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43 ~ ~ ~ ~ " ~ ~ ~ z ~ < large populations have settled in the hazard zones. Among the hazards of volcanic activity are the deposition of ashes - such as buried the city of Pompeii - lava flows, landslides, mudflows, and rock falls. Pyroclastic flows and surges, which claimed 29,000 lives in the eruption of Mount Pele in Martinique in 1902 and 2,000 lives around EI Chichon in Mexico in 1982, are particularly lethal. These density currents of extremely hot gases and particles flow down the slopes of a volcano at tens to hundreds of meters per second and cover hundreds of square kilometers. Because of their suddenness and speed, pyroclastic flows and surges are difficult to escape; within minures of their initiation, they can engulf towns and villages. Mudflows account for at least 10 percent of all volcano-related deaths. They are flowing masses of volcanic debris mixed with water. The water may be derived from a volcano's icecap: a rela- tively minor eruption of snow-clad Nevado del Ruiz in 1985 triggered lahars that killed more than 22,000 in Colombia. Very large eruptions may also have long-term effects, including climate change and agricultural disruption. The large explosive eruption of Tam- bora in Indonesia in 1815 caused a major cooling of the Northern Hemisphere and brought on the "year without summer." The ash fall from the eruption so curtailed local food production that a famine occurred, claiming 80,000 lives on Sum- bawa and Lombok Islands. An indirect effect of volcanic activity is the accumulation of volcanic gases in deep crater lakes. Sudden release of these gases can be catastrophic: gas releases from Lake Monoun and Lake Nyos in Cameroon in 1984 and 1986, respectively, claimed 1,800 lives. Advances in understanding volcanoes and their hazards permit the identification of potentially hazardous areas near volcanoes and prediction of certain types of volcanic activity. Potential hazards can be assessed through geologic study and historical review of a volcano's activity. The assessments are useful primarily in forecasting the kinds, scales, and likelihood of activity, bnt are of little value in predicting the timing of future eruptions. The prediction of volcanic eruptions can be achieved on the basis of geophysical and geochemical volcano monitoring. Such prediction relies on detecting precursory events and using the rate of change in precursory phenomena such as minor tremors near the volcano. Hazard assess- ment studies have been carried our for only a small fraction of the earth's active volcanoes. Because of the costs, only a dozen volcanoes are well- monitored today, so that predicting eruptions is feasible for only these few. Loss of life and property due to volcanic activity can be significantly reduced through coordinated national and international efforts at volcanic hazard assessment, monitoring, and warning. Once volcanic risk areas are identified, zoning to restrict land use and development is the single most effective mitigation measure. Potential projects during the IDNHR include: ~ identification and global mapping of active and potentially active volcanoes;