Philippine Standard Time
 
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Alert Level

Criteria

Interpretation

0

Background, quiet No eruption in foreseeable future.

1

Low level seismicity, fumarolic, other activity

Magmatic, tectonic or hydrothermal disturbance; no eruption imminent.

2

Low to moderate level of seismicity, persistence of local but unfelt earthquakes. Ground deformation measurements above baseline levels. Increased water and/or ground probe hole temperatures, increased bubbling at Crater Lake.

A) Probable magmatic intrusion; could eventually lead to an eruption.

B) If trend declines, volcano may soon go to level 1

3

Relatively high unrest manifested by seismic swarms including increasing occurrence of low frequency earthquakes and/or harmonic tremor (some events felt). Sudden or increasing changes in temperature or bubbling activity or radon gas emission or crater lake pH. Bulging of the edifice and fissuring may accompany seismicity

A) If trend is one of increasing unrest, eruption is possible within days to a few weeks.

B) If trend is one of decreasing unrest, volcano may soon go to level 2

4

Intense unrest, continuing seismic swarms, including harmonic tremor and/or “low frequency earthquakes” which are usually felt, profuse steaming along existing and perhaps new vents and fissures.

Hazardous explosive eruption is possible within days.

5

Base surges accompanied by eruption columns or lava fountaining or lava flows.

Hazardous eruption in progress. Extreme hazards to communities west of the volcano and ashfalls on downwind sectors.

Asof4August2014

 

Alert Leve

Main Criteria

Interpretation/ 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 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.

 

Alert Level

Criteria

Interpretation/ Recommendations

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 1 (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 Dioxide2 (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.
Extension of Danger zone to 8 km or more in the sector where the crater rim is low will be recommended.

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.

 

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


BULUSAN VOLCANO OBSERVATORY
Bgy. Cabid-an, Sorsogon City
Contact No: 09293006416
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.
Revised 25 September 2014.

 

Alert Level

Criteria

Interpretation

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 witin 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


NOTE:
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.

 

Alert Level

Criteria

Interpretation

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, increased vigor of fumaroles, gas emission Increasing likelihood of an eruption, possibly witin 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 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

 

NOTE:
Ashfall will occur from secondary explosions for several years after the 1991 Plinian (calderagenic) eruption, whenever rainfall and lahars come in contact with still hot-hot 1991 pyroclastic flow deposits. These secondary explosions will occur regardless of alert level.

 

Alert Level

Criteria

Interpretation/Recommendations

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 is 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 the surface 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, or plugging of lava at the summit crater or active vent. Low-level magmatic eruption underway, which can progress to highly hazardous major eruption. 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 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


KANLAON VOLCANO OBSERVATORY
Bgy. Cubay, La Carlota City, Negros Occidental; Brgy. Pula, Canlaon City, Negros Oriental
Contact Nos: 09152854895
Revised November 2015