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Friction produces stress and temperature increases; the subducted rock melts and expands, causing additional stress and upward movement of the magma.
The magma reaches the surface, erupting to form volcanoes, and the crustal rocks respond to the stresses by breaking and moving.
High density of population and infrastructure increases the risk, making hazard mitigation even more important.
Geologic events are distinctive for their extremely rapid onset.
In the successive stages of development planning, the hazard mitigation work becomes more detailed and specialized. Earthquake Hazard Prediction, Assessment, and Mitigation 3. Earthquake Hazards and the Development Planning Process An earthquake is caused by the sudden release of slowly accumulating strain energy along a fault within the earth's crust.
Thus, the chapter concentrates on the early phases of development studies, in which the assessment of geologic hazards and the identification of mitigation measures fit comfortably within a planning study. Areas of surface or underground fracturing that can experience earthquakes are known as earthquake fault zones.
However, not all earthquake faults have been identified.Unlike a flood or hurricane, whose impact at a site can be forecast hours or days in advance, earthquakes give virtually no warning.Volcanoes often show signs of a general increase in activity but give little or no warning of the actual eruption.Latin America suffers its share of this destructive force: during the period 1985-1987, earthquakes in Ecuador, Mexico, and El Salvador and a volcanic eruption in Colombia killed more than 36,000 people.The Nazca Plate, sliding slowly eastward on the earth's mantle, slips under the South American Plate along the Peru-Chile Trench.