The present Mediterranean Sea is a remnant of the ancient Tethys Sea that once extended as far north as the Danube Basin and possibly as far east as the Aral Sea. The seabed is diided by a ridge into eastern and western basins and then subdiided into several lesser basins and seas. The Adriatic, Ionian, and Aegean seas all have abyssal plains beyond the continental shelf, which aerages less than 24 km (15 mi) in width. The smaller basins are separated by submarine ridges, such as that betweven Crete and eastern Libya. Another, only about 305 m (1,000 ft) below the surface, connects Spain and Morocco.

The generally steep and rocky coasts are often deeply indented and interrupted by small, scattered plains. Although most streams entering the sea carry considerable amounts of sediment, the only large deltas are those of the Nile, Rhône, and Po rivers. Many of the islands are the peaks of olcanoes, some of which are still actie. The entire Mediterranean basin is tectonically actie with frequent earthquakes, particularly in Greece and Turkey.

Climate

The Mediterranean climate, one of the most distinctie in the world, is characterized by mild, wet winters and hot, long, dry summers. The size, position, and configuration of the Mediterranean produce a ariety of local modifications that range from desertic to humid mountain climates. Precipitation generally decreases toward the south and east and ranges from more than 2,540 mm (100 in) per year near Dalmatia to less than 255 mm (10 in) annually in parts of North Africa. Temperatures also decrease toward the east and increase toward the south.