The geology of Armenia was shaped by geological upheaval pushed up the Earth's crust to form the Armenian Plateau 25 million years ago. This created the complex topography of Armenia. The Lesser Caucasus range extends through northern Armenia, runs southeast between Lake Sevan and Azerbaijan, then passes roughly along the Armenian-Azerbaijani border to Iran. Thus situated, the mountains make travel from north to south difficult.
Earthquakes
Geological turmoil continues in the form of devastating earthquakes. In December 1988, the second largest city in the republic, Gyumri, was heavily damaged by a massive quake that killed more than 25,000 people.
Terrain
About half of Armenia's area of approximately has an elevation of at least, and only 3% of the country lies below. The lowest points are in the valleys of the Araks River and the Debet River in the far north, which have elevations of, respectively. Elevations in the Lesser Caucasus vary between. To the southwest of the range is the Armenian Plateau, which slopes southwestward toward the Araks River on the Turkish border. The plateau is masked by intermediate mountain ranges and extinct volcanoes. The largest of these, Mount Aragats, high, is also the highest point in Armenia. Most of the population lives in the western and northwestern parts of the country, where the two major cities, Yerevan and Gyumri, are located. The valleys of the Debet River and Akstafa River as they pass through mountain areas form the chief routes into Armenia from the north. Lake Sevan is by far the largest lake at across at its widest point and long. It lies above sea level on the plateau. Armenia's terrain is most rugged in the extreme southeast, which is drained by the Bargushat River and most moderate in the Araks River valley to the extreme southwest. Most of Armenia is drained by the Araks or its tributary, the Hrazdan, which flow from Lake Sevan. The Araks forms most of Armenia's border with Turkey and Iran while the Zangezur Mountains form the border between Armenia's southern province of Syunik and Azerbaijan's adjacent Nakhchivan Autonomous Republic.
