The Alps

The Alps serve as a natural barrier, trapping smog and haze in the valleys of northern Italy. In this image, taken on December 20, 2003, by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite, a veil of thin grey haze hangs around the base of the towering mountain range, filling in the canyons on the south side of the range. Further south, dense white fog covers the Plain of Lombardy. Smog is a frequent problem in northern Italy, where air is hemmed in by the Alps on the north and the Apennine mountains to the south.

The Alps are the highest and most extensive mountain range system that lies entirely in Europe, and stretch approximately 1,200 km across eight Alpine countries: France, Switzerland, Monaco, Italy, Liechtenstein, Austria, Germany, and Slovenia. The Alpine arch generally extends from Nice on the western Mediterranean to Trieste on the Adriatic and Vienna at the beginning of the Pannonian basin. The mountains were formed over tens of millions of years as the African and Eurasian tectonic plates collided. Extreme shortening caused by the event resulted in marine sedimentary rocks rising by thrusting and folding into high mountain peaks such as Mont Blanc and the Matterhorn. Mont Blanc spans the French–Italian border, and at 4,809 m is the highest mountain in the Alps. The Alpine region area contains 128 peaks higher than 4,000 m.

Credit: Jacques Descloitres, MODIS Rapid Response Team, NASA/GSFC