50 Fun Facts About Landforms

Which continent, the driest on Earth, holds a desert so large it outranks even the Sahara in area?

Antarctica is the largest desert on Earth, because a desert is defined by how little precipitation falls, not by heat. Its interior gets less than 50 mm a year, leaving the Sahara as the largest hot desert.

Which Hawaiian volcano, measured from its base on the ocean floor, is often called Earth's tallest mountain?

Mauna Kea rises more than 9,000 metres from its underwater base, but most of that height is hidden. Only about 4,200 metres of it stands above the waves.

Which landmass ranks as the world's largest island, since Australia is counted as a continent instead?

Greenland is the world's largest island, and an ice sheet buries about four-fifths of it. Australia is bigger still, but geographers treat it as a mainland in its own right.

Which landform, such as Florida or Italy, juts out from a mainland and is mostly surrounded by water?

Peninsula comes from the Latin words paene, 'almost', and insula, 'island'. That is just what one looks like on a map: land tied to the mainland on only one side.

Which icicle-shaped mineral formations hang from the ceilings of limestone caves, built up by dripping water?

Stalactites cling to the ceiling, while stalagmites grow up from the floor beneath them. Most grow only a fraction of a millimetre a year, and a pair can eventually fuse into a single column.

Which lake bordering Jordan and Israel has shores that are the lowest dry land on Earth?

The Dead Sea has a shoreline more than 430 metres below sea level. Its water is nearly ten times as salty as the ocean, so dense that swimmers simply float.

Which river spent millions of years carving Arizona's Grand Canyon, cutting more than a mile down into the rock?

The Colorado has been cutting through the area for an estimated five to six million years. At the bottom of the gorge it has exposed rocks close to two billion years old.

Which landform builds up from dropped sediment where a river such as the Nile or Mississippi reaches the sea?

A delta gets its name from the Nile's, whose triangular shape resembles the Greek capital letter of the same name. The river slows at the coast and drops its mud, building new land.

What gouged out the deep basins that now hold North America's Great Lakes?

Glaciers carved the basins, and when the ice sheets retreated around 14,000 years ago their meltwater filled the hollows. That makes the Great Lakes youngsters in geological terms.

Which zone of volcanoes and frequent earthquakes, about 40,000 km long, surrounds most of the Pacific Ocean?

The Ring of Fire holds around two-thirds of the world's volcanoes and produces about 90% of its earthquakes. It marks the edges where ocean plates are forced down beneath their neighbours.

Which narrow landform links two larger landmasses, as Panama does between North and South America?

The isthmus at Panama is thought to have formed around three million years ago, joining two continents. Animals then crossed in both directions, an event called the Great American Interchange.

Which term describes a chain or cluster of islands, such as Hawaii, Japan or the Philippines?

Archipelago began as the Italian name for the Aegean Sea, which is crowded with islands, before it came to mean any such group. Indonesia is the largest country made of one, with more than 17,000 islands.

Which type of landform is Tibet's vast highland, nicknamed the Roof of the World for its great height?

A plateau is high ground with a broad, fairly flat top, and Tibet's is the largest and highest on Earth. It averages more than 4,500 metres above sea level.

Which mountain, known in Nepal as Sagarmatha, has the highest summit above sea level on Earth?

Everest is capped with marine limestone that holds fragments of fossil sea creatures. The rock formed on an ancient seabed before being lifted nearly nine kilometres into the sky.

Which coral system off Queensland, Australia, is the largest structure on Earth built by living organisms?

The Great Barrier Reef is made up of more than 2,900 separate reefs stretching over 2,300 km, and it can be seen from space. Billions of tiny coral polyps built all of it.

Which Venezuelan waterfall, named after a pilot who flew over it, is the world's tallest uninterrupted drop?

Angel Falls drops 979 metres from a flat mountaintop. Jimmie Angel later wrecked his plane trying to land up there, and his party needed 11 days to walk back down.

Which undersea feature in the western Pacific holds Challenger Deep, the deepest known point in any ocean?

The Mariana Trench plunges nearly 11 km, where the water presses down with over 1,000 times the air pressure at the surface. People first reached the bottom in 1960, aboard the bathyscaphe Trieste.

Which narrow body of water links two larger ones, as at Gibraltar between the Atlantic and the Mediterranean?

A strait can be startlingly slim: at Gibraltar, only about 14 km of water separates Europe from Africa at the narrowest point.

Which term describes a river that flows into a larger one, as the Missouri does when it meets the Mississippi?

A tributary can outgrow its reputation: the Missouri is the longest river in the United States, yet it gives up its name when it meets the Mississippi.

Which kind of hot spring erupts jets of boiling water and steam, as Old Faithful does in Yellowstone?

A geyser needs a rare combination of water, heat and natural plumbing, so only a few places on Earth have them. Yellowstone holds roughly 300 to 500, and Old Faithful erupts about every 90 minutes.

Which ring-shaped coral island, common in the Maldives and Marshall Islands, encircles a central lagoon?

An atoll, in Charles Darwin's 1842 explanation, is what remains when a volcanic island sinks and its fringe of coral keeps growing upward. Most are found in the Pacific and Indian oceans.

Which fertile spot in a desert, fed by springs or underground water, served caravans as a place to restock?

An oasis decided where trade could go, because caravans had to travel from one to the next to refill on water and food. The water rises naturally from springs or is drawn up through wells.

Which long, narrow sea inlet with steep sides is so common in Norway that nearly 1,200 line its coast?

A fjord is a valley that ice gouged out below sea level, so the sea flooded in once the ice melted. Norway's Sognefjord reaches as much as 1,300 metres deep.

Which isolated, steep-sided hill has a flat top narrower than its height, like the Mittens of Monument Valley?

A butte is taller than it is wide, the rule of thumb that separates it from a broader mesa. The word comes from the French for a knoll.

Which coastal feature, like the mouth of the Thames, forms where a river's fresh water mixes with salty sea?

An estuary is brackish, saltier than a river but fresher than the sea. The mixing loads the water with nutrients, making these places some of the most productive natural habitats in the world.

Which bowl-shaped hollow, left when an emptied volcano collapses, holds Oregon's Crater Lake?

A caldera forms when an eruption drains the chamber beneath a volcano and the summit caves in. Mount Mazama did just that several thousand years ago, leaving the deepest lake in the United States.

Which mountain range, the longest on any continent, runs through seven countries?

The Andes run down the western edge of South America, where an oceanic plate is sliding beneath the continent. That slow collision also feeds the world's highest volcanoes.

Which lake, the deepest on Earth, holds more water than all of North America's Great Lakes combined?

Lake Baikal plunges 1,642 metres and holds roughly a fifth of the world's unfrozen fresh water. It is also the oldest lake on Earth, at 25 to 30 million years.

Which South American river carries more water to the sea than the next seven largest rivers combined?

The Amazon pours out more than 200,000 cubic metres of water every second, the greatest flow of any river. Whether it or the Nile is the longest remains disputed.

Which pit opens when dissolving limestone lets the ground above collapse, as often happens in Florida?

A sinkhole can sag slowly or drop in a moment when a cave roof gives way. In Mexico's Yucatán the water-filled ones are called cenotes, and the Maya cast offerings into them.

Which landmass ploughed north into Asia, crumpling the crust between them into the Himalayas?

India is still pushing into Asia at a few centimetres a year. The squeeze keeps lifting the Himalayas and sets off the region's great earthquakes.

Which island nation sits on the Mid-Atlantic Ridge, where the Eurasian and North American plates are moving apart?

Iceland is one of the few places where that mostly underwater ridge rises above the waves. The island is geologically young, at 16 to 18 million years old.

Which chain of lowlands, named by geologist John Walter Gregory, runs from Syria through East Africa to Mozambique?

The Great Rift Valley stretches about 6,500 km. Along its African part the continent is slowly tearing in two, as the Somali and Nubian plates pull apart by a few millimetres a year.

Which fault, where two plates grind sideways past each other, runs about 1,200 km through California?

The San Andreas forms part of the boundary between the Pacific and North American plates. Its northern stretch ruptured in 1906, in the earthquake that wrecked San Francisco.

Which supercontinent, first proposed by Alfred Wegener, joined nearly all of Earth's land before breaking apart?

Pangaea began to break apart during the age of the dinosaurs, and its pieces drifted into the continents on modern maps. The close fit of the coastlines on either side of the Atlantic was an early clue.

Which process carries loosened rock and soil away by wind, water or ice, unlike weathering, which moves nothing?

Erosion is the transport step, while weathering only breaks rock down where it sits. Rivers do most of theirs in flood, when faster water can carry a far heavier load.

Which letter matches the cross-section of an ice-carved valley such as Yosemite, unlike a river-cut one?

A U-shaped valley has steep, straight sides and a wide, flat floor, because ice scrapes out the whole trough. Rivers cut downward instead, leaving a narrower V.

Which curved lake, called a billabong in Australia, is left when a river cuts through the neck of a meander?

An oxbow forms because a river's bends grow more curved over time, until the water breaks through and takes the shortcut. The abandoned loop then silts up at both ends.

Which ice-scooped mountain hollow is called a corrie in Scotland and a cwm in Wales?

A cirque takes its name from the Latin circus. When the ice melts, the hollow often cradles a small lake called a tarn.

Which shallow underwater zone, usually less than 100 m deep, borders the land before the seabed plunges away?

A continental shelf is really the drowned edge of the land. During the last ice age the sea stood 100 to 120 metres lower, leaving much of this ledge as dry ground.

Which stretch of Northern Ireland's coast consists of about 40,000 interlocking basalt columns?

The Giant's Causeway is named for the legend that a giant built it as a road across the sea. Columns from the same lava flow surface at Fingal's Cave in Scotland.

Which South American desert, the driest outside the polar regions, is used to test instruments bound for Mars?

The Atacama has soil so nearly lifeless that it stands in for Mars. It sits in a double rain shadow, with mountain chains blocking moisture from both the Pacific and the Atlantic.

Which level expanse, such as Bonneville in Utah, is left behind when a desert lake evaporates?

A salt flat is made of the minerals once dissolved in the vanished water. The largest, Bolivia's Salar de Uyuni, covers more than 10,000 square km and becomes a vast mirror after rain.

Which ridge of rubble, dumped at the edge of an ice sheet, forms the twin spines of New York's Long Island?

A moraine is the rock and gravel an ice sheet carries along and drops where it melts. Long Island's pair were left behind some 21,000 years ago.

Which thin rock spires, also called fairy chimneys, are most abundant in Utah's Bryce Canyon?

Hoodoos are shaped mainly by frost: water freezes in cracks, expands and pries the rock apart. Bryce Canyon goes through more than 200 freeze-thaw cycles a year.

Which apron of sediment spreads out where a stream leaves a narrow canyon, a feature also found on Mars and Titan?

An alluvial fan builds up because water escaping the canyon spreads out, slows and drops its load. It is a simple result of gravity and geometry, which is why other worlds have them too.

Which isolated rock hill rising abruptly from a plain is also called a monadnock, after a New Hampshire mountain?

Inselberg is German for 'island mountain'. The harder rock is left standing alone after the softer rock around it has worn away into a plain.

Which process sinks one tectonic plate beneath another, building chains of explosive volcanoes above?

Subduction recycles old ocean floor back into the mantle. Water carried down with the sinking slab makes the volcanoes above especially explosive, Krakatoa and Vesuvius among them.

Which cave-riddled limestone terrain is named after a region between Slovenia and Italy?

Karst drains from below: rain seeps into cracks, widens them into caves, and whole rivers can vanish underground. The word reached European scholars in 1689, in an account of just such rivers.

Which ocean is the smallest and shallowest of the five, with an average depth of only about 1,000 metres?

The Arctic sits so far north that sea ice covers much of it all year and nearly all of it in winter. The ice is a big reason its geology is still poorly explored.