49 Fun Facts About Geology

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

His angular unconformity at Siccar Point convinced visitors the Earth showed 'no vestige of a beginning, no prospect of an end'.

What did Alfred Wegener name the single ancient landmass in his 1912 continental drift theory?

He first called it the 'Urkontinent'; the Greek name means 'all land'. He died on a Greenland expedition in 1930, decades before his idea was accepted.

What was Alfred Wegener's field, which made geologists slow to accept continental drift?

He was a climatologist and meteorologist who made four Greenland expeditions; acceptance came only after seafloor spreading was confirmed in the 1960s.

What is the accepted age of the Earth, in billions of years?

Clair Patterson fixed it in 1956 by uranium-lead dating the Canyon Diablo meteorite, since Earth's own oldest rocks have been recycled.

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

They are older than any surviving rock; the oldest intact rocks, the Acasta Gneiss of Canada, are about 4.03 billion years old.

The Acasta Gneiss, the oldest known intact crustal rock, lies in which Canadian territory?

It sits about 300 km north of Yellowknife on the edge of the Slave Craton, mostly hidden under glacial deposits.

How many major tectonic plates is Earth's lithosphere usually said to be divided into?

Plus dozens of minor 'platelets'; the Nazca plate moves about 160 mm a year, roughly the speed hair grows.

What is the strongest driver of plate motion, according to modern geologists?

Cold, dense oceanic crust sinking into the mantle drags the rest of the plate along behind it.

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

The inner core is a mostly iron-nickel ball about 1,220 km in radius, hotter than the Sun's surface but solid under pressure.

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

It shows up as a jump in seismic wave speed; the crust above it is only 5 to 70 km thick.

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

Convection in the molten iron-nickel outer core acts as a dynamo; the inner core beneath it is solid.

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

It sits inside the Quaternary period, the Cenozoic era and the Phanerozoic eon.

Roughly what share of Earth's history is covered by the Precambrian, the time before complex life?

The Phanerozoic, with all its trilobites, dinosaurs and people, is only the last 12 percent.

Which of these is one of the four formally defined eons of Earth's history?

The four are Hadean, Archean, Proterozoic and Phanerozoic; the others listed are periods.

Nicolas Steno, who set out the law of superposition in 1669, realised "tongue stones" were actually what?

He dissected a shark's head in 1666; he later became a Catholic bishop and was beatified in 1988.

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

Darwin took volume one aboard the Beagle and later said it showed how 'incomprehensibly vast' past time had been.

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

The debris avalanche raced at up to 155 mph and the mountain lost about 1,300 feet of height; 57 people died.

The Chicxulub crater lies buried beneath which peninsula?

Pemex geophysicists found it in 1978; the worldwide iridium spike in boundary clay pointed to an impact.

Which asteroid-rich element was found concentrated in the clay layer marking the end of the Cretaceous?

The Alvarez team's discovery in 1980 preceded the identification of the crater itself.

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

Energy rises about 31.6-fold per step; seismologists now mostly use the moment magnitude scale instead.

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

The Great Chilean earthquake of 22 May 1960 sent tsunamis as far as Hawaii and Japan.

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

Diamond is 10, but the scale is ordinal: diamond is actually about four times harder than corundum at 9.

Which mineral group makes up about 60 percent of the Earth's crust?

The name comes from the German for 'field flake'; Apollo moon rocks and Curiosity's Martian samples are rich in it too.

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

Cooling lava contracted into mostly hexagonal columns 50 to 60 million years ago; UNESCO listed it in 1986.

Roughly how old, in billions of years, is the Vishnu Schist at the very bottom of the Grand Canyon?

The Vishnu Schist in the Inner Gorge sits below the 'Great Unconformity', a half-billion-year gap in the record.

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

New crust forms as the plates spread about 2.5 cm a year; Iceland is one of the few places the ridge rises above the sea.

Which cartographer's 1950s map revealed the Atlantic's rift valley, a find her partner first dismissed as 'girl talk'?

Working with Bruce Heezen, Tharp was barred from research ships; the Library of Congress later named her one of the century's four greatest cartographers.

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

It is a right-lateral strike-slip fault about 1,200 km long, named by Andrew Lawson in 1895; the 1906 quake ruptured 430 km of it.

Roughly how long ago was Yellowstone's last giant eruption, the Lava Creek event?

It threw out about 1,000 cubic kilometres of ash; the hotspot has left a trail of older calderas along the Snake River Plain.

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

The Hawaiian-Emperor chain runs 6,200 km with a mysterious 60-degree bend; the newest volcano, Kamaʻehuakanaloa, is still underwater.

The Himalayas still rise about 5 mm a year from the collision of the Eurasian Plate and which other?

Limestone laid down on the floor of the Tethys Sea now sits near the summit of Everest.

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

The Pacific Plate dives beneath the Mariana Plate; the Challenger Deep bottoms out around 10,935 metres, deeper than Everest is tall.

The 1883 eruption of Krakatoa produced the loudest sound in recorded history. Roughly how far away was it heard?

It reached Rodrigues near Mauritius; most of the 36,000 deaths came from tsunamis, and global temperatures fell about 0.4 °C.

What proportion of the world's earthquakes occur within the Pacific Ring of Fire?

The 40,000-km belt also holds around two-thirds of the world's active and dormant volcanoes.

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

Charles Walcott found it in Yoho National Park, British Columbia, and collected 65,000 specimens; Stephen Jay Gould's Wonderful Life made it famous.

Uluru, the monolith rising 348 metres from the Northern Territory desert, is made of which rock?

Its arkose sandstone is about 550 million years old and it rises 348 metres; climbing was banned in 2019 out of respect for the Anangu.

Obsidian, prized for blades sharper than steel scalpels, is what kind of material?

It forms when silica-rich lava cools too fast to crystallise; some surgeons have used obsidian blades, though the FDA has not approved them.

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

Its porosity is 64 to 85 percent; rafts can float for years, carrying marine life, before becoming waterlogged.

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

Its Greek name means 'shining stone'; the veins are impurities like clay and iron oxides redistributed during metamorphism.

Most natural diamonds formed 150 to 250 km down in the mantle. Which volcanic rock carries them to the surface?

They are one to 3.5 billion years old, and the eruptions that delivered them happened tens to hundreds of millions of years ago.

Which organisms caused the Great Oxidation Event about 2.4 billion years ago?

Oxygen was poison to the anaerobic life of the time; the biosphere may have shrunk by more than 80 percent.

Why did banded iron formations stop forming about 1.85 billion years ago?

Dissolved iron could no longer stay in seawater once oxygen was around to rust it out.

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

Mammoth Cave dissolved out of limestone; the deepest cave, Veryovkina in the Caucasus, drops more than 2,200 metres.

Devils Tower, the first US national monument, is a columned mass of which igneous rock?

The magma intruded about 40.5 million years ago; Theodore Roosevelt protected it in 1906 and Close Encounters made it a film star.

Roughly what fraction of Earth's land surface is covered by glaciers?

Together with the ice sheets they hold about 69 percent of the world's fresh water and carve U-shaped valleys as they go.

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

Pliny the Elder later catalogued the minerals and metals in practical use across the Roman world.

Which 16th-century author of De Natura Fossilium is seen as the founder of geology as a discipline?

His 1546 work predates Steno's law of superposition by more than a century.

Abraham Werner led the 'Neptunists', who believed all rocks had formed how?

Their rivals the Plutonists argued that some rocks were born of volcanic activity.

Who produced the first geological map of the United States, in 1809?

He crossed and recrossed the Alleghenies some 50 times, beating William Smith's map of England by six years.