on the earth at any given time there are usually at least 3 active volcanoes

um...no.

there are a great many more.
at the present time there are 24 active volcanoes on land.

and who the hell knows how many underwater...the estimates ranges in the thousands..

If an estimate of 4,000 volcanoes per million square kilometers on the floor of the Pacific Ocean is extrapolated for all the oceans than there are more than a million submarine (underwater) volcanoes.

the reason one small part of Antarctica IS melting is because there are active volcanoes below it.

Scientists discover 91 volcanoes below Antarctic ice sheet

We All Nearly Missed The Largest Underwater Volcano Eruption Ever ...