The surface of the Earth is approximately 70.9% water and 29.1% land. The former portion is divided into large bodies termed oceans. The World Factbook recognizes and describes five oceans, which are in decreasing order of size: the Pacific Ocean, Atlantic Ocean, Indian Ocean, Southern Ocean, and Arctic Ocean. Because of their immense size, the Pacific and Atlantic Oceans are generally divided at the equator into the North and South Pacific Oceans and the North and South Atlantic Oceans, thus creating seven major water bodies - the so-called "Seven Seas."
Some 97.5% of the Earth's water is saltwater. Of the 2.5% that is fresh, about two-thirds is frozen mostly locked up in the Antarctic ice sheets and mountain glaciers worldwide. If all the surface ice on earth fully melted, the sea level would rise about 70 m.
Earth's land portion is generally divided into several, large, discrete landmasses termed continents. Depending on the convention used, the number of continents can vary from five to seven. The most common classification recognizes seven, which are (from largest to smallest): Asia, Africa, North America, South America, Antarctica, Europe, and Australia. Asia and Europe are sometimes lumped together into a Eurasian continent resulting in six continents. Alternatively, North and South America are sometimes grouped as simply the Americas, resulting in a continent total of six (or five, if the Eurasia designation is used).
North America is commonly understood to include the island of Greenland, the isles of the Caribbean, and to extend south all the way to the Isthmus of Panama. The easternmost extent of Europe is generally defined as being the Ural Mountains and the Ural River; on the southeast the Caspian Sea; and on the south the Caucasus Mountains, the Black Sea, and the Mediterranean. Portions of five countries - Azerbaijan, Georgia, Kazakhstan, Russia, and Turkey - fall within both Europe and Asia, but in every instance the larger section is in Asia. These countries are considered part of both continents. Armenia and Cyprus, which lie completely in Western Asia, are geopolitically European countries.
Asia usually incorporates all the islands of the Philippines, Malaysia, and Indonesia. The islands of the Pacific are often lumped with Australia into a "land mass" termed Oceania or Australasia. Africa's northeast extremity is frequently delimited at the Isthmus of Suez, but for geopolitical purposes, the Egyptian Sinai Peninsula is often included as part of Africa.
Although the above groupings are the most common, different continental dispositions are recognized or taught in certain parts of the world, with some arrangements more heavily based on cultural spheres rather than physical geographic considerations.
Based on the seven-continent model, and grouping islands with adjacent continents, Africa has the most countries with 54. Europe contains 49 countries and Asia 48, but these two continents share five countries: Azerbaijan, Georgia, Kazakhstan, Russia, and Turkey. North America consists of 23 sovereign states, Oceania has 14, and South America 12.
countries by continent: Africa (54): Algeria, Angola, Benin, Botswana, Burkina Faso, Burundi, Cabo Verde, Cameroon, Central African Republic, Chad, Comoros, Democratic Republic of the Congo, Republic of the Congo, Cote d'Ivoire, Djibouti, Egypt, Equatorial Guinea, Eritrea, Eswatini, Ethiopia, Gabon, The Gambia, Ghana, Guinea, Guinea-Bissau, Kenya, Lesotho, Liberia, Libya, Madagascar, Malawi, Mali, Mauritania, Mauritius, Morocco, Mozambique, Namibia, Niger, Nigeria, Rwanda, Sao Tome and Principe, Senegal, Seychelles, Sierra Leone, Somalia, South Africa, South Sudan, Sudan, Tanzania, Togo, Tunisia, Uganda, Zambia, Zimbabwe;
Europe (49): Albania, Andorra, Austria, Azerbaijan*, Belarus, Belgium, Bosnia and Herzegovina, Bulgaria, Croatia, Czech Republic, Denmark, Estonia, Finland, France, Georgia*, Germany, Greece, Holy See (Vatican City), Hungary, Iceland, Ireland, Italy, Kazakhstan*, Kosovo, Latvia, Liechtenstein, Lithuania, Luxembourg, Malta, Moldova, Monaco, Montenegro, Netherlands, North Macedonia, Norway, Poland, Portugal, Romania, Russia*, San Marino, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey*, Ukraine, United Kingdom (* indicates part of the country is also in Asia);
Asia (48): Afghanistan, Armenia, Azerbaijan*, Bahrain, Bangladesh, Bhutan, Brunei, Burma, Cambodia, China, Cyprus, Georgia*, India, Indonesia, Iran, Iraq, Israel, Japan, Jordan, Kazakhstan*, North Korea, South Korea, Kuwait, Kyrgyzstan, Laos, Lebanon, Malaysia, Maldives, Mongolia, Nepal, Oman, Pakistan, Philippines, Qatar, Russia*, Saudi Arabia, Singapore, Sri Lanka, Syria, Tajikistan, Thailand, Timor-Leste, Turkey*, Turkmenistan, United Arab Emirates, Uzbekistan, Vietnam, Yemen (* indicates part of the country is also in Europe);
North America (23): Antigua and Barbuda, The Bahamas, Barbados, Belize, Canada, Costa Rica, Cuba, Dominica, Dominican Republic, El Salvador, Grenada, Guatemala, Haiti, Honduras, Jamaica, Mexico, Nicaragua, Panama, Saint Kitts and Nevis, Saint Lucia, Saint Vincent and the Grenadines, Trinidad and Tobago, United States;
Oceania (14): Australia, Fiji, Kiribati, Marshall Islands, Federated States of Micronesia, Nauru, New Zealand, Palau, Papua New Guinea, Samoa, Solomon Islands, Tonga, Tuvalu, Vanuatu;
South America (12): Argentina, Bolivia, Brazil, Chile, Colombia, Ecuador, Guyana, Paraguay, Peru, Suriname, Uruguay, Venezuela
the world from space: Earth is the only planet in the Solar System to have water in its three states of matter: liquid (oceans, lakes, and rivers), solid (ice), and gas (water vapor in clouds); from a distance, Earth would be the brightest of the eight planets in the Solar System; this luminous effect would be because of the sunlight reflected by the planet's water
Map references:
Physical Map of the World
Area:
total: 510.072 million sq km
[see also: Area - total country ranks ]
land: 148.94 million sq km
[see also: Area - land country ranks ]
water: 361.132 million sq km
note: 70.9% of the world's surface is water, 29.1% is land
Area - comparative:
land area about 16 times the size of the US
Africa-US area comparison map
Antarctica-US area comparison map
Asia-US area comparison map
Australia-US area comparison map
Europe-US area comparison map
North America-US area comparison map
South America-US area comparison map
Area - rankings:
top fifteen World Factbook entities ranked by size: Pacific Ocean 155,557,000 sq km; Atlantic Ocean 76,762,000 sq km; Indian Ocean 68,556,000 sq km; Southern Ocean 20,327,000 sq km; Russia 17,098,242 sq km; Antarctica 14,200,000 sq km; Arctic Ocean 14,056,000 sq km; Canada 9,984,670 sq km; United States 9,826,675 sq km; China 9,596,960 sq km; Brazil 8,515,770 sq km; Australia 7,741,220 sq km; European Union 4,324,782 sq km; India 3,287,263 sq km; Argentina 2,780,400 sq km
top ten largest water bodies: Pacific Ocean 155,557,000 sq km; Atlantic Ocean 76,762,000 sq km; Indian Ocean 68,556,000 sq km; Southern Ocean 20,327,000 sq km; Arctic Ocean 14,056,000 sq km; Coral Sea 4,184,100 sq km; South China Sea 3,595,900 sq km; Caribbean Sea 2,834,000 sq km; Bering Sea 2,520,000 sq km; Mediterranean Sea 2,469,000 sq km
top ten largest landmasses: Asia 44,568,500 sq km; Africa 30,065,000 sq km; North America 24,473,000 sq km; South America 17,819,000 sq km; Antarctica 14,200,000 sq km; Europe 9,948,000 sq km; Australia 7,741,220 sq km; Greenland 2,166,086 sq km; New Guinea 785,753 sq km; Borneo 751,929 sq km
top ten largest islands: Greenland 2,166,086 sq km; New Guinea (Indonesia, Papua New Guinea) 785,753 sq km; Borneo (Brunei, Indonesia, Malaysia) 751,929 sq km; Madagascar 587,713 sq km; Baffin Island (Canada) 507,451 sq km; Sumatra (Indonesia) 472,784 sq km; Honshu (Japan) 227,963 sq km; Victoria Island (Canada) 217,291 sq km; Great Britain (United Kingdom) 209,331 sq km; Ellesmere Island (Canada) 196,236 sq km
top ten longest mountain ranges (land-based): Andes (Venezuela, Colombia, Ecuador, Peru, Bolivia, Chile, Argentina) 7,000 km; Rocky Mountains (Canada, US) 4,830 km; Great Dividing Range (Australia) 3,700 km; Transantarctic Mountains (Antarctica) 3,500 km; Kunlun Mountains (China) 3,000 km; Ural Mountains (Russia, Kazakhstan) 2,640 km; Atlas Mountains (Morocco, Algeria, Tunisia) 2,500 km; Appalachian Mountains (Canada, US) 2,400 km; Himalayas (Pakistan, Afghanistan, India, China, Nepal, Bhutan) 2,300 km; Altai Mountains (Kazakhstan, Russia, Mongolia) 2,000 km; note - lengths are approximate; if oceans are included, the Mid-Ocean Ridge is by far the longest mountain range at 40,389 km
top ten largest forested countries (sq km and percent of land): Russia 8,149,310 (49.8%); Brazil 4,935,380 (58.9%); Canada 3,470,690 (38.2%); United States 3,103,700 (33.9%); China 2,098,640 (22.3%); Democratic Republic of the Congo 1,522,670 (67.2%); Australia 1,250,590 (16.3%); Indonesia 903,250 (49.9%); Peru 738,054 (57.7%); India 708,600 (23.8%) (2016 est.)
top ten most densely forested countries (percent of land): Suriname (98.3%), Federated States of Micronesia (91.9%), Gabon (90%), Seychelles (88.4%), Palau (87.6%), Guyana (83.9%), Laos (82.1%), Solomon Islands (77.9%), Papua New Guinea (74.1%), Finland (73.1%) (2016 est.)
top ten largest (non-polar) deserts: Sahara (Algeria, Chad, Egypt, Libya, Mali, Mauritania, Niger, Western Sahara, Sudan, Tunisia) 9,200,000 sq km; Arabian (Saudi Arabia, Iraq, Jordan, Kuwait, Oman, Qatar, United Arab Emirates, Yemen) 2,330,000 sq km; Gobi (China, Mongolia) 1,295,000 sq km; Kalahari (Botswana, Namibia, South Africa) 900,000 sq km; Patagonian (Argentina) 673,000 sq km; Syrian (Syria, Iraq, Jordan, Saudi Arabia) 500,000 sq km; Chihuahuan (Mexico) 362,000 sq km; Kara-Kum (Turkmenistan) 350,000 sq km; Great Victoria (Australia) 348,750 sq km; Great Basin (United States) 343,169 sq km; note - if the two polar deserts are included, they would rank first and second: Antarctic Desert 14,200,000 sq km and Arctic Desert 13,900,000 sq km
ten smallest independent countries: Holy See (Vatican City) 0.44 sq km; Monaco 2 sq km; Nauru 21 sq km; Tuvalu 26 sq km; San Marino 61 sq km; Liechtenstein 160 sq km; Marshall Islands 181 sq km; Saint Kitts and Nevis 261 sq km; Maldives 298 sq km; Malta 316 sq km
the land boundaries in the world total 251,060 km (not counting shared boundaries twice); two nations, China and Russia, each border 14 other countries note: 46 nations and other areas are landlocked, these include: Afghanistan, Andorra, Armenia, Austria, Azerbaijan, Belarus, Bhutan, Bolivia, Botswana, Burkina Faso, Burundi, Central African Republic, Chad, Czechia, Eswatini, Ethiopia, Holy See (Vatican City), Hungary, Kazakhstan, Kosovo, Kyrgyzstan, Laos, Lesotho, Liechtenstein, Luxembourg, Macedonia, Malawi, Mali, Moldova, Mongolia, Nepal, Niger, Paraguay, Rwanda, San Marino, Serbia, Slovakia, South Sudan, Switzerland, Tajikistan, Turkmenistan, Uganda, Uzbekistan, West Bank, Zambia, Zimbabwe; two of these, Liechtenstein and Uzbekistan, are doubly landlocked
Coastline:
356,000 km
note: 95 nations and other entities are islands that border no other countries, they include: American Samoa, Anguilla, Antigua and Barbuda, Aruba, Ashmore and Cartier Islands, The Bahamas, Bahrain, Baker Island, Barbados, Bermuda, Bouvet Island, British Indian Ocean Territory, British Virgin Islands, Cabo Verde, Cayman Islands, Christmas Island, Clipperton Island, Cocos (Keeling) Islands, Comoros, Cook Islands, Coral Sea Islands, Cuba, Curacao, Cyprus, Dominica, Falkland Islands (Islas Malvinas), Faroe Islands, Fiji, French Polynesia, French Southern and Antarctic Lands, Greenland, Grenada, Guam, Guernsey, Heard Island and McDonald Islands, Howland Island, Iceland, Isle of Man, Jamaica, Jan Mayen, Japan, Jarvis Island, Jersey, Johnston Atoll, Kingman Reef, Kiribati, Madagascar, Maldives, Malta, Marshall Islands, Mauritius, Mayotte, Federated States of Micronesia, Midway Islands, Montserrat, Nauru, Navassa Island, New Caledonia, New Zealand, Niue, Norfolk Island, Northern Mariana Islands, Palau, Palmyra Atoll, Paracel Islands, Philippines, Pitcairn Islands, Puerto Rico, Saint Barthelemy, Saint Helena, Saint Kitts and Nevis, Saint Lucia, Saint Pierre and Miquelon, Saint Vincent and the Grenadines, Samoa, Sao Tome and Principe, Seychelles, Singapore, Sint Maarten, Solomon Islands, South Georgia and the South Sandwich Islands, Spratly Islands, Sri Lanka, Svalbard, Taiwan, Tokelau, Tonga, Trinidad and Tobago, Turks and Caicos Islands, Tuvalu, Vanuatu, Virgin Islands, Wake Island, Wallis and Futuna
[see also: Coastline country ranks ]
[see also: Coastline country ranks ]
a variety of situations exist, but in general, most countries make the following claims measured from the mean low-tide baseline as described in the 1982 UN Convention on the Law of the Sea: territorial sea - 12 nm, contiguous zone - 24 nm, and exclusive economic zone - 200 nm; additional zones provide for exploitation of continental shelf resources and an exclusive fishing zone; boundary situations with neighboring states prevent many countries from extending their fishing or economic zones to a full 200 nm
Climate:
a wide equatorial band of hot and humid tropical climates, bordered north and south by subtropical temperate zones that separate two large areas of cold and dry polar climates
Ten Driest Places on Earth (Average Annual Precipitation):
McMurdo Dry Valleys, Antarctica 0 mm (0 in)
Arica, Chile 0.76 mm (0.03 in)
Al Kufrah, Libya 0.86 mm (0.03 in)
Aswan, Egypt 0.86 mm (0.03 in)
Luxor, Egypt 0.86 mm (0.03 in)
Ica, Peru 2.29 mm (0.09 in)
Wadi Halfa, Sudan 2.45 mm (0.1 in)
Iquique, Chile 5.08 mm (0.2 in)
Pelican Point, Namibia 8.13 mm (0.32 in)
El Arab (Aoulef), Algeria 12.19 mm (0.48 in)
Ten Wettest Places on Earth (Average Annual Precipitation):
Mawsynram, India 11,871 mm (467.4 in)
Cherrapunji, India 11,777 mm (463.7 in)
Tutunendo, Colombia 11,770 mm (463.4 in)
Cropp River, New Zealand 11,516 mm (453.4 in)
San Antonia de Ureca, Equatorial Guinea 10,450 mm (411.4 in)
Debundsha, Cameroon 10,299 mm (405.5 in)
Big Bog, US (Hawaii) 10,272 mm (404.4 in)
Mt Waialeale, US (Hawaii) 9,763 mm (384.4 in)
Kukui, US (Hawaii) 9,293 mm (365.9 in)
Emeishan, China 8,169 mm (321.6 in)
Ten Coldest Places on Earth (Lowest Average Monthly Temperature):
Verkhoyansk, Russia (Siberia) -47°C (-53°F) January
Oymyakon, Russia (Siberia) -46°C (-52°F) January
Eureka, Canada -38.4°C (-37.1°F) February
Isachsen, Canada -36°C (-32.8°F) February
Alert, Canada -34°C (-28°F) February
Kap Morris Jesup, Greenland -34°C (-29°F) March
Cornwallis Island, Canada -33.5°C (-28.3°F) February
Cambridge Bay, Canada -33.5°C (28.3°F) February
Ilirnej, Russia -33°C (-28°F) January
Resolute, Canada -33°C (-27.4°F) February
Ten Hottest Places on Earth (Highest Average Monthly Temperature):
Death Valley, US (California) 39°C (101°F) July
Iranshahr, Iran 38.3°C (100.9°F) June
Ouallene, Algeria 38°C (100.4°F) July
Kuwait City, Kuwait 37.7°C (100°F) July
Medina, Saudi Arabia 36°C (97°F) July
Buckeye, US (Arizona) 34°C (93°F) July
Jazan, Saudi Arabia 33°C (91°F) June
Al Kufrah, Libya 31°C (87°F) July
Alice Springs, Australia 29°C (84°F) January
Tamanrasset, Algeria 29°C (84°F) June
Terrain:
tremendous variation of terrain on each of the continents; check the World 'Elevation' entry for a compilation of terrain extremes; the world's ocean floors are marked by mid-ocean ridges while the ocean surfaces form a dynamic, continuously changing environment; check the 'Terrain' field and its 'major surface currents' subfield under each of the five ocean (Arctic, Atlantic, Indian, Pacific, and Southern) entries for further information on oceanic environs
Ten Cave Superlatives:
compiled from "Geography - note(s)" under various country entries where more details may be found
largest cave: Son Doong in Phong Nha-Ke Bang National Park, Vietnam is the world's largest cave (greatest cross sectional area) and is the largest known cave passage in the world by volume; it currently measures a total of 38.5 million cu m (about 1.35 billion cu ft); it connects to Thung cave (but not yet officially); when recognized, it will add an additional 1.6 million cu m in volume
largest ice cave: the Eisriesenwelt (Ice Giants World) inside the Hochkogel mountain near Werfen, Austria is the world's largest and longest ice cave system at 42 km (26 mi)
longest cave: Mammoth Cave, in west-central Kentucky, is the world's longest known cave system with more than 650 km (405 mi) of surveyed passageways
longest salt cave: the Malham Cave in Mount Sodom in Israel is the world's longest salt cave at 10 km (6 mi); its survey is not complete and its length will undoubtedly increase
longest underwater cave: the Sac Actun cave system in Mexico at 348 km (216 mi) is the longest underwater cave in the world and the second longest cave worldwide
longest lava tube cave: Kazumura Cave on the island of Hawaii is the world's longest and deepest lava tube cave; it has been surveyed at 66 km (41 mi) long and 1,102 m (3,614 ft) deep
deepest cave: Veryovkina Cave in the Caucasus country of Georgia is the world's deepest cave, plunging down 2,212 m (7,257 ft)
deepest underwater cave: the Hranice Abyss in Czechia is the world's deepest surveyed underwater cave at 404 m (1,325 ft); its survey is not complete and it could end up being some 800-1,200 m deep
largest cave chamber: the Miao Room in the Gebihe cave system at China's Ziyun Getu He Chuandong National Park encloses some 10.78 million cu m (380.7 million cu ft) of volume
largest bat cave: Bracken Cave outside of San Antonio, Texas is the world's largest bat cave; it is the summer home to the largest colony of bats in the world; an estimated 20 million Mexican free-tailed bats roost in the cave from March to October making it the world's largest known concentration of mammals
Elevation:
mean elevation: 840 m
[see also: Elevation - mean elevation country ranks ]
lowest point:
Denman Glacier (Antarctica) more than -3,500 m (in the oceanic realm, Challenger Deep in the Mariana Trench is the lowest point, lying -10,924 m below the surface of the Pacific Ocean)
highest point:
Mount Everest 8,850 m
top ten highest mountains (measured from sea level): Mount Everest (China-Nepal) 8,850 m; K2 (Pakistan) 8,611 m; Kanchenjunga (India-Nepal) 8,598 m; Lhotse (Nepal) 8,516 m; Makalu (China-Nepal) 8,463 m; Cho Oyu (China-Nepal) 8,201 m; Dhaulagiri (Nepal) 8,167 m; Manaslu (Nepal) 8,163 m; Nanga Parbat (Pakistan) 8,125 m; Anapurna (Nepal) 8,091 m; note - Mauna Kea (United States) is the world's tallest mountain as measured from base to summit; the peak of this volcanic colossus lies on the island of Hawaii, but its base begins more than 70 km offshore and at a depth of about 6,000 m; total height estimates range from 9,966 m to 10,203 m
top ten highest island peaks: Puncak Jaya (New Guinea) 4,884 m (Indonesia)*; Mauna Kea (Hawaii) 4,207 m (United States); Gunung Kinabalu (Borneo) 4,095 m (Malaysia)*; Yu Shan (Taiwan) 3,952 (Taiwan)*; Mount Kerinci (Sumatra) 3,805 m (Indonesia); Mount Erebus (Ross Island) 3,794 (Antarctica); Mount Fuji (Honshu) 3,776 m (Japan)*; Mount Rinjani (Lombok) 3,726 m (Indonesia); Aoraki-Mount Cook (South Island) 3,724 m (New Zealand)*; Pico de Teide (Tenerife) 3,718 m (Spain)*; note - * indicates the highest peak for that Factbook entry
highest point on each continent: Asia - Mount Everest (China-Nepal) 8,850 m; South America - Cerro Aconcagua (Argentina) 6,960 m; North America - Denali (Mount McKinley) (United States) 6,190 m; Africa - Kilimanjaro (Tanzania) 5,895 m; Europe - El'brus (Russia) 5,633 m; Antarctica - Vinson Massif 4,897 m; Australia - Mount Kosciuszko 2,229 m
highest capital on each continent: South America - La Paz (Bolivia) 3,640 m; Africa - Addis Ababa (Ethiopia) 2,355 m; Asia - Thimphu (Bhutan) 2,334 m; North America - Mexico City (Mexico) 2,240 m; Europe - Andorra la Vella (Andorra) 1,023 m; Australia - Canberra (Australia) 605 m
lowest point on each continent: Antarctica - Denman Glacier more than -3,500 m; Asia - Dead Sea (Israel-Jordan) -431 m; Africa - Lac Assal (Djibouti) -155 m; South America - Laguna del Carbon (Argentina) -105 m; North America - Death Valley (United States) -86 m; Europe - Caspian Sea (Azerbaijan-Kazakhstan-Russia) -28 m; Australia - Lake Eyre -15 m
lowest capital on each continent: Asia - Baku (Azerbaijan) -28 m; Europe - Amsterdam (Netherlands) -2 m; Africa - Banjul (Gambia); Bissau (Guinea-Bissau), Conakry (Guinea), Djibouti (Djibouti), Libreville (Gabon), Male (Maldives), Monrovia (Liberia), Tunis (Tunisia), Victoria (Seychelles) 0 m; North America - Basseterre (Saint Kitts and Nevis), Kingstown (Saint Vincent and the Grenadines), Panama City (Panama), Port of Spain (Trinidad and Tobago), Roseau (Dominica), Saint John's (Antigua and Barbuda), Santo Domingo (Dominican Republic) 0 m; South America - Georgetown (Guyana) 0 m; Australia - Canberra (Australia) 605 m
Natural resources:
the rapid depletion of nonrenewable mineral resources, the depletion of forest areas and wetlands, the extinction of animal and plant species, and the deterioration in air and water quality pose serious long-term problems
Irrigated land:
3,242,917 sq km
(2012 est.)
[see also: Irrigated land country ranks ]
[see also: Irrigated land country ranks ]
Population distribution:
six of the world's seven continents are widely and permanently inhabited; Asia is easily the most populous continent with about 60% of the world's population (China and India together account for over 35%); Africa comes in second with over 15% of the earth's populace, Europe has about 10%, North America 8%, South America almost 6%, and Oceania less than 1%; the harsh conditions on Antarctica prevent any permanent habitation
Natural hazards:
large areas subject to severe weather (tropical cyclones); natural disasters (earthquakes, landslides, tsunamis, volcanic eruptions)
volcanism: volcanism is a fundamental driver and consequence of plate tectonics, the physical process reshaping the Earth's lithosphere; 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 Decade 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); see second note under "Geography - note"
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 biodiversity; soil degradation, soil depletion, erosion; ozone layer depletion; waste disposal; global warming becoming a greater concern
Geography - note:
note 1: the world is now thought to be about 4.55 billion years old, just about one-third of the 13.8-billion-year age estimated for the universe; the earliest widely accepted date for life appearing on earth is 3.48 billion years ago, but this date is conservative and may get pushed back further
note 2: although earthquakes can strike anywhere at any time, the vast majority occur in three large zones of the earth; the world's greatest earthquake belt, the Circum-Pacific Belt (popularly referred to as the Ring of Fire), is the zone of active volcanoes and earthquake epicenters bordering the Pacific Ocean; about 90% of the world's earthquakes (81% of the largest earthquakes) and some 75% of the world's volcanoes occur within the Ring of Fire; the belt extends northward from Chile, along the South American coast, through Central America, Mexico, the western US, southern Alaska and the Aleutian Islands, to Japan, the Philippines, Papua New Guinea, island groups in the southwestern Pacific, and New Zealand
the second prominent belt, the Alpide, extends from Java to Sumatra, northward along the mountains of Burma, then eastward through the Himalayas, the Mediterranean, and out into the Atlantic Ocean; it accounts for about 17% of the world's largest earthquakes; the third important belt follows the long Mid-Atlantic Ridge
