Essay On Earthquakes And Earthquakes

952 Words4 Pages
Where are earthquakes and volcanoes found? Volcanoes and earthquakes have been known to man for thousands of years, but until fairly recently their distribution on the globe was thought of as totally haphazard with each event an isolated phenomenon. Yet, if the positioning of the world’s volcanoes is considered, it can be seen that most volcanoes are situated within several hundred kilometres of the sea, and moreover, that the regions of volcanic activity are concentrated into several girdles or bands circling the Earth. Most notable amongst these are the so-called “Ring of Fire” surrounding the Pacific Ocean (see figure 1), and the more tenuous and disjointed line running down the centre of the Atlantic Ocean. Throughout geological history, igneous activity has been restricted in the same way, as studies of ancient igneous rocks show. Similarly, earthquakes do not occur randomly over the whole surface of the Earth. Their epicentres also fall into welldefined bands girdling the planet, and in fact, seismic and volcanic activity are well-correlated – so that bands of concentration for each coincide (Figure 1). Figure 1. Map of the world showing the location of tectonic plate boundaries, volcanoes, hot spots, and earthquake zones. Note how the majority of seismic and volcanic events are concentrated on plate boundaries. Tectonic plates and their boundaries These concentrations of geological activity actually define the boundaries of huge, rigid fragments of the

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