Creation of Volcanoes [Comment]
Most active volcanoes ultimately derive their energy from processes associated with the theory of plate tectonics. Volcanoes tend to coincide with major plate boundaries, though some, like the Hawaiian Islands, formed over hot spots in the earth's surface far from plate boundaries.
At subduction zones, where one plate moves beneath ... [More
] Debris flows and mudflows [Comment]
Debris flows (also referred to as mudslides, mudflows, or debris avalanches) are debris laden flows of water, often the consistency of wet concrete, that move surprisingly quickly down steep slopes. They move so rapidly (to speeds of 35 miles per hour or more) that they are generally unexpected, destroying property and taking lives. ... [More
] Detecting, locating, and measuring earthquakes [Comment]
Several thousand stations monitor earthquakes all over the world. Each station contains an instrument, called a seismograph, used to detect arrival times and record seismic waves. The seismograph consists of a seismometer (the detector) and a recording device. The seismometer electronically amplifies wave motion.
The graph on which ... [More
] Earthquake damages (secondary effects) [Comment]
Effects of an earthquake can be classified as primary or secondary. Primary effects are permanent features produced by the earthquake. Examples include fault scarps, surface ruptures, and offsets of natural or human-constructed objects. An example you have already seen is the creek offset produced by movement along the San Andreas ... [More
] Earthquake processes [Comment]
Rupturing rocks release huge amounts of energy. The sudden release of energy is what is felt in an earthquake. Earthquake energy is in the form of seismic waves. The seismic waves radiate out from a central point, called the focus or hypocenter, like ripples moving outward from a pebble tossed into a lake. The location directly above the ... [More
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