World Geography — 09 Aug 2026

Some Facts About The Earth

Size of the Earth

• Diameter: 12742 km
• Radius: 6371 km
• Surface Area: 510.1 million km²
• Land Area: 148.9 million km²
• Distance from Sun: 149.59 million km (source: NASA)
• Distance from Moon: 384400 km

Some Basic Geographical Terms

• Longitudes → imaginary lines running from North to South of the globe, they specify the position of a point as per East and West.
• Latitudes → imaginary lines running from East to West which specify location of a point with respect to the North or South and with respect to the distance of it from the Equator.
• Equator → the earth is divided into the Northern and Southern Hemisphere by the latitudinal lines, the imaginary line running through the centre of the earth is the equator and it's at 0 degree latitude.
• Prime Meridian → the point where the longitude equals to 0 degree and it is used in coordination and finding locations of points on Earth. This line divides Earth into Eastern and Western Hemispheres.
• International Date Line (IDL) → an imaginary line running from North to South and the day and date change as you cross this line; going westward would increase the day and date by one and vice versa for going eastward.
• Greenwich Mean Time (GMT) → The time calculated by the Royal Observatory in Greenwich, London; GMT is also used synonymously with UTC which is Coordinated Universal Time.

Countries on Equator

Ecuador, Colombia, Brazil, Sao Tome & Principe, Gabon, Republic of the Congo, Democratic Republic of the Congo, Uganda, Kenya, Somalia, Maldives, Indonesia, Kiribati.

Layers of Atmosphere

(Note: Temperature decreases with height in the troposphere/mesosphere layers; increases with height in the thermosphere.)

Four Layers of Earth

1. The Crust (Oceanic and Continental crust)
2. The Mantle — thickest layer of Earth; Magma is present in this layer
3. Outer core — liquid
4. Inner core — solid

Three Main Types of Rocks

• Igneous Rocks: Formed deep inside the earth upon cooling of magma. Often have large crystals. Common types: andesite, granite, dacite, diorite, peridotite, gabbros, tuff, volcanic bomb.
• Sedimentary Rocks: Porous rocks formed by solidification of sediments; from organic remains (like limestone) or solidification of other rocks. Common types: conglomerate, sandstone, mudrocks, limestone.
• Metamorphic Rocks: Formed as a result of change of igneous and sedimentary rocks; can form below and above the surface. Thermal metamorphism occurs near magma (partial melting). Dynamic metamorphism occurs deep below the surface under massive pressure. Common types: amphibolite, schist, marble, quartzite, slate, hornfels, phyllite.

Three Main Geographical Zones

• Torrid Zone: Between the Tropic of Cancer and Tropic of Capricorn (23.5°N to 23.5°S).
• Frigid Zone: Areas around North and South poles within the Polar circles.
• Temperate Zone: Between Tropic of Cancer and Arctic Circle, or between Tropic of Capricorn and Antarctic Circle.

Surface Area, Volume, and Average Depth of Oceans

For this calculation, Southern Ocean includes all marine waters south of 60°S. Data source: Eakins, B.W. and G.F. Sharman, Volumes of the World's Oceans from ETOPO1, NOAA National Geophysical Data Center, Boulder, Colorado.

Quick Facts about Seas and Oceans

• Pacific Ocean is the deepest ocean in the world.
• Mariana Trench is the deepest trench on Earth, located in the Pacific Ocean.
• Mid-Atlantic Ridge is the longest mountain range, located in the Atlantic Ocean.
• Ring of Fire is situated in the Pacific Ocean region; it is a ring of volcanoes.
• North Pacific Ocean is considered the world's most polluted ocean.
• Red Sea is named for algae called Trichodesmium erythraeum found in the sea.
• Dead Sea is called "dead" due to high salinity making it impossible for macroscopic life to survive; it is also the saltiest sea in the world.
• Black Sea was deemed inhospitable before Greek colonization due to severe storms making it hard to navigate, and the storms make it look black.
• Indian Ocean & Atlantic Ocean meet at Cape of Good Hope (South Africa).
• Pacific Ocean & Atlantic Ocean meet at Cape Horn.
• Indian Ocean & Pacific Ocean meet at the Gulf of Alaska.
• Indian Ocean & Southern Ocean meet at Cape Leeuwin.
• Oceans cover 70% of the world's surface.

Biggest and Deepest Ocean: Pacific Ocean — deepest point is Challenger Deep (36,200 ft deep); largest ocean basin at 63 million sq miles, containing more than half of earth's free water.

Rivers of the World

Source for lengths: World Atlas

Important Note: According to the latest research, Amazon is considered the world's longest river, but your examiners might still consider the Nile as the longest.

River Thames is a world-famous river located in England.

List of Rivers Found in Canada: Mackenzie River, St Lawrence River, Fraser River, Yukon River, Columbia River, Nelson River.

List of Rivers Flowing through Washington DC

Important Facts about River Nile

• Longest river in the world, flowing about 6,650 kilometres, starting from Lake Victoria.
• Flows through the African Great Lakes, through the Sahara Desert, and empties into the Mediterranean Sea.
• Flows through 11 countries: Tanzania, Uganda, Rwanda, Burundi, Congo, Kenya, Ethiopia, Eritrea, South Sudan, Sudan, Egypt.
• Has three main tributaries: White Nile, Blue Nile, and Atbara.

Other River Facts

• Jordan is the most mentioned river in the Bible, considered a source of great fertility.
• The Greek epic poems "Iliad" and "Odyssey" — the most important part of Greek literature — were written by Homer.
• Industrial Revolution started with the invention of the steam engine, marking the transition from human power to machine power; also set the stage for inventions like the power/spinning loom.
• 8th Continent of the world: Called Zealandia, situated below New Zealand; confirmed in 2017.
• Oceania: Includes Australasia, Polynesia, Micronesia, and Melanesia.
• Andes Mountains: Longest mountain range, 7,200 km long, spread over Peru, Chile, Argentina, Colombia, Venezuela, Ecuador, and Bolivia.
• Niagara Falls is in the North American continent.
• Trout Lake is in Ontario, Canada; popular for fishing — Trout, Musky, Largemouth Bass, Panfish, Walleye, Smallmouth Bass, Northern Pike.

Delta

A river delta is a landform that forms at the mouth of a river, where the river flows into an ocean, sea, estuary, lake, or reservoir.

Famous Deltas

Note: River Narmada and St Lawrence River are without a delta.

Largest Lakes

• Lake Superior (Canada) is the world's largest freshwater lake by surface area.
• Caspian Sea is the world's largest salt lake; also the world's largest lake by surface area and volume if excluding saltwater characteristic.
• Kariba Lake (Zambia, Zimbabwe) is the world's largest artificial lake.
• Dead Sea is the lowest lake in the world, located in Israel and Jordan.
• Titicaca (Peru) is the world's highest lake, 12,500 feet above sea level.
• Great Bear Lake is the largest lake in Canada.
• Lake Tana is a famous lake of Ethiopia.
• Pink Lake (Lake Hilier) is located in Australia.
• Red Lake is situated in America.

Busiest Canals of the World

World's Largest Peninsulas

A Peninsula is a portion of land projected into a body of water such that it is surrounded by water except the part connecting it to the mainland.

Ocean Terminology / Water Bodies Terminologies

• Lagoon: A shallow body of water, like a pond or lake, separated from the main body of water.
• High Tide: The maximum elevation reached by each rising tide.
• Hurricane: An intense tropical cyclone with winds that move counterclockwise around a low-pressure system. Maximum sustained winds of 74 mph or greater.
• Marsh: An area of soft, wet or periodically inundated land, generally treeless, characterized by grasses and other low growth.
• Mean High Water: The average height of the high waters recorded at a given place over a 19-year period.
• Estuary: The part of a river affected by tides; the region near a river mouth where freshwater mixes with saltwater of the sea.
• Estuarine: Pertaining to an estuary.

World's Largest Inland Water Bodies by Area

Names of Straits, their Location, and the Water Bodies They Connect

• World's longest strait is Strait of Malacca.
• World's busiest strait is Strait of Dover.
• World's shortest strait is Bosporus.

Facts Related to Continents

• Seven continents: Africa, Antarctica, Asia, Europe, North America, South America, Australia/Oceania.
• Asia is the largest continent by size and population.
• Australia is the smallest continent by size and population.
• Asia has the second-most countries: 48.