No one knows for sure how many volcanoes there are in the world. In some cases there are large fields of connected hot spots that make the task of counting difficult. Scientists think that over the entire history of the Earth there have been millions of volcanoes. For the past 10,000 years it is believed that there have been 10,000 separate volcanoes and volcanic fields. What the scientists can count is the number of eruptions that occur each year. Over modern history this number has been fairly consistent at between 50 and 70. However, last year broke the record for the number of volcanic eruption. By the beginning of December there had already been 83 eruptions, plus there were a few more after that. The previous record was set in 2010 at 82. More than 20 volcanoes were still active at the end of 2013. Plus these numbers only include the eruptions that occur on the surface of the Earth. They do not include the number of eruptions that occur on the ocean floor, which seem also to be increasing.
When you look at the data, it is clear that the number of eruptions per year has been going up at a steady rate, especially since 1990. By combining data from various web pages, I created the following chart. On the chart for each decade the number of eruptions were divided by 10 to give the average number of eruptions per decade year.
The next four photos show Mount St. Helens.
Some more photos taken by NASA of active volcanoes are below.