Total number of volcanoes with reported eruptions per year (thin upper black line) and 10-year running mean of same data (thick upper red line). Graph showing the number of volcanoes reported to have been active each year since 1800 CE. Their constancy over the past two centuries is a better indicator of the global frequency of eruptions than the improved reporting of smaller eruptions.įigure 1. The best evidence that these trends are apparent rather than real comes from the record of large eruptions, whose effects are far reaching and less likely to escape documentation even in remote areas. The apparent increase in activity reflects increases in populations living near volcanoes to observe eruptions and improvements in communication technologies to report those eruptions. However, even in the last two centuries any real trends are overshadowed by reporting factors such as historical events, technological changes, and exploration influences. The last 200 years of the volcanological record (figure 1), with humans distributed over most of the globe and relatively efficient communications, would seem to be the well-suited to search for episodic trends. Readers are strongly cautioned against mistaking the record for the reality. There is great value in knowing the recent volcanological record, but its limitations are not always apparent. Please do not reproduce the figures below without all of the accompanying analysis and proper citation (links are preferred). (2010) data is through 2009, but more recent data is available. The following figures and discussion are modified from an introductory section in Siebert et al. Data about eruptions has been compiled by the Smithsonian since 1968 in order to provide context for global volcanism. The Global Volcanism Program does not see any evidence that volcanic activity is actually increasing.
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