A volcano is a crack on the Earth’s crust through which molten material comes out.
When the eruptive activity of a volcano ceases, it is termed as ‘Extinct’. But, an extinct volcano can also come to life again.
This occurs probably due to the blockage of the chimney or pipe of the volcano within the Earth’s crust. The eruption of Mt. Vesuvius in A.D. 79 proves that, an extinct volcano can become active again.
Mainly, volcanoes are found in the Pacific belt of Fire, Atlantic Ocean, Mediterranean sea, Great Rift Valley region near the African lakes.
Below Extinct Volcanoes info from Wikipedia (Read More):-
Extinct volcanoes are those that scientists consider unlikely to erupt again, because the volcano no longer has a lava supply. Examples of extinct volcanoes are many volcanoes on the Hawaiian Islands in the U.S. (extinct because the Hawaii hotspot is centered near the Big Island), and Paricutin, which is monogenetic. Otherwise, whether a volcano is truly extinct is often difficult to determine. Since "supervolcano" calderas can have eruptive lifespans sometimes measured in millions of years, a caldera that has not produced an eruption in tens of thousands of years is likely to be considered dormant instead of extinct. For example, the Yellowstone Caldera in Yellowstone National Park is at least 2 million years old and hasn't erupted violently for approximately 640,000 years, although there has been some minor activity relatively recently, with hydrothermal eruptions less than 10,000 years ago and lava flows about 70,000 years ago. For this reason, scientists do not consider the Yellowstone Caldera extinct. In fact, because the caldera has frequent earthquakes, a very active geothermal system (i.e. the entirety of the geothermal activity found in Yellowstone National Park), and rapid rates of ground uplift, many scientists consider it to be an active volcano.
http://en.wikipedia.org/wiki/Extinct_volcano#Extinct
