Monday, August 17, 2009

Geologic Hazards

The geologic processes that formed the spectacular landscapes of many national parks remain active today, and can be hazardous to park visitors, staff, infrastructure, and neighbors. Potentially hazardous processes include volcanic eruptions and other geothermal related features, earthquakes, landslides and other slope failures, mudflows, sinkhole collapses, snow avalanches, flooding, glacial surges and outburstfloods, tsunamis, and shoreline movements.

What are Geologic Hazards?
Geohazards are any geological or hydrological process that poses a threat to people and/or their property.

• Masses of rock or ice that fall or slide suddenly under the force of gravity.
• A sudden ground motion or vibration of the Earth. Produced by a rapid release of stored-up energy along an active fault.
• The point on the Earth’s surface located directly above the focus of an earthquake
• Occurs when solid, liquid or gaseous volcanic materials are ejected into the Earth’s atmosphere or surface by volcanic activity. Eruptions may occur as quiet lava flows or violent explosive events.
• Magma that reaches the Earth’s surface through a volcanic eruption. When cooled and solidified, forms extrusive (volcanic) igneous rock.
• Molten rock. Magma may be completely liquid or a mixture of liquid rock, dissolved gases and crystals. Molten rock that flows out onto the Earth’s surface is called lava.
Mass wasting
• Movement of rock and soil down slope under the influence of gravity.
• The solid structure created when lava, gases, and hot particles escape to the Earth's surface through vents. Volcanoes are usually conical. A volcano is "active" when it is erupting or has erupted recently. Volcanoes that have not erupted recently but are considered likely to erupt in the future are said to be "dormant." A volcano that has not erupted for a long time and is not expected to erupt in the future is "extinct."
Tsunami (plural tsunami)
• A vast sea wave caused by the sudden dropping or rising of a section of the sea floor following an earth- quake. Tsunami may be as much as 30 meters high and 200 kilometers long, may move as fast as 250 kilometers an hour, and may continue to occur for as long as a few days.


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