Global Volcanism Program

29 June-5 July 2011

PHIVOLCS reported that during the previous 11 weeks, since the Alert Level for Taal was raised to 2 (on a scale of 0-5) on 9 April, the number of earthquakes recorded daily gradually declined, hydrothermal activity abated, carbon dioxide gas emissions decreased, ground temperature and total magnetic field measurements in the main crater showed no significant changes, and deformation data showed no signs of increasing pressure. On 5 July the Alert Level was lowered from 2 to 1.

Sources: Philippine Institute of Volcanology and Seismology (PHIVOLCS)

Available Weekly Reports

29 June 2011 Back to Top

PHIVOLCS reported that during the previous 11 weeks, since the Alert Level for Taal was raised to 2 (on a scale of 0-5) on 9 April, the number of earthquakes recorded daily gradually declined, hydrothermal activity abated, carbon dioxide gas emissions decreased, ground temperature and total magnetic field measurements in the main crater showed no significant changes, and deformation data showed no signs of increasing pressure. On 5 July the Alert Level was lowered from 2 to 1.

Sources: Philippine Institute of Volcanology and Seismology (PHIVOLCS)

25 May 2011 Back to Top

PHIVOLCS reported that field measurements conducted on 24 May at the E sector inside Taal's Main Crater Lake showed that the water temperature slightly increased from 32.5 to 32.8 degrees Celsius, the pH value became more slightly acidic decreasing from 2.83 to 2.67, and the water level increased by 4 cm. During 25-29 May, between 6 and 10 daily volcanic earthquakes were detected by the seismic network. Some of the earthquakes were felt by nearby residents on the SE part of the island. During 29-30 May, 115 earthquakes were recorded. Twelve of these events were felt at Intensity I-IV by residents of Pira-piraso, Alas-as, and Calauit located in the NE, SW, and SE sectors of Volcano Island, respectively. During 30-31 May there were 31 earthquakes noted. The Alert Level remained at 2 (on a scale of 0-5).

Sources: Philippine Institute of Volcanology and Seismology (PHIVOLCS)

20 April 2011 Back to Top

During 12-19 April, PHIVOLCS reported that between 6 and 19 daily volcanic earthquakes at Taal were detected by the seismic network. Some of the earthquakes were felt by nearby residents on the SE part of the island. The Alert Level remained at 2 (on a scale of 0-5).

Sources: Philippine Institute of Volcanology and Seismology (PHIVOLCS)

13 April 2011 Back to Top

During 12-19 April, PHIVOLCS reported that between 6 and 21 daily volcanic earthquakes at Taal were detected by the seismic network. Some of the earthquakes were felt by nearby residents. Results of a ground deformation survey conducted around Volcano Island during 5-11 April showed that the edifice was slightly inflated compared to a survey from early February. The Alert Level remained at 2 (on a scale of 0-5). According to news articles, the number of people that had evacuated from around Taal rose to 1,375.

Sources: Philippine Institute of Volcanology and Seismology (PHIVOLCS) , Agence France-Presse (AFP)

6 April 2011 Back to Top

PHIVOLCS reported that field observations of Taal conducted at the E sector inside the main crater lake on 5 April 2011 showed that steaming at the thermal area was weak. The water level had receded 3 mm and the water temperature slightly increased from 30 to 30.5 degrees Celsius. Since the previous measurement on 29 March, the pH value increased indicating that the water had become slightly less acidic. Gas measurements conducted last January, February, and March yielded carbon dioxide emission values (in tonnes per day) of 2,250, 1,875, and 4,670, respectively.

On 9 April PHIVOLCS noted that after 31 March the number of earthquakes gradually rose and the depths become more shallow (1-4 km). Steaming at the N and NE sides of the main crater occasionally intensified and was occasionally accompanied by hissing sounds. The Alert Level was raised to 2 (on a scale of 0-5) because of increased seismicity and carbon dioxide emissions. PHIVOLCS warned tourists and residents to avoid Volcano Island. According to news articles, about 100 families had volunteered to evacuate; about 7,000 people remained.

Sources: Philippine Institute of Volcanology and Seismology (PHIVOLCS) , Philippine Daily Inquirer

26 January 2011 Back to Top

During 25-27 and 29-30 January, PHIVOLCS reported that up to six volcanic earthquakes at Taal were detected daily by the seismic network. Field observations during 23-25 January revealed an increase in the number of steaming vents inside Main Crater and a drop in the lake level. The lake water temperature and pH values were normal. Visual observations on 27 January showed that steaming at a thermal area in the crater was weak. The Alert Level remained at 1 (on a scale of 0-5).

Sources: Philippine Institute of Volcanology and Seismology (PHIVOLCS)

19 January 2011 Back to Top

PHIVOLCS reported that field observations of Taal on 18 January revealed steam rising from the thermal area inside the Main Crater. Temperature and acidity of the lake were at normal levels, and the color had not changed. During 18-25 January, up to seven daily volcanic earthquakes were detected by the seismic network. The Alert Level remained at 1 (on a scale of 0-5).

Sources: Philippine Institute of Volcanology and Seismology (PHIVOLCS)

12 January 2011 Back to Top

PHIVOLCS reported that a deformation survey of Taal conducted in December 2010 showed slight inflation as compared to a survey conducted in September 2010. Field observations on 10 January revealed no significant changes. Weak steaming from a thermal area inside the main crater was noted and the lake temperature and color were normal. During 15-16 January 10 volcanic earthquakes were detected; two earthquakes were felt by residents in barangay (neighborhood) Pira-piraso, on the N side of the island. On 17 January three volcanic earthquakes were detected and on 18 January only one was reported. The Alert Level remained at 1 (on a scale of 0-5).

Sources: Philippine Institute of Volcanology and Seismology (PHIVOLCS)

28 July 2010 Back to Top

PHIVOLCS reported observations during the previous eight weeks after the Alert Level for Taal was raised to 2 (scale is 0-5, with 0 referring to No Alert status) on 8 June. Temperature measurements of the main crater lake did not increase further since 8 June, remaining between 330 and 340 degrees Celsius. The number of earthquakes recorded daily gradually declined to background levels beginning the second week of July. Hydrothermal activity in the N and NE sides of the main crater and Daang Kastila also decreased. Precise leveling measurements conducted during 13-21 July along the NE, SE, and SW flanks detected minimal inflation. On 2 August, PHIVOLCS lowered the Alert Level to 1.

Sources: Philippine Institute of Volcanology and Seismology (PHIVOLCS)

2 June 2010 Back to Top

On 8 June, PHIVOLCS raised the Alert Level for Taal to 2 (scale is 0-5, 0 referring to No Alert status) due to changes in several monitored parameters, starting in late April. Since 26 April the number of earthquakes per day continued to increase, as well as the magnitude. Low-frequency volcanic earthquakes were detected on 2 June, and during the previous day high-frequency earthquakes were noted. In addition to increased seismicity, the temperature of the Main Crater Lake increased from 32 degrees Celsius on 11 May to 34 degrees Celsius on 24 May. Steaming from the N and NE sides of Main Crater occasionally intensified. Deformation data had shown slight inflation since 2004; measurements taken at the SE side of Taal on 7 June showed further inflation by 3 mm.

Sources: Philippine Institute of Volcanology and Seismology (PHIVOLCS)

27 August 2008 Back to Top

PHIVOLCS reported ongoing seismic unrest at Taal on 28 August. Ten earthquakes occurred; two at Intensity II were felt by residents in the Pira-Piraso village and were accompanied by rumbling sounds. The earthquakes were located NE of the island near the Daang Kastila area at estimated depths of 0.6-0.8 km. Surface observations indicated no change in the main crater lake area. PHIVOLCS warned that the main crater was off-limits to the general public. The Alert Level remained at 1 (scale is 0-5, 0 referring to No Alert status).

Sources: Philippine Institute of Volcanology and Seismology (PHIVOLCS)

22 November 2006 Back to Top

According to news articles, geysers of muddy water 3-5 m high occurred in the NNE portion of Taal's main crater during 17-21 November. On 24 November, a new episode of 50-cm-high geyser activity and increased seismicity prompted PHIVOLCS to raise the Alert Level from 1 to 2.

Sources: Xinhua , Associated Press

4 October 2006 Back to Top

PHIVOLCS reported ongoing seismic unrest at Taal on 26 September. During 25-26 September, 29 volcanic earthquakes occurred with five felt Modified Mercalli intensities of II to III. Epicenters were dispersed NE, N, and NW. Approximately five seismic events in a 24-hour period is typical during quiet periods.

Sources: Philippine Institute of Volcanology and Seismology (PHIVOLCS)

27 October 2004 Back to Top

PHIVOLCS raised the Alert Level at Taal from 0 to 1 (on a scale of 0-5) on 29 October due to an increase in seismicity at the volcano. The seismic network at Taal began to record significant volcanic earthquakes on 23 September. In general, through 29 October the number of earthquakes increased, with a maximum of 13 earthquakes recorded on 15 October. Initial epicenter locations were in the vicinity of Main Crater and to the NNW near Binintiang Malaki and to the SSE near Calauit. No significant changes in thermal and steam emissions were observed. PHIVOLCS recommended appropriate vigilance by the public when visiting the island and noted that Main Crater was off-limits to visitors because of the potential for sudden steam explosions and high concentrations of noxious gases.

Sources: Philippine Institute of Volcanology and Seismology (PHIVOLCS)

Summary of eruption dates and Volcanic Explosivity Indices (VEI).

Start Date	Stop Date	Eruption Certainty	VEI	Evidence	Activity Area or Unit
1977 Oct 3	1977 Nov 12 (?)	Confirmed	2	Historical	SW flank (near Mt. Tabaro)
1976 Sep 3	1976 Oct 17	Confirmed	2	Historical	SW flank (near Mt. Tabaro)
1970 Nov 9	1970 Nov 13	Confirmed	1	Historical	SW flank (near Mt. Tabaro)
1969 Oct 29	1969 Dec 10	Confirmed	2	Historical	SW flank (near Mt. Tabaro)
1968 Jan 31	1968 Apr 2	Confirmed	2	Historical	SW flank (near Mt. Tabaro)
1967 Aug 16	1967 Aug 19	Confirmed	1	Historical	SW flank (near Mt. Tabaro)
1966 Jul 5	1966 Aug 4	Confirmed	2	Historical	SW flank (near Mt. Tabaro)
1965 Sep 28	1965 Sep 30	Confirmed	4	Historical	SW flank (near Mt. Tabaro)
1911 Jan 27	1911 Feb 8	Confirmed	2	Historical
1904 Apr	1904 Jul 15 ± 5 days	Confirmed	1	Historical	Base of south wall of main crater
1903 Apr	Unknown	Confirmed	2	Historical
[ 1885 ]	[ Unknown ]	Uncertain
1878 Nov 12	1878 Nov 15	Confirmed	2	Historical
1874 Jul 19	Unknown	Confirmed	2	Historical
1873	Unknown	Confirmed	2	Historical
1842	Unknown	Confirmed	2	Historical
1825	Unknown	Confirmed	2	Historical
1808 Feb	1808 Apr	Confirmed	2	Historical
1790	Unknown	Confirmed	2	Historical
1754 May 15	1754 Dec 4	Confirmed	3	Historical	Summit crater and SE flank
1749 Aug 11 (?)	1749 Sep	Confirmed	4	Historical
1731	Unknown	Confirmed	2	Historical	Pira-piraso (NE flank)
1729	Unknown	Confirmed	2	Historical	Binintiang Munti
1716 Sep 24	1716 Sep 27	Confirmed	4	Historical	Calauit (sublacustral SE flank)
1715	Unknown	Confirmed	2	Historical	Binintiang Malaki
1709	Unknown	Confirmed	2	Historical	Binintiang Munti
1707	Unknown	Confirmed	2	Historical	Binintiang Malaki
1645	Unknown	Confirmed	3	Historical
1641	Unknown	Confirmed	3	Historical
1635	Unknown	Confirmed	3	Historical
1634	Unknown	Confirmed	3	Historical
1608 ± 3 years	Unknown	Confirmed	2	Historical
1591	Unknown	Confirmed	3	Historical
1572	Unknown	Confirmed	3	Historical
3580 BCE ± 200 years	Unknown	Confirmed	6	Radiocarbon (uncorrected)	Taal Scoria Flow

Taal volcano is one of the most active volcanoes in the Philippines and has produced some of its most powerful historical eruptions. In contrast to Mayon volcano, Taal is not topographically prominent, but its prehistorical eruptions have greatly changed the topography of SW Luzon. The 15 x 20 km Talisay (Taal) caldera is largely filled by Lake Taal, whose 267 sq km surface lies only 3 m above sea level. The maximum depth of the lake is 160 m, and several eruptive centers lie submerged beneath the lake. The 5-km-wide Volcano Island in north-central Lake Taal is the location of all historical eruptions. The island is a complex volcano composed of coalescing small stratovolcanoes, tuff rings, and scoria cones that has grown about 25% in area during historical time. Powerful pyroclastic flows and surges from historical eruptions of Taal have caused many fatalities.