What is a natural hazard?
A natural hazard is a naturally occuring physical event which poses a threat and negatively impacts people and the environment. Examples of natural hazards are: earthquakes, tsunamis, wildfires, floods, volcanic eruptions etc.
Earthquakes and their Occurence
What is an Earthquake?
An earthquake is a sudden rapid vibration along the earth’s crust due to individual tremors, sometimes causing great destruction to the earth’s lithosphere and its inhabitants. Earthquakes occur both on land and sea.They may occur at areas where plates collide (subduction zones/ convergent plate margins) ; where plates slide past eachother along fault lines (transform plate margins) or due to volcanic eruption. Earthquakes may be of three different categories:
* Tectonic – movement in the earth’s crust due to sudden movement along fault lines. * Plutonic - occurs deep within the subduction zone of colliding plates. * Volcanic – earthquakes accompanied by molten lava and gases. Earthquakes may be of different intensities which determines how much damage it causes to life and property. The intensity of an earthquake is recorded by seismographs which are measured by the Mercalli Scale. The Richter Scale measures the magnitude of the earthquake. How do Earthquakes Occur?
At a Zone of Convergence:
At a zone of convergence, tectonic plates move towards each other causing collision. A denser oceanic crust sinks beneath a less dense continental crust to form a subduction zone. Where plates collide at subduction zones plate edges are destroyed. This collision is associated with seismic/earthquake activity.
At Transform Plate Margins:
At transform plate margins tectonic plates slide parallel to each other, but in opposite directions causing a build up of friction. This friction causes plates to jerk and snap triggering an earthquake.
Earthquakes produced by stress changes in solid rock due to the injection...
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