Why do Earthquakes most often occur at constructive and destructive plate boundaries? PLEASE HELP! x

3 Answers

  • ProTon
    Lv 5
    1 decade ago
    Favorite Answer

    Most of the earthquakes are confined to narrow belts and these belts define the boundaries of the plates. The interiors of the plates themselves are largely free of large earthquakes, that is, they are aseismic.

    Plate tectonics confirms that there are four types of seismic zones. The first follows the line of midocean ridges. Activity is low, and it occurs at very shallow depths. The point is that the lithosphere is very thin and weak at these boundaries, so the strain cannot build up enough to cause large earthquakes. Associated with this type of seismicity is the volcanic activity along the axis of the ridges (for example, Iceland, Azores, Tristan da Cunha).

    The second type of earthquake associated with plate tectonics is the shallow-focus event unaccompanied by volcanic activity. The San Andreas fault is a good example of this, so is the Anatolian fault in Northern Turkey. In these faults, two mature plates are scraping by one another. The friction between the plates can be so great that very large strains can build up before they are periodically relieved by large earthquakes. Nevertheless, activity does not always occur along the entire length of the fault during any one earthquake. For instance, the 1906 San Francisco event was caused by breakage only along the northern end of the San Andreas fault.

    The third type of earthquake is related to the collision of oceanic and continental plates. One plate is thrust or subducted under the other plate so that a deep ocean trench is produced. In the Philippines, ocean trenches are associated with curved volcanic island arcs on the landward plate, for example the Java trench. Along the Peru - Chile trench, the Nazca plate is being subducted under the South American plate which responds by crumpling to form the Andes. This type of earthquake can be shallow, intermediate, or deep, according to its location on the downgoing lithospheric slab. Such inclined planes of earthquakes are know as Benioff zones.

    The fourth type of seismic zone occurs along the boundaries of continental plates. Typical of this is the broad swath of seismicity from Burma to the Mediterranean, crossing the Himalayas, Iran, Turkey, to Gilbraltar. Within this zone, shallow earthquakes are associated with high mountain ranges where intense compression is taking place. Intermediate- and deep-focus earthquakes also occur and are known in the Himalayas and in the Caucasus. The interiors of continental plates are very complex, much more so than island arcs. For instance, we do not yet know the full relationship of the Alps or the East African rift system to the broad picture of plate

  • 1 decade ago

    Earthquakes can occur anywhere. However, they are unevenly distributed over the earth, with the majority occurring at the boundaries of the major crustal plates. These plate boundaries are of three types destructive, where the plates collide; constructive, where the plates move apart; and conservative plate boundaries, like the San Andreas Fault, where the plates slide past each other. Earthquakes also occur, less frequently, within the plates and far from the plate boundaries, as in eastern USA, Australia and the United Kingdom.

  • Anonymous
    4 years ago

    I think it's the frequency with which they are happening, along with the death-toll, that is worrying. Haiti on January 14 (scale - 7); Chile on 27 February (scale - 6.2); Turkey on 8 March (scale 6.2) and Sumatra on 6 April (scale 7.8). Regardless of whether this is perceived as nothing abnormal, the effect on human lives has been devastating. It will only take an earthquake in a densely populated area such as the U.S.A. for some people to wake up. One of the many signs of the end of the age is "great earthquakes, famines and pestilences in various places, and fearful events and great signs from heaven" (Luke 21:11). Needless to say, there have been great earthquakes, famines and pestilences for the last 2,000 years. What demands our attention, from God's point of view, is that despite all the trials and tribulations that will culminate in the end of the age, those who have placed their faith in Christ Jesus as Lord and Saviour, and who stand firm, need not fear. "There will be signs in the sun, moon and stars. On the earth, nations will be in anguish and perplexity at the roaring and tossing of the sea. Men will faint from terror, apprehensive of what is coming on the world, for the heavenly bodies will be shaken. At that time they will see the Son of Man (Jesus Christ) coming in a cloud with power and great glory. When these things begin to take place, stand up and lift up your heads, because your redemption is drawing near" (Luke 21:25-28). I suspect things are going to get an awful lot worse before they start to get better.

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