcano-tectonic and/or hybrid earthquakes; Elevating SO2 flux; Significant changes in Main Crater Lake temperature and/or acidity; Accelerating increase in ground inflation, rapid increase in ground tilt in TVI; Precursory phreatic or weak phreatomagmatic eruptions commence. Magmatic or explosive phreatomagmatic eruption is imminent; precursory eruptive activity may be taking place and generating ashfall, ballistics and/or short lava flows. TVI, Taal Lake and pre-defined lakeshore communities of Batangas facing the active vent must be evacuated. Alert Level 3 monitoring criteria have been in decline for at least two (2) weeks before lowering to Alert Level 2. 3
DECREASED TENDENCY TOWARDS HAZARDOUS ERUPTION

4

HAZARDOUS ERUPTION IMMINENT

 Accelerating changes or abrupt decline in parameters: Rapidly intensifying volcanic earthquakes, continuous volcanic tremor, frequent felt earthquakes; Profuse degassing or ash explosions along existing or new vents and fissures; Elevated and/or sudden drop in SO2 flux; Accelerating increase or reversal of ground deformation patterns and ground fissuring; Explosive eruption or lava effusion with or without volcanic lightning commence. Strong phreatomagmatic or magmatic eruption is taking place, which may or may not lead to violently explosive eruption. Widespread ashfall and ballistics, lava flows and minor pyroclastic density currents (PDCs) on TVI may be generated. Communities in pre-determined worst-case or scenario-based volcanic hazards zones must be evacuated. Alert Level 4 monitoring criteria have been in decline for two (2) weeks before lowering to Alert Level 3. 4
DECREASED TENDENCY TOWARDS HIGHLY HAZARDOUS ERUPTION

5
HIGHLY
HAZARDOUS ERUPTION IN PROGRESS

 

 Violently explosive magmatic eruption ongoing: Continuous intense seismic activity, including explosion-type volcanic earthquakes and strong felt events; Sustained tall eruption column with expansive umbrella cloud accompanied by loud booming sounds and volcanic lightning; Generation of PDCs/base surges and volcanic tsunami that transport across Taal Lake and lakeshore towns; Ground fissuring and large-particle tephra fall impacting lakeside communities and ashfall impacting farther areas. Plinian/ Subplinian/ Violent phreatomagmatic eruption is taking place. Extreme life-threatening hazards of base surges/PDCs, volcanic tsunami, thick tephra fall/ashfall, fissuring, lahars and landslides could impact communities around the lake and downwind of the eruption plume. Additional areas for evacuation should be considered based on prevailing conditions. Alert Level 5 conditions have ceased for at least 24 hours before lowering to Alert Level 4.  

 


Revised 23 June 2021

Posted 07/05/2021 mlc, kvcs

PINATUBO VOLCANO ALERT LEVEL SCHEME

As of June 2021line

 

The PHIVOLCS Volcano Alert Level Scheme is a reference guide to understanding the state of an active volcano, the current level of threat it poses and the steps that are needed to be taken to ensure public safety. ALERT LEVEL represents the overall condition of the volcano, with Alert Levels 1 to 5 corresponding to increasing severity of unrest. MONITORING CRITERIA are parameters from instrumental, visual and other sensory observations of the volcano that are primarily acquired by on-site Volcano Observatories and scientific surveys. INTERPRETATION explains the probable processes taking place within the volcano based on monitoring criteria and the potential dangers that may arise from these processes. RECOMMENDATIONS are response measures that must be followed by the public and implemented by local and national government units to ensure that populations are kept out of harm’s way. STEP-DOWN CRITERIA are conditions that need to be met before the Alert Level is brought down to the next level.

 

Alert LevelMonitoring CriteriaInterpretationRecommendationsStep-down CriteriaAlert Level (Step-down)

0

NORMAL

 Background parameters: Volcanic earthquakes typically <5/day; Caldera lake CO2 flux <1000 tonnes/day.
 Quiescence; no major eruption in foreseeable future. Communities at risk must continue preparedness efforts.  

0

NORMAL

1

LOW-LEVEL UNREST

 Abnormal parameters: Volcanic earthquake clusters along regional faults or lineaments or within the hydrothermal system; Changes in fumarolic activity in the crater; increased crater lake CO2 flux and CO2/H2S ratio changes. Hydrothermal or local tectonic activity beneath/near the volcano may be occurring; no eruption imminent. Extreme caution when venturing into the Pinatubo Caldera recommended. AL 1 monitoring criteria have been in decline for at least one (1) month before lowering to AL 0. 1
LOW-LEVEL UNREST

2

INCREASING UNREST

 Increasing changes in parameters: Increased and shallowing high-frequency (HF) or volcano-tectonic (VT) earthquake clusters, shallow sporadic low-level tremor with long-period (LP) or low-frequency (LF) events, DLPs (deep long period) events at sub-crustal depths; Continued increases in crater lake CO2 flux and CO2/H2S ratios, significant SO2 emission may be detected; Increased fumarolic activity with discrete weak phreatic eruptions; Ground deformation detected by satellite systems. Deep-seated magmatic intrusion and/ or increased hydrothermal activity may be occurring, with increased chances of phreatic, gas or hydrothermal explosions; could eventually lead to an eruption. No entry into Pinatubo Caldera; Preparation of communities in case of escalation of unrest. AL 2 monitoring criteria have been in decline for one (1) month before lowering to AL 1. 2
DECREASED UNREST

3

INTENSIFIED UNREST

 Intensifying changes in parameters: VT/ HF earthquake clusters or swarms within shallow depths of the edifice, increase in the intensity and duration of LP/LF events, DLP clusters at lower crustal depths; Sustained or increasing SO2 emission, increased phreatic activity with explosion-type earthquakes or tremor episodes; Increasing ground deformation or inflation of the edifice. Certain magmatic intrusion into the shallow magma system or edifice, with higher chances of a major eruption; precursory eruptive activity due to disruption of the hydrothermal system; lava dome growth may occur.
 Evacuation of upland communities up to 10-kilometers from the summit caldera. AL 3 monitoring criteria have been in decline for at least two (2) weeks before lowering to AL 2. 3
DECREASED TENDENCY TOWARDS HAZARDOUS ERUPTION

4
HIGHLY HAZARDOUS ERUPTION IMMINENT

 Accelerating changes or abrupt decline in parameters: Strong VT/ HF earthquakes within a few kilometers depth of the edifice with felt intensities, episodic swarms of hybrid or LP earthquakes, episodic tremor with continuous ash emission, sustained and intensifying volcanic tremor, episodic explosion earthquakes with explosive activity; Increasing incidence and magnitudes of volcanic earthquakes; Successive explosions with pronounced eruption columns and small-volume pyroclastic density currents (PDCs); Intense ground deformation or bulging of the summit region; Abrupt increase or drop in SO2/volcanic gas flux. Phreatomagmatic or pre-climactic magmatic eruption; If magma ascent rates increase, highly explosive eruption probable within hours to a few days; if magma ascent rates decrease, prolonged lava dome growth may occur. Evacuation of communities within pre-determined hazard zones for PDCs, heavy ashfall and syn-eruption lahars. AL 4 monitoring criteria have been in decline for two (2) weeks before lowering to AL 3. 4
DECREASED TENDENCY TOWARDS HIGHLY HAZARDOUS ERUPTION

5
HIGHLY
HAZARDOUS ERUPTION IN PROGRESS

 Highly explosive magmatic eruption ongoing: Successive explosion-type earthquakes or large-amplitude volcanic tremor and VT earthquakes; Successive or sustained explosions with large eruption column and pronounced umbrella cloud that could exceed 20-kilometer heights above the crater; extensive PDCs emplaced around the edifice; widespread ashfall; syn-eruption lahars. Climactic Subplinian to Plinian eruption; Volcanic hazards expected within 30-kilometer radius of the crater and downwind of the eruption plume. Evacuation of additional communities, downwind of the eruption plume, along major river systems and in buffer extensions of hazard zones. AL 5 conditions have ceased for at least 24 hours before lowering to AL 4.  

 

Revised 21 June 2021

Revised 21 June 2021Posted 07/05/2021 mlc, ks

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