Mark Connors, age 10, of Havertown, Pennsylvania, for his question:

What exactly is Eurasia?

Eurasia is a compound name that links together the continents of Europe and Asia. The continents of Africa and Antarctica, the Americas and Australia are geographically separated by natural boundaries of ocean. Europe and Asia are geographically linked in a single land mass. The north south line dividing them into two continents is an artificial one. Geographers prefer to view them as one and Eurasia is a sensible term for their purposes. There are other situations which also call for such a term. Al¬though the artificial boundary is clear enough on a map, it does not separate nature's populations of plants and animals. What's more, peoples living, on either side tend to mix and mingle. Referring to them as Eurasians makes it unnecessary to unscramble their mixed heritages and cultures.

Asia tops the world in size and population. Crowded Europe is the world's second smallest continent. Asia's more than 17 million square miles cover almost a third of the earth's land. Europe's four million square miles add only a fraction to the size of Eurasia. But the population of the merged continents is more than 75% of the world's total.