The most distinctive of the surrounding mountains is the Nevado de Toluca (4,690 masl) to the southwest. The Nevado is the fourth highest mountain in Mexico at 4,600 masl, formed by successive eruptions with deposited layers of igneous materials . Its peak has snow most of the year and is surrounded by temperate forests. The mountain has important effects on the climate and hydrology of the Toluca Valley The piedmont is characterized by hills covered by broadleaf forests. On the upper slopes there are conifers. The highest elevations have alpine grasslands, known as Zacatonal.