Juli Walker, age 13, of Bessemer, Ala., for her question:

HOW WIDE IS THE STRAIT OF GIBRALTAR?

The Strait of Gibraltar is a narrow passage connecting the Mediterranean Sea on the east with the Atlantic Ocean on the west and separating North Africa from the Rock of Gibraltar on the southernmost point of the Iberian peninsula. The strait is about 40 miles long and varies in width from about nine to 24 miles.

A channel about five miles wide, traversing the center of the strait, has a depth of about 1,000 feet.

A continuous central current enters from the Atlantic Ocean, and tidal currents ebb and flow along the European and African shores.

An undercurrent flowing westerly carries off the surplus waters of the Mediterranean.

The eastern end of the Strait of Gibraltar is flanked by the Pillars of Hercules. This is a name given by the ancient Greeks to two peaked rocks that flank the entrance. They seem to have been first visited by the Phoenicians about 1100 B.C. Ancient Calpe, the north pillar, is the modern Rock of Gibraltar, and ancient Abila, situated at Ceuta on the African coast, is now called Jebel Musa.