The last report on Popocatépetl covered the period December 2004-January 2005 (BGVN 30:01). This report covers the rest of 2005 (February-December) and comes from the Mexican group Centro Nacional de Prevención de Desastres (CENAPRED).

The volcano has been relatively quiet with daily, low-intensity exhalations of steam and gas sometimes containing minor ash. Some highlights of the reporting interval follow (both in text and in tables), essentially a list of ash-bearing eruptions that usually rose 1-3 km above the crater rim. On 1 December an ash plume rose 5 km.

At 0723 on 13 July an exhalation of moderate intensity produced an ash emission that reached 2 km above the level of the crater. Reports were received of ash fall in Yecapixtla and Ocuituco in the state of Morelos, respectively ~ 30 and ~ 23 km SW of the volcano.

At 0906 on 21 July an exhalation of moderate intensity followed a tremor of high frequency and produced an ash emission that reached 2 km.

At 0313 on 29 July, a moderate exhalation with an explosive component occurred, throwing incandescent fragments onto the E side of the cone, out to a distance of about 1 km. The duration of the intense phase was ~ 1 minute; it was preceded by high-frequency tremor, the same signal was observed for 15 minutes after the explosion. The height of the steam, gas, and ash plume was estimated at 2 km. There were no reports mentioning ash fall.

At 0614 on 29 July a new exhalation with explosive component occurred producing an ash column ~ 2.5 km above the crater. The winds directed the plume NW. The duration of the intense phase was 30 seconds followed by high-frequency tremor (4 minutes). Reports of ashfall in the Milpa Alta area (SE of Mexico City) were received.

At 0819 on 30 July high-frequency tremor started, associated with an ash column. The plume reached 2 km and was directed NW. The emission continued in its most intense phase until 0845. On 2 August at 1247 an exhalation of moderate intensity produced an ash emission that reached 2 km.

At 0305 on 24 October an exhalation of moderate intensity occurred. It was followed by a tremor of high-frequency. The resulting ash plume reached 1.2 km and traveled NE.

At 0653 on 1 December a moderate exhalation sent an ash column to a height of 5 km above the summit, the highest reported ash column in 2005. It was dispersed towards the ENE. The intense episode lasted 2 minutes and was followed by high-frequency tremor lasting 30 minutes. A small ash fall was reported in Amecameca and a warning was issued noting that minor ash fall could occur within the next few hours in Tlaxcala and Puebla states. At 0920 another, smaller eruption produced an ash column 2.5 km above the crater, which also blew ENE.

An eruption that occurred at 1653 on 4 December resulted in reports of ash fall in the states of Tlaxcala and Puebla.

At 2225 on 13 December an explosion at Popocatépetl ejected incandescent fragments over its SE flanks. The explosion lasted ~ 1 minute and was followed by 30 minutes of tremor. The explosion produced a 2.5 km ash column carried by winds to the SE. After the explosion, the volcano returned to its previous low level of activity.

At 0457 on 18 December a small explosion was detected at the Popocatépetl. This event produced an ash column that reached 2.5 km over the summit. The plume traveled towards the NE. The explosion lasted ~ 1 minute and was followed by 8 minutes of high-frequency tremor.

At 0447 on 25 December a moderate exhalation with a minor explosive component occurred. Some incandescent fragments fell on the E side of the cone extending 700 m from the crater edge. The accompanying ash column reached a height of about 3 km moving ENE. The total duration of seismicity associated with this event was nearly 3 minutes, of which 50 seconds corresponded to the intense phase. There were no reports of resulting ash fall.

All of the reported ash-producing events for the February-December 2005 reporting interval are listed in table 16. Table 17 contains the reported earthquakes.

Table 16. Discharges at Popocatépetl during February-December 2005. Courtesy of CENAPRED.

Table 17. Earthquakes at Popocatépetl during February-December 2005. "Below" refers to earthquakes below or in the edifice. Courtesy of CENAPRED.

Geological Summary. Volcán Popocatépetl, whose name is the Aztec word for smoking mountain, rises 70 km SE of Mexico City to form North America's 2nd-highest volcano. The glacier-clad stratovolcano contains a steep-walled, 400 x 600 m wide crater. The generally symmetrical volcano is modified by the sharp-peaked Ventorrillo on the NW, a remnant of an earlier volcano. At least three previous major cones were destroyed by gravitational failure during the Pleistocene, producing massive debris-avalanche deposits covering broad areas to the south. The modern volcano was constructed south of the late-Pleistocene to Holocene El Fraile cone. Three major Plinian eruptions, the most recent of which took place about 800 CE, have occurred since the mid-Holocene, accompanied by pyroclastic flows and voluminous lahars that swept basins below the volcano. Frequent historical eruptions, first recorded in Aztec codices, have occurred since Pre-Columbian time.

Information Contacts: Centro Nacional de Prevención de Desastres (CENAPRED), Av. Delfín Madrigal No.665. Coyoacan, México D.F. 04360, México (URL: https://www.gob.mx/cenapred/).