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| Background. During the Holocene, Popocatepetl produced both effusive and pyroclastic activity. About 30 eruptions are known since 1345, although early documentation is poor. Activity in 1920-22 produced intermittent explosive eruptions and a small lava plug in the summit crater. Minor ash clouds were also reported in 1923-24, 1933, 1942-43, and 1947. Popocatepetl has shown increasing levels of activity since 1993. On 21 December 1994 the first major ash emission broke the long quiescence; afterward, low level activity persisted through 1995. On 5 March 1996, the volcano started a new episode of activity similar to that of December 1994. By the end of March 1996 observers saw explosions and a lava dome growing at the crater's bottom. One of the largest explosions, on 30 April 1996, killed five people climbing the volcano. The dome continued to grow slowly until July 1996 but by September 1996 it stopped. Afterwards ash emissions became less frequent, but larger in size, and generally accompanied by major explosions. This trend has been continuing until the present. Information Contacts: Roberto Meli, Roberto Quaas Weppen, Alejandro Mirano, Bertha Lopez J.L. Macias, Instituto de Geofisica, UNAM, Circuito Cientifico C.U. 04510 Mexico D.F., Thomas J. Casadevall, Office of the Regional Director, U.S. Geological Survey, MS 150, 345
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