The crust and the top of the mantle make up a thin skin on the surface of our planet. But this skin is not all in one piece — it is made up of many pieces like a puzzle covering the surface of the earth. Not only that, but these puzzle pieces keep slowly moving around, sliding past one another and bumping into each other. We call these puzzle pieces tectonic plates , and the edges of the plates are called the plate boundaries.
The plate boundaries are made up of many faults, and most of the earthquakes around the world occur on these faults. Since the edges of the plates are rough, they get stuck while the rest of the plate keeps moving. Finally, when the plate has moved far enough, the edges unstick on one of the faults and there is an earthquake. The tectonic plates divide the Earth's crust into distinct "plates" that are always slowly moving.
Earthquakes are concentrated along these plate boundaries. While the edges of faults are stuck together, and the rest of the block is moving, the energy that would normally cause the blocks to slide past one another is being stored up.
When the force of the moving blocks finally overcomes the friction of the jagged edges of the fault and it unsticks, all that stored up energy is released. The energy radiates outward from the fault in all directions in the form of seismic waves like ripples on a pond. The cartoon sketch of the seismograph shows how the insrument shakes with the earth below it, but the recording device remains stationary instead of the other way around.
Earthquakes are recorded by instruments called seismographs. The recording they make is called a seismogram. The seismograph has a base that sets firmly in the ground, and a heavy weight that hangs free.
When an earthquake causes the ground to shake, the base of the seismograph shakes too, but the hanging weight does not. Instead the spring or string that it is hanging from absorbs all the movement.
Collapse quakes can be triggered by such phenomena as cave-ins, mostly in karst areas or close to mining facilities, as a result of subsidence. Causes of Earthquakes in General. Causes of Earthquakes in Switzerland. Causes of Earthquakes in Europe. In the early s, the emergence of the theory of plate tectonics started a revolution in the earth sciences.
Since then, scientists have verified and refined this theory, and now have a much better understanding of how our planet has been shaped by plate-tectonic processes.
We now know that, directly or indirectly, plate tectonics Where were the land areas and oceans of the North American Continent one million years ago, compared to our present geography? Was North America always about the same size and shape as it is today? To answer these questions, we must construct maps of the lands and sea that existed during the past ages. This process of reconstructing ancient A new report issued by the American Red Cross and the U.
Geological Survey documents the Chilean response and recovery efforts following the Feb. According to the U. Geological Survey USGS , was the deadliest year for earthquakes since the Renaissance Age, making it the second most fatal in recorded history, with more than , deaths reported from the magnitude 9.
This database contains information on faults and associated folds in the United States that demonstrate geological evidence of coseismic surface deformation in large earthquakes during the Quaternary the past 1. Skip to main content. Search Search.
Natural Hazards. Apply Filter. What is the difference between aftershocks and swarms? Aftershocks are a sequence of earthquakes that happen after a larger mainshock on a fault. Aftershocks become less frequent with time, although they can continue for days, weeks, months, or even Do earthquakes occur in Antarctica?
Earthquakes do occur in Antarctica, but not very often. There have been some big earthquakes--including one magnitude 8 --in the Balleny Islands between Antarctica and New Zealand.
The boundary between the Scotia Plate and the Antarctic Plate just grazes the north tip of the Antarctic Peninsula look "northwest" from the Pole toward South Where can I find earthquake educational materials?
Start with our Earthquake Hazards Education site. Can we cause earthquakes? The waves of energy spread out from the point where the earthquake started — the focus.
More damage occurs near the focus. If you've found the resources on this page useful please consider making a secure donation via PayPal to support the development of the site. The site is self-funded and your support is really appreciated.
If you've found the resources on this site useful please consider making a secure donation via PayPal to support the development of the site. Why do earthquakes happen? Cross section of an earthquake.
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