Cotopaxi is a glacierized active volcano in the tropics, Ecuador's highest active volcano at 5897 meters (19,347 feet). It is a stratovolcano with an almost perfectly symmetrical cone, rising from a highland plain of 3800m. The side of the cone has deep valleys scoured by lahars. The summit crater is 600m x 800m in diameter and several hundred meters deep. Despite Ecuadorians claiming it to be the highest active volcano in the world, it is untrue, that record belonging to Volcan Ojos del Salado, in Chile, at 6893 meters (then to Volcan Llullaillaco at 6739 meters, etc, etc).

Cotopaxi has a well recorded history of explosive eruptions (57 since 1534) with lava and pyroclastic flows, which often devastated parts of nearby valleys. During a battle between Incas and Spaniards in 1534 the volcano erupted and put an end to the fighting as both fled from the battle field (the locals took it as an ominous sign; in light of Spanish conquest they were right). Eruptions in 1744 and 1768 destroyed the colonial town of Latacunga and in 1877 a huge eruption produced lahars which reached the Pacific ocean (via rivers) and western Amazon basin, more than 100 km away.

The main danger of a huge eruption of Cotopaxi would be the ensuing flow of mud and ice from its glacier (lahars). Computer models calculated lahars of eight meters coming down by way of River Pita to the valley of Los Chillos, nowadays a main suburban area of Quito with a population of more than 100 000 people living there. Another major city in danger would be Latacunga to the southwest of Cotopaxi and all the small farming villages skirting the mountain.

Many experts think that another eruptive stage might be coming very soon. In the last few years fumarolic activities and sulfuric emissions increased and ice around the inside rim melted away giving a clear view to the bottom. Also, fumaroles can be seen steaming out through the rock face of Yanasacha, which is located some two hundred meters below the summit.