Popcatepetl

As you are traveling across the United States, you can see many landmarks created by volcanoes centuries ago. With the naked eyes, you can identify cone shaped volcanoes, but you can miss other volcanic landscapes. Some volcanoes build mountains, but only during their actives lives when volcanoes stop erupting they begin to wear down, or erode. Only portions of the original mountain remain. Other volcanoes don't build mountains at all instead; their lava floods a landscape, drowning forests, hills and valleys. Sometimes during an eruption the top of a volcanic cone collapses and a crater, or caldera, forms. Craters measure from hundreds of miles across the volcanoes mountain.

Popocatйpetl is a volcano with forested slopes and a snow-capped cone and large crater. It is the second known highest mountain in the United States and located outside of Puebla, Mexico, at a distance of 17,925 feet (5,465 m) high. The name Popocatйpetl is Aztec for Smoking Mountain, and is often conveniently shortened to Popo. Popo and its neighboring volcano Iztaccihuatl 17,342 ft, have dominate the sky southeast of downtown Mexico City, and 45 km (30 miles) southwest of the city of Puebla. Both volcanoes are located less than fifty miles from each city, and are separated from each other by a ten-mile ridge.

Popocatйpetl, one of the world's most active volcanoes, located in central Mexico is known as an andesitic volcano, which means it's forming where two tectonic plates rub up against each other, grinding down the material with enough friction and heat to melt rock and create magma. There two major types of Volcanoes, one is Andes tic and the other is basaltic. These two typical volcanoes begin life when a mass of low-density magma forces its way to the surface. When the density of the rising magma is the same as that of the surrounding rock, it gathers in a magma chamber. Any rise in pressure in the chamber may now push the magma upwards through cracks in the overlying rock. As the magma traveling up a crack approaches the surface, the pressure from the overlying rocks reduces; gases are released from the magma and expand so suddenly that an explosion rips open a funnel shaped vent to the surface. The lava that blasts out of the vent then cools, to form cinders, ash and dust - all referred to as "Tephra". A ring of Tephra collects around the vent and, as the eruption subsides, this blocks up the diatreme.

History show that the last major eruption of Popocatйpetl was in 1947, although on December 21, 1994, it awakened from dormancy, spewing gas and ash, which was carried by the wind as far as Puebla, 25 miles east. Surrounding towns were evacuated, and scientists have since been closely monitoring Popo for signs of a possible eruption. The other monitoring parameters remain without important changes. The recent activity is within the expected scenarios and there is no evidence of a major risk in the following days. The monitoring system continues permanently. From high to low probability, the expected activity scenarios in the next probably will be small exhalations, some with light ash emissions, occasionally mild incandescence during nights and sporadic low level explosions with low probabilities of incandescent fragment at short distance to the crater.

In conclusion, volcanoes are like sleeping giants. After years - even centuries - of resting, they