Abstract: The regions where most of tsunamis originate are Japan, Peru, Chile, the New Guinea and the Solomon Islands. The emergence of tsunamis may be caused by the following factors: 1) earthquakes; 2) volcanic eruptions; 3) rockfalls; 4) landslides; 5) submarine landslides; 6) submarine explosions; 7) meteorological reasons. Damage is caused by: 1) flood due to quick rise of the sea level; 2) dynamic load on constructions; 3) hits by floating wreckages; 4) soil wash-out at foundations by the fast water stream; 5) fluctuations of water level (leading first of all to the damage of vessels moored: 6) dynamic impact of the air wave in front of a tsunami. Tsunamis cause considerable mortality and influence a number of objects and types of human activity: 1) residential and industrial buildings; 2) water transport; 3) plant growing; 4) forestry, etc.
Abstract: Altogether about 2500 volcanoes exist on Earth, and during the last 3500 years, 959 of them erupted. About 360 mln. people live in dangerous proximity to actve volcanoes. On average about 50 volcanoes erupt each year. Catastrophic events may result from six volcanic processes, viz. 1) ejection of rock debris; 2) lava flows; 3) ejection of volcanic gases; 4) burning volcanic clouds; 5) volcanic landslides; 6) lahars. Each eruption manifests itself in several volcanic processes, but only one or two of them may prevail. First of all volcanic eruptions are dangerous for the following human activities: 1) transportation; 2) agriculture; 3) communication & electricity transmission lines; 4) residential building. Average annual mortality from them is about 800 persons and economic loss amount to $800-900 million.