GEOLOGY. Western Greece, including two thirds of the mainland and nearly all the Pelo ponnesus, is composed of the long, parallel lime stone ridges of Tertiary formation, of the Di naric mountain system, the narrow troughs that separate them being schists and sandstone. This mountain region is a part of the Karst system which extends along the Adriatic; for, farther north, it exhibits the characteristic Karst phe nomena of caverns, sink-holes, and underground river channels, leaving much of the land dry and relatively barren. Some of the limestone has hardened into the purest marble. The same lime stone formation built up the Ionian Islands, once a part of the mainland. The rocks of Northeast Greece are of a different character, being the continuation of the crystalline rocks that built up the mountains of Thrace and Macedonia. Farther south, the eastern part of Central Greece, the island of Eubcea, and the northeastern part of the Peloponnesus are covered with mountain chains of Mesozoic limestone extending in curves from west to east. The crystalline rocks of the
Cyclades form the mountains, comparatively low, of these islands. Severe earthquakes often origi nate among the mountains. Greece is not rich in minerals, though the argentiferous lead-mines of Laurion, near the southeastern extremity of At tica, yield about 30,000 tons of lead a year. There is no coal except the lignite found in Eu bua. The lack of fuel prevents the large ex ploitation of the copper and iron fields, though important quantities of iron and zinc ores are obtained. Paros and Pentelleus yield fine mar ble, and emery is obtained in Naxos and other islands. Sulphur (about 600 tons a year) is mined in Melos and Santorini.