Here are some more volcanoes facts that you can read into depth.Why don't you guess how many volcanoes are in the U.S.? Have fun!

How many volcanoes have been identified in the world?
There are 1,500 active volcanoes around the world that has been discovered. A graph of the number of volcanoes of the world shows that it goes up just about as fast as the number of people on the earth does.

What country has the most volcanoes?
Indonesia has the most volcanoes. It is really a special place because there seem to be volcanoes all around, in all directions. Merapi (which means mountain of fire) erupted in January 1994 and killed a few hundred people.

How many volcanoes are there in the United States?
The lower 48 states in the U.S. have about 40 volcanoes that we think have had very recent activity, so they must be as active volcanoes. In Alaska, the number is more like 60. When we talk about whether a volcano is active or potentially a threat, it is important to look at the past ten years. Most of the important eruptions and disasters have happened at mountains that were not even recognized as being volcanoes, for example Pinatubo (Philippines, 1991), El Chichon (Mexico, 1982), Arenal (Costa Rica, 1968).

Sources:

http://www.learner.org/exhibits/volcanoes.html

www.learner.org/exhibits/meltrock.html

http:/teacher.scholastic.com/researchtools/articlearchives/volcanoes/general.htm

www.google.com

http://images.google.com/imgres?imgurl=http://www.pacificislandtravel.com/nature_

http://images.search.yahoo.com/search/images/view?back=http%3A%2F%2Fsearch.yah