Sandra Decker, age 15, of Pocatello, Ida., for her question:

WHAT EXACTLY ARE DALLES?

Dalles, pronounced "dalz," are deep gorges in which rivers flow rapidly over basaltic rocks or slabs. The name comes from the French "dalle," meaning "slab" or "tile."

The singular of dalles in English is dell, and in many parts of the country these gorges are called "dells" instead of "dalles."

French explorers gave the name dalles to scenic gorges of North American rivers, especially those located in the northern part of the United States. Notable dalles in the United States include the Wisconsin Dells of the Wisconsin River, near Wisconsin Delles, Wis.; the Saint Louis River Dalles near Duluth, Minn,; and the Saint Croix River Dalles between Wisconsin and Minnesota.

Near Wisconsin Dells, Wis., the river forms what many experts consider to be one of the most scenic spots in all of North America. Here the stream has cut its way through the sandstone rock to a depth of about 150 feet. It forms canyon walls cut in very unusual shapes.