Weathering breaks down or chemically changes rock where it is, while erosion removes and transports material from one place to another. A cracked boulder that has not moved is an example of weathering; sand carried downstream by a river is undergoing erosion. The two processes often work together,…
Erosion is the movement of rock, soil, and sediment from one place to another by forces such as water, wind, and moving ice. Water carries particles through rainfall, runoff, rivers, and waves; wind lifts and rolls loose material; glaciers scrape and pull rock from the ground as they…
An ice age is a long interval when Earth is cold enough for large, permanent ice sheets to exist on land. Ice ages contain colder glacial periods and warmer interglacial periods, so an ice age does not mean the whole planet stays frozen. Earth is still within the…
Glaciers form where snow survives from year to year, becomes denser, turns into glacier ice, and grows thick enough to deform and flow under gravity. They move mainly through internal deformation within the ice and movement at the bed, which can include basal sliding over rock or water-rich…
Mount Everest is the highest mountain above mean sea level at 8,848.86 meters (29,032 feet), followed by K2 at 8,611 meters and Kangchenjunga at 8,586 meters. Every one of Earth’s 14 main peaks above 8,000 meters lies in just two Asian mountain systems: the Himalaya and Karakoram. That…
Deserts form where a region receives too little usable moisture over long periods. The cause may be sinking dry air, mountain barriers, cold ocean currents, great distance from moisture sources, or extreme cold. Many deserts develop through a combination of these processes working together. Low rainfall is only…
Lake Baikal in Russia is the deepest surface lake on Earth, reaching about 1,642 metres (5,387 feet) at its deepest measured point. Lake Tanganyika follows at about 1,470 metres, while the saline Caspian Sea reaches about 1,025 metres and is commonly treated by geographers as a lake despite…
The world’s largest lake by area is the Caspian Sea, an inland water body so wide that many maps label it with the word “sea.” By common reference ranking, it is followed by Lake Superior, Lake Victoria, Lake Huron, and Lake Michigan. A lake’s surface area means the…
A lake is an inland body of water held within a land basin, while a sea is usually part of the connected ocean system and is often partly enclosed by land. Saltiness and size can offer clues, but neither one reliably decides whether a water body is a…
A river basin is the land area where rain, snowmelt, streams, and connected surface water drain toward the same outlet. Small channels join tributaries, tributaries feed a main river, and gravity moves much of that water toward a lake, inland sink, sea, or ocean. The surrounding high ground…
The Nile is commonly listed as the world’s longest river at about 6,650 km, while the Amazon follows close behind at about 6,400 km in many standard reference tables. River length is not as simple as tracing one blue line on a map. It depends on which source…
The world’s largest desert is Antarctica, not the Sahara, because a desert is defined mainly by dryness, not heat. The Arctic Desert ranks second, and the Sahara is the largest hot desert on Earth. Deserts are places where water is scarce for plants, soils, rivers, animals, and people.…
Mountains form when Earth’s crust is shortened, stretched, lifted, or repeatedly covered by erupted material. Fold mountains grow mainly from compression and crustal thickening, fault-block mountains from movement along large faults during extension, and volcanic mountains from lava, ash, and other erupted material accumulating around vents. These processes…
Shield volcanoes are broad, gently sloping mountains built mainly by fluid lava, stratovolcanoes are taller cones formed through repeated eruptions of lava and fragmented volcanic material, and cinder cones are smaller, steep-sided piles of scoria and other tephra around a vent. Their different shapes reflect differences in magma…
Volcanoes form when magma rises from inside Earth and reaches the surface, but the magma is not produced everywhere in the same way. Most volcanism is linked to convergent or divergent plate boundaries, while hotspots can feed volcanoes within a plate or add extra magma where a hotspot…
Earthquakes often get described with two different kinds of numbers: magnitude and intensity. They sound similar, but they answer different questions. Magnitude describes the size of the earthquake at its source. Intensity describes the strength of shaking at a specific place. Understanding this difference helps people read alerts,…
Earth’s surface looks solid, but it is built from moving pieces called tectonic plates. These slabs of the lithosphere (crust plus the uppermost mantle) slide over a softer layer beneath, reshaping continents, building mountains, opening oceans, and triggering earthquakes. Plate tectonics is the unifying theory that explains why…
Earth has one connected global ocean, but for navigation, science, and everyday language it’s often described as five major ocean basins: the Pacific, Atlantic, Indian, Southern, and Arctic. Each one has its own shape, depth profile, and signature role in climate and ecosystems—yet all are linked by currents…
Continents are Earth’s biggest land regions—huge, varied spaces where geology, climate, and human history interact on a planetary scale. When people say “the continents,” they usually mean seven broad areas: Asia, Africa, North America, South America, Antarctica, Europe, and Australia (often grouped with the wider region called Oceania).…