Pichincha is a n active composite or stratovolcano with a horseshoe - shaped crater (very similar to the newly formed crater by the explosion of Mount Saint Helens in 1980) with a diameter of 2 km and 600m deep. Its summit reaches 4787m and its exact geographical position is 0.171°S and 78.598°W , which locates it some 10 km west of Quito , Ecuador's capital . This city of 2 million people lies at the eastern foot of Mount Pichincha, however the crater is located away from the city with its opening pointing west towards the Pacific coast. Furthermore a range of hills protects the city from any eventual lava flows.