Becky Wright, age 10, of Tuscon, Ariz., for Her question:

What does lava mean? '

The word lava comes from an older word meaning to wash. The Italians of Naples called a teeming downpour a_lava ‑ it washed their streets. How then could lava mean certain rocks? It means liquid or flowing rock. It also means rocks that were once fluid and have since cooled.

It takes terrific heat to melt rocks to the runny stage. This can happen in the seething fury of a volcano. All kinds of rocks and minerals are heated together into this molten stage. Sometimes the lava flows out in a long river, sometimes it covers the ground in sheets.

Sooner or later the hot, liquid lava cools. The different kinds of solid lava depend upon the different minerals melted in the brew, The solid rock also depends upon how fast or how slowly it cooled. Fast cooling‑lava may form the black, glass rock q.lled obsidian. Lava seething with bubbly gases forms pumice stone.