The main hub of volcanic activity is an area where eruptions are undetectable.
The mid-ocean ridge is an immense volcanic mountain chain that encircles the planet beneath the sea — the chain is more than 30,000 miles (48,000 kilometers) long and rises an average of 18,000 feet (5.5 kilometers) above the seafloor. This is the spot where Earth's plates spread apart as new crust bubbles up — causing much of the earth's volcanic eruptions.
There are more volcanoes here than on land. The spreading, however, leads to scrunching when these plates slam into the continents. The result: More volcanoes and earthquakes in places like California and Japan.
For land-based volcanoes, Indonesia is the hotbed for fiery craters since it is part of the roughly 25,000 mile stretch circling the basin of the Pacific Ocean known 'ring of fire' where most active volcanoes lie.