98 Fun Facts About Geology

Which Scottish scientist, author of the 1788 Theory of the Earth, is called the father of modern geology?

James Hutton saw land endlessly worn down and rebuilt, so he concluded the rocks showed 'no vestige of a beginning, no prospect of an end'.

What name did Alfred Wegener give the single landmass that he said later broke apart into today's continents?

Pangaea was Wegener's name for it, but he died on a Greenland expedition in 1930, decades before geologists accepted continental drift.

During his lifetime, continental drift pioneer Alfred Wegener was best known for work in which science?

Meteorology took him to Greenland in 1906, where he flew kites and tethered balloons to measure the polar air.

Clair Patterson dated the Earth at 4.55 billion years using lead from what?

A meteorite had kept its original lead since the solar system formed, while Earth's own rocks have been mixed and recycled by plate tectonics.

Earth's oldest known minerals, 4.4-billion-year-old zircons, come from the Jack Hills of which country?

Australia protected part of the Jack Hills on its National Heritage List in 2020, safeguarding the site of Earth's oldest known crystals.

Which volcano's AD 79 eruption buried the Roman towns of Pompeii and Herculaneum?

Mount Vesuvius killed the naturalist Pliny the Elder, who had sailed his fleet toward the eruption to rescue people on the coast.

Divers at Silfra swim through a fissure between two tectonic plates in which country?

Iceland's Silfra is fed by glacial meltwater that seeps through porous lava rock for 30 to 100 years, filtering it until it is exceptionally clear.

Which force do most geologists now consider the main driver of tectonic plate motion?

Slab pull comes from gravity: old seafloor grows cold and dense, and its sinking weight drags the whole plate along behind it.

Which Danish seismologist discovered Earth's solid inner core in 1936?

Inge Lehmann noticed faint P-waves arriving in the core's 'shadow zone', where none were expected, and explained them with a separate inner core.

The Mohorovičić discontinuity, or 'Moho', marks the boundary between which two layers of the Earth?

Crust and mantle meet at the Moho, which the US Project Mohole tried to drill down to from the seafloor until Congress cut its funding in 1966.

Which layer of the Earth is liquid and generates the Earth's magnetic field?

The outer core does not transmit seismic S-waves, which cannot travel through liquid, and that is how seismologists know it is molten.

In which epoch of the geologic time scale are we living, which began about 11,700 years ago?

Holocene is still official: in 2024 geologists rejected a proposal to follow it with a new 'Anthropocene' epoch marking human impact.

Which of these is one of the four eons that divide Earth's history?

The Hadean is named after Hades, the Greek underworld, for the intense heat of the newly formed Earth.

Nicolas Steno, a founder of modern geology, realised that 'tongue stones' found in rocks were actually what?

Fossil shark teeth sitting inside solid rock led Steno to ask how one solid could come to lie within another, the question behind his rules for rock layers.

Which principle popularised by Charles Lyell holds that 'the present is the key to the past'?

Uniformitarianism shaped young Charles Darwin, who took the first volume of Lyell's Principles of Geology aboard HMS Beagle in 1831.

The 1980 Mount St. Helens eruption began with the largest what above sea level in recorded history?

The landslide released the pressure on the volcano's magma, which then exploded through the sliding debris.

The Chicxulub crater lies buried beneath which peninsula?

Yucatán's asteroid strike set off earthquakes and giant tsunamis and spread a blanket of debris across the whole Earth.

Which element did Luis and Walter Alvarez find concentrated in the clay layer marking the end of the Cretaceous?

Iridium spikes in that clay all around the world, and in 1980 the Alvarez team argued it came from a giant asteroid impact.

On the Richter scale, each whole-number step multiplies the measured amplitude by what factor?

Ten times the amplitude per step, but magnitudes based only on wave amplitude misjudge very large quakes, so seismologists now prefer moment magnitude.

The most powerful earthquake ever recorded, magnitude 9.5 in 1960, struck which country?

Chile's 1960 quake sent tsunamis that killed people as far away as Hawaii and Japan.

On the Mohs hardness scale devised in 1812, which mineral sits at 1, the softest?

Talc sits at 1 because Mohs ranked his ten minerals simply by which one scratches another, not by any measured hardness.

Which mineral group makes up more than half of the Earth's crust?

Feldspar breaks down into clay minerals such as kaolinite as it weathers, so much of the clay in the ground began as feldspar.

The Giant's Causeway's roughly 40,000 interlocking columns are made of which volcanic rock?

Basalt columns at the Causeway were painted by Susanna Drury, and engravings of her pictures were copied into the French Encyclopédie.

The Grand Canyon's oldest rocks were exposed by which river cutting down through them?

The Colorado River cut through layer after layer as the land rose, exposing rocks nearly 2 billion years old.

The Mid-Atlantic Ridge is which type of plate boundary?

Divergent boundaries pull apart, so along the ridge new seafloor keeps forming as the plates separate about 2.5 cm a year.

Which scientist's 1950s maps of the Atlantic seafloor, made with Bruce Heezen, revealed a rift valley along its ridge?

Marie Tharp drew the maps from data Heezen gathered at sea, because women were then barred from working aboard research ships.

The San Andreas Fault marks the boundary between the North American Plate and which other?

The Pacific Plate moves northwest past North America along the fault, and a sudden slip in 1906 caused the great San Francisco earthquake.

Yellowstone's most recent supereruption left behind what kind of vast volcanic feature?

A caldera forms when the ground collapses into a magma chamber emptied by a giant eruption, and Yellowstone has three of them.

Which Canadian geophysicist proposed in 1963 that Hawaii formed as the seafloor moved over a hotspot?

J. Tuzo Wilson argued the moving plate carries each island away from a fixed hotspot until its volcanoes die, so the chain grows older to the northwest.

The Himalayas are still rising because of the collision of the Eurasian Plate with which other plate?

The Indian Plate carried India north until it hit Asia, and that collision is still pushing the peaks higher.

The Mariana Trench, the deepest place in the oceans, was formed by what process?

Subduction built the trench, and in 1960 the US Navy submersible Trieste descended to the bottom of its deepest point, the Challenger Deep.

After Krakatoa erupted in 1883, ash high in the sky made what look blue around the world at night?

The Moon looked blue because Krakatoa's ash particles scattered red light, and blue moons were seen in many places for months.

Which belt of volcanoes hosts most of the world's largest earthquakes?

The Ring of Fire hosts most of the world's biggest earthquakes, which is why Japan and Alaska, both along it, are shaken so often.

In which country was the Burgess Shale, famous for soft-bodied Cambrian fossils, discovered in 1909?

Canada's Burgess Shale fossils went largely unstudied after Walcott until researchers began re-examining them in the 1960s.

Uluru, the giant monolith in the Northern Territory desert, is made of which rock?

Sandstone Uluru has been closed to climbers since October 2019, because it is sacred to the Aṉangu and climbing was not generally permitted under their law.

Obsidian, used since the Stone Age for razor-sharp blades, is what kind of material?

Volcanic glass forms when lava cools too quickly for crystals to grow, which is why obsidian breaks into such sharp edges.

Which volcanic rock is so full of gas bubbles that it floats, sometimes forming ocean rafts?

Pumice floats until water slowly seeps into its pores, which is why rafts of it can drift across the ocean after an eruption.

Marble is a metamorphic rock formed when heat and pressure recrystallise which sedimentary rock?

Limestone turns to marble as its calcite recrystallises, and impurities such as clay and iron oxides become marble's veins and swirls.

Which volcanic rock carries most mined diamonds up to the surface from deep in the mantle?

Kimberlite magma erupts rapidly from deep in the mantle, tearing off diamond-bearing rock on the way and leaving the pipes that miners dig.

Which organisms caused the Great Oxidation Event, when oxygen first built up in Earth's atmosphere?

Cyanobacteria released oxygen through photosynthesis and built up the oxygen-rich atmosphere that animals depend on today.

In caves, what name is given to the mineral formations that grow up from the floor where water drips?

Stalagmites rise where drips leave minerals on the floor, and one that meets a stalactite growing down from above forms a column.

The world's longest known cave system, over 400 miles surveyed, is in which US state?

Kentucky's Mammoth Cave became part of the world's longest known cave in 1972, when explorers connected it with the even longer Flint Ridge system.

Devils Tower, the first US national monument, rises above the plains of which state?

Wyoming's Devils Tower is split by hundreds of parallel cracks between its columns, which draw rock climbers from far and wide.

Where is most of Earth's fresh water stored?

Ice caps and glaciers hold over two-thirds of Earth's fresh water, so large-scale melting of the ice sheets could raise sea levels substantially.

Which ancient Greek wrote Peri Lithon (On Stones), among the earliest studies of Earth materials?

Theophrastus took over Aristotle's school, the Lyceum, and led it for more than three decades.

Which 16th-century scholar wrote De re metallica, a classic book on mining and minerals?

Georgius Agricola's De re metallica was translated into English by Herbert Hoover, the mining engineer who later became US president, and his wife Lou.

Abraham Werner's followers held that Earth's rocks formed in what way?

From a vast ocean, Werner taught, the rocks had settled, but his theory met opposition even in his lifetime and was later discarded.

Which fossilised tree resin sometimes holds insects trapped inside it for millions of years?

Amber starts as sticky resin oozing from trees, which traps insects and bits of plants before it hardens.

Which mountain's summit is made of rock that formed on an ancient sea floor, complete with marine fossils?

Mount Everest is capped by rock laid down in a shallow sea more than 440 million years ago, then pushed nearly nine kilometres into the sky. It still holds tiny fragments of sea lilies.

Mount Rushmore's presidents and Yosemite's El Capitan are both made of which hard, coarse-grained rock?

Granite forms when molten rock cools slowly deep underground, giving its crystals time to grow big enough to see. Its name comes from the Latin granum, meaning grain.

Which volcano, measured from its base on the ocean floor, is sometimes called the tallest mountain in the world?

Mauna Kea rises about 10,000 metres from the sea bed, though less than half of that shows above the waves. Astronomers prize its dry, clear summit for telescopes.

Which brass-yellow mineral earned the nickname fool's gold for its resemblance to the precious metal?

Pyrite takes its name from the Greek for fire, because it throws sparks when struck against steel. Ötzi the Iceman carried some in his fire-lighting kit 5,000 years ago.

In which California national park do 'sailing stones' slide across a dry lakebed, pushed by wind and thin ice?

Death Valley's Racetrack Playa kept the mystery alive until 2014, when cameras finally caught rocks gliding as wind drove thin sheets of melting ice against them.

Which naturalist, famed for a theory about living things, explained how atolls grow on sinking volcanoes?

Charles Darwin published the idea in 1842, long before his book on evolution: as a volcanic island sinks, its fringing reef keeps growing upward until only a ring is left.

Which fuel, formed from the buried remains of swamp forests, gave the Carboniferous period its name?

Coal seams are the squashed remains of vast tropical swamp forests, and Carboniferous simply means coal-bearing. Deep burial slowly cooked the soggy plant matter into rock.

Old Faithful is the best-known example of which rare feature that shoots out boiling water and steam?

A geyser needs water, heat and a tight natural plumbing system that traps pressure until it bursts. So few places qualify that Yellowstone holds more than half of them.

In which present-day country is the Kola Superdeep Borehole, the deepest hole humans have ever drilled?

Russia's Kola Peninsula holds the hole, which Soviet scientists pushed 12,262 metres down. It is only 23 centimetres wide, and rock as hot as 180 °C helped end the drilling.

Which hard, glassy mineral is the main ingredient of most beach sand and keeps time inside modern watches?

Quartz is so hard and chemically stubborn that its grains outlast other minerals, which is why sand is full of it. A sliver vibrates at a steady beat when electrified, pacing a watch.

Which type of rock forms when molten material cools and hardens, above or below ground?

Igneous comes from the Latin for fiery. The family covers both lava that froze quickly at the surface and coarse-crystalled rock that set slowly deep underground.

What do geologists call molten rock while it is still underground, before it erupts as lava?

Magma takes its name from a Greek word for a thick ointment. It need not be fully liquid, either: geologists count semi-molten rock as magma too.

Which instrument, whose ancient forerunner was a Chinese bronze urn ringed with dragons, records earthquake shaking?

A seismograph traces ground motion as wavy lines. In AD 132 Zhang Heng's urn did it more simply: a dragon's mouth dropped a ball into a bronze toad below to signal a quake.

What name is given to the point on Earth's surface directly above the place where an earthquake begins?

The epicenter sits above the buried break itself, which is called the focus or hypocenter. Before instruments, people simply took it to be wherever the damage was worst.

Which metal is the most abundant element in the whole Earth by mass and makes up most of Earth's core?

Iron sank to the centre while the young Earth was hot enough to flow, dragging nickel down with it. Geologists call that great sinking the iron catastrophe.

Which steep-sided sea inlets, common along Norway's coast, were gouged out by moving ice and later flooded?

Fjords are often deeper than the open sea beside them. Norway's Sognefjord plunges about 1,300 metres, far below the shallow sill at its mouth.

Which mountain range, the longest on land, is rising as the Nazca Plate slides beneath a continent's edge?

The Andes run the whole length of South America. The sinking ocean plate that lifts them also sets off the earthquakes and eruptions along the range.

Which sudden ground collapse, notorious in central Florida, happens when water dissolves the rock below?

A sinkhole that opened in Winter Park, Florida, in 1981 swallowed five Porsches, a pickup truck and the deep end of the town's swimming pool. It struck during record-low groundwater levels.

Which US city was more than 80% destroyed in April 1906 by an earthquake and the fires that followed?

San Francisco shook as the San Andreas Fault ripped open along 296 miles. The fires that followed then burned for four days and nights.

Which fine-grained rock splits into the thin, flat sheets long used for roof tiles and school blackboards?

Slate begins as soft mud rock; heat and pressure line up its flaky minerals so that it splits cleanly. Its smooth sheets also became the beds of billiard tables.

Which element, second most abundant in Earth's crust, forms the backbone of most rocks and of computer chips?

Silicon makes up about 28% of the crust by mass, locked into the silicate minerals that form more than 90% of it. Only oxygen is more plentiful there.

Which lake, the deepest and oldest on Earth, fills a rift where a continent is slowly pulling apart?

Baikal sits in a Siberian rift that widens by about 4 mm a year. Its basin is at least 25 million years old and holds over a fifth of the world's fresh surface water.

The La Brea Tar Pits, whose sticky asphalt trapped sabre-toothed cats and mammoths, lie inside which US city?

Los Angeles surrounds the pits, where crude oil has seeped up through the ground for tens of thousands of years. Since 'la brea' is Spanish for the tar, the name says it twice.

Which hard rock, found as nodules in chalk, did Stone Age people chip into sharp blades, axes and arrowheads?

Flint breaks into thin splinters with razor-sharp edges, ideal for knife blades and scrapers. It later found a second career starting fires and firing muskets.

Which crescent-shaped lake is left behind when a river cuts through the neck of one of its own looping bends?

An oxbow lake has no current running through it, so silt slowly fills it in. Given time it turns into a swamp and then dries out altogether.

Which European capital was almost wiped out on All Saints' Day 1755 by an earthquake, a tsunami and fires?

Lisbon's ruin was the first earthquake studied scientifically for its effects over a wide area, which is why the disaster is counted as the birth of modern seismology.

Which mineral, the natural form of table salt, grows as cube-shaped crystals in thick underground beds?

Halite takes its name from the Greek word for salt. Buried beds of it can be squeezed upward through heavier rock, forming the salt domes that trap oil and gas.

Which extinct sea arthropods, hugely successful early animals, survived for almost 270 million years?

Trilobites left more than 22,000 described species in the fossil record. The last few vanished about 252 million years ago, in the worst mass extinction the oceans have known.

Mount Rainier and Mount Fuji are both which steep-sided type of volcano, known for explosive eruptions?

A stratovolcano is built from alternating layers of hardened lava and ash. Its lava is too sticky to flow far or to let gas escape easily, so pressure builds until it bursts.

Which term names Earth's rigid outer shell, the layer that is broken into slowly moving tectonic plates?

The lithosphere rides on the asthenosphere, a hotter, weaker layer that can slowly flow beneath it. Its name comes from the Greek for rocky sphere.

Which element's slow radioactive decay into lead lets geologists date rocks more than four billion years old?

Uranium atoms locked in a crystal turn steadily into lead, so the ratio of the two works as a clock. Carbon dating, by contrast, runs out after about 50,000 years.

Which era, spanning the Triassic, Jurassic and Cretaceous periods, is known as the Age of Dinosaurs?

Mesozoic literally means middle life. The era ran from about 252 to 66 million years ago, and both its start and its finish were marked by mass extinctions.

Which geological period ended with the Great Dying, the most severe mass extinction in Earth's history?

The Permian closed with about 81% of marine species wiped out. The leading suspect is a colossal outpouring of lava in Siberia that overheated the planet and soured the seas.

Which Indonesian volcano's 1815 eruption, the most powerful on record, caused the 'Year Without a Summer'?

Tambora blew apart in April 1815 with blasts heard more than 1,200 km away. Its haze of ash and sulfur gas cooled the whole planet, and harvests failed in many parts of the world the following year.

Which fast-moving current of hot gas and ash wiped out the town of Saint-Pierre, Martinique, in 1902?

A pyroclastic flow hugs the ground and moves far too fast to outrun. Of about 28,000 people in Saint-Pierre, one of the few survivors was a prisoner in a windowless cell.

Which seismic signals travel fastest through the Earth and so reach a recording station first after an earthquake?

P waves squeeze and stretch the ground much as sound does, so they pass through liquids as well as solids. Early-warning systems use their head start to raise the alarm.

Which earthquake scale, running from I to XII, rates a quake by its observed effects rather than its energy?

The Mercalli scale grades what people felt and what was damaged at each place. So one earthquake has a single magnitude but many intensities, depending on where you stood.

Which mineral test checks the colour of the powder left when a sample is dragged across unglazed porcelain?

Streak is more reliable than surface colour, which can vary a lot within a single mineral. The powder trail stays much the same, so geologists carry a small porcelain tile.

What do geologists call an underground layer of rock, sand or gravel that holds groundwater and feeds wells?

An aquifer takes its name from the Latin for water-bearing. One of the largest, the Ogallala, lies beneath parts of eight US states.

Which landscape of caves and vanishing streams takes its name from a plateau shared by Slovenia and Italy?

Karst forms where water dissolves soluble rock, so rivers and lakes are scarce and the drainage runs underground. The word reached European scholars in 1689, in an account of rivers that flow underground.

Which Victorian physicist underestimated Earth's age by calculating how fast a molten globe would cool?

Lord Kelvin's 1862 estimate of 20 to 400 million years left out two things: heat from radioactive decay, then undiscovered, and the slow churning of Earth's interior.

Mexico's Cave of the Crystals holds giant crystals, among the largest ever found, of which soft mineral?

Gypsum grew there extremely slowly, over at least 500,000 years, in a flooded chamber; the largest crystal is 11.4 metres long. Drained, the cave reaches a stifling 58 °C.

Ruby and sapphire are both gem varieties of which very hard mineral, also ground up as the abrasive emery?

Corundum is aluminium oxide, hard enough to scratch almost every other mineral. A trace of chromium makes it a red ruby, while other metals give sapphire its range of colours.

Which ancient southern landmass once joined Africa, South America and Antarctica before breaking apart?

Gondwana's fragments now make up about two-thirds of the world's continental area. Its name, meaning forest of the Gonds, was chosen by the Austrian scientist Eduard Suess.

Which English canal surveyor, nicknamed 'Strata', made the first detailed geological map of a whole country?

William Smith was overlooked by fellow scientists when his map appeared, and he ended up in debtors' prison. Recognition as the father of English geology came only late in his life.

Which Mexican volcano burst out of a farmer's cornfield in 1943 and built a cone over 400 metres high?

Parícutin gave scientists their first chance to record a volcano's entire life, from its birth in Dionisio Pulido's field to the end of its eruption nine years later.

Which layered mounds, built by microbes and still forming in Shark Bay, record some of Earth's earliest life?

Stromatolites grow as sticky mats of microbes trap grains of sediment, layer upon layer. They were at their peak about 1.25 billion years ago, long before any animals existed.

Which naturalist, later a Harvard professor, argued in 1837 that vast ice sheets had once smothered Europe?

Louis Agassiz combed the Alps for traces of vanished ice to back the theory, which he had worked out with the botanist Karl Schimper over the winter of 1836–37.

Which Irish archbishop famously calculated from the Bible that the world was created in October 4004 BC?

James Ussher even named the day, 23 October. Kepler and Newton, doing similar sums from scripture, arrived at creation dates within a dozen years of his.

Which hollow, crystal-lined rock often begins as a gas bubble in lava that minerals later coat from the inside?

A geode grows as mineral-rich groundwater slowly feeds the crystals lining its hollow. Trace elements in that water decide the colours hidden inside.