Two mountain chains together run almost the entire length of Costa Rica. These are, in the north, the Cordillera Volcánica, famous, as the name implies, for its volcanic activity, and, in the south, the Cordillera de Talamanca. The Cordillera Volcánica may be separated into three ranges: from northwest to southeast, the Cordillera de Guanacaste, the Cordillera de Tilarán, and the Cordillera Central. The Cordillera de Talamanca is a massive granite batholith, quite different geologically from the volcanically active northern ranges. Costa Rica's highest point is Mount Chirripó, in the Talamanca system, at 12,533 feet. Two of the highest peaks in the Cordillera Volcánica, Irazú-11,260 feet and Poás-8,871 feet, have paved roads reaching to the rims of their active craters. These volcanoes overlook the densely populated upland basin called the Meseta Central, and they pose a serious natural hazard, as do earthquakes for most parts of the nation.