Irrigated land:
2,770,980 sq km (2003)
Natural hazards:
large areas subject to severe weather (tropical cyclones); natural disasters (earthquakes, landslides, tsunamis, volcanic eruptions)
volcanism: the world is home to more than 1,500 potentially active volcanoes, with over 500 of these having erupted in historical times; an estimated 500 million people live near these volcanoes; associated dangers include lava flows, lahars (mudflows), pyroclastic flows, ash clouds, ash fall, ballistic projectiles, gas emissions, landslides, earthquakes, and tsunamis; in the 1990s, the International Association of Volcanology and Chemistry of the Earth's Interior, created a list of 16 volcanoes worthy of special study because of their great potential for destruction: Avachinsky-Koryaksky (Russia), Colima (Mexico), Etna (Italy), Galeras (Colombia), Mauna Loa (United States), Merapi (Indonesia), Nyiragongo (Democratic Republic of the Congo), Rainier (United States), Sakurajima (Japan), Santa Maria (Guatemala), Santorini (Greece), Taal (Philippines), Teide (Spain), Ulawun (Papua New Guinea), Unzen (Japan), Vesuvius (Italy)
Environment - current issues:
large areas subject to overpopulation, industrial disasters, pollution (air, water, acid rain, toxic substances), loss of vegetation (overgrazing, deforestation, desertification), loss of wildlife, soil degradation, soil depletion, erosion; global warming becoming a greater concern
Geography - note:
the world is now thought to be about 4.55 billion years old, just about one-third of the 13.7-billion-year age estimated for the universe
People ::World