Keith Green, age 11, of Marshall, North Carolina, for his question:

Which is the highest volcano in the world?

This sounds like a simple enough question to answer with the help of an atlas and a couple of geography books. But there are at least two snags to the problem. Mountains and their hot tempered volcano cousins are measured from sea level. The massive volcanos that form the islands of Hawaii stand on the solid sea bed miles be¬low the water. The measurement of these ponsters should include both their under water and their above water heights. But we will disqualify them and select today's volcano from those that stand fair and square on the dry land.

The next problem concerns the state of a volcano. It may be in the active class, eager to erupt at any time. It may be in the dormant class, with few if any recorded eruptions. Or it may be an old fellow in the extinct class, never able to stir again. The world's largest volcano is extinct. It is massive, snow capped Mount Aconcagua in Argentine. Its height is 22,834 feet above sea level, which makes it also the highest mountain in the Western Hemisphere. The tallest active volcano is in nearby Chile and is also in the lofty Andes. It is Mount Guillatire,standing 19,882 feet high. Africa's Kilimanjaro is 19,340 feet high and rates as the world's tallest dormant volcano.