Geologic Time Scale
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50 free Geologic Time Scale trivia questions with answers — science & nature quiz, new questions added Oct 2026.
The geologic time scale is Earth's calendar, and it is written in rock. Every layer of stone, every fossil and every boundary between them marks a chapter in a story so long that all of recorded human history fits into its last sliver. Learning the names on the chart is the quickest way to make sense of that story. This quiz covers the whole chart. It asks about the eras, periods and epochs and where their odd names come from, the mass extinctions and bursts of new life that divide them, and the famous fossils and rock formations that record them. It also covers the people who first learned to read the rocks and the methods geologists use to put an age on them. The questions start at a middle school level and climb to a few stretch questions for geology students, and every answer comes with a short explanation. Use it to revise for an earth science test, as a classroom warm-up, or as a ready-made round for quiz night.
30 of 50 questions with answers and explanations. Play the quiz
Q 01Which dinosaur died out so long before Tyrannosaurus rex that T. rex lived closer in time to humans?
Stegosaurus
Stegosaurus vanished about 145 million years ago, some 76 million years before T. rex appeared. Only 66 million years separate the last T. rex from us.
Q 02Which geologic period takes its name from a mountain range on the border of France and Switzerland?
Jurassic
Jurassic rocks were first picked out in the limestone of the Jura Mountains, just north of the Alps. Alexander von Humboldt studied them on a tour of the region in 1795.
Q 03Which geologic period, the last of the dinosaur age, takes its name from the Latin word for chalk?
Cretaceous
Cretaceous comes from creta, Latin for chalk, which built up on sea floors from the shells of tiny plankton. The White Cliffs of Dover are made of it.
Q 04Which geologic period ended with the 'Great Dying', the worst mass extinction in Earth's history?
Permian
The Permian closed with about 81% of marine species wiped out. It was also the greatest known mass extinction of insects.
Q 05Which crater, buried beneath Mexico's Yucatán Peninsula, marks the asteroid strike that wiped out the dinosaurs?
Chicxulub
Chicxulub was found in the late 1970s by geophysicists who were hunting for oil, not dinosaurs. The crater is about 200 km wide and lies under a kilometre of younger rock.
Q 06Which group of fish first appears in the fossil record about 450 million years ago, before trees even existed?
Sharks
Sharks left their oldest known traces, a few fossil scales, some 450 million years ago. They have since come through five mass extinctions.
Q 07Which proposed epoch of geologic time did geologists vote down in 2024?
Anthropocene
The Anthropocene was voted down after 15 years of debate, largely because its proposed start was so recent. Mud in Canada's Crawford Lake had been picked as its marker.
Q 08Which sail-backed predator, often mistaken for a dinosaur, died out 40 million years before dinosaurs appeared?
Dimetrodon
Dimetrodon is more closely related to mammals than to any dinosaur. Its famous sail was held up by long spines growing out of its backbone.
Q 09About how old is Earth, an age worked out from meteorites that formed alongside the planets?
4.5 billion years
At about 4.5 billion years, Earth is roughly a third as old as the universe. The figure comes from meteorites, leftovers from the birth of the Solar System.
Q 10Which supercontinent, formed about 335 million years ago, began to break apart while dinosaurs roamed it?
Pangaea
Pangaea joins the Greek words for 'all' and 'Earth'. Alfred Wegener used the name in 1920 while arguing that the continents had once been a single landmass.
Q 11Which is the largest unit of the geologic time scale, with just four covering all of Earth's history?
Eon
An eon is the top rung of the ladder: eons split into eras, eras into periods, and periods into epochs. The longest of the four lasted almost two billion years.
Q 12Which era, nicknamed the Age of Reptiles, covers the whole reign of the non-avian dinosaurs?
Mesozoic
Mesozoic means 'middle life', a name proposed in 1840 by the geologist John Phillips. The 'Age of Reptiles' tag came from the paleontologist Gideon Mantell.
Q 13Which span of geologic time, nicknamed the Age of Mammals, covers the 66 million years since the dinosaurs' extinction?
Cenozoic
The Cenozoic saw mammals take over the land once the dinosaurs were gone, growing from mostly small animals into the largest on land. Its name means 'new life'.
Q 21Which principle, first proposed in 1669, states that in undisturbed rock layers the oldest lie at the bottom?
Superposition
Superposition gives only the order in which layers formed, never an age in years. It also fails where folding has tipped a stack of rock past the vertical.
Q 22Which Danish anatomist, later a Catholic bishop, argued that 'tongue stones' found in rocks were really ancient teeth?
Nicolas Steno
Nicolas Steno is counted among the founders of modern geology, yet in 1675 he became a priest. Pope John Paul II beatified him in 1988.
Q 23Which Scottish 'father of modern geology' wrote that Earth showed 'no vestige of a beginning, no prospect of an end'?
James Hutton
Q 14Which epoch, popularly called the Ice Age, ended about 11,700 years ago as the great ice sheets retreated?
Pleistocene
The Pleistocene was not one long freeze: its ice sheets advanced and melted back again and again, at intervals of roughly 40,000 to 100,000 years.
Q 15Which epoch began as the last glacial period ended and takes in all of written human history?
Holocene
The Holocene takes its name from Greek words meaning 'wholly new'. It is a warm spell between advances of the ice rather than the end of the ice ages.
Q 16Which geologic period began about 2.6 million years ago and runs through the ice ages to the present day?
Quaternary
The Quaternary covers roughly the whole time that recognisable humans have existed. Its name was coined in 1829 for young sediments in France's Seine Basin.
Q 17Which period, named after a Latin name for Wales, saw most major animal groups appear in a sudden burst?
Cambrian
The Cambrian explosion lasted between 13 and 25 million years, a blink in geologic terms. Almost all modern animal phyla first show up in its rocks.
Q 18Which period is nicknamed the Age of Fishes, when armoured giants such as Dunkleosteus hunted the seas?
Devonian
The Devonian is called the Age of Fishes, but it changed the land too: the first forests took root late in the period. Dunkleosteus was one of its armoured placoderms.
Q 19Which period of swamp forests was home to Meganeura, a dragonfly relative with a wingspan of about 70 cm?
Carboniferous
The Carboniferous means 'coal-bearing': its swamp forests became coal beds found around the world. Meganeura fossils first turned up in a French coal field in 1880.
Q 20Which period saw the first dinosaurs and the first mammals appear as life recovered from the 'Great Dying'?
Triassic
The Triassic is named after a stack of three distinct rock layers that crops up across southern Germany. Friedrich Alberti coined the name in 1834.
James Hutton took the tilted rocks of Siccar Point as proof that land is worn down and rebuilt in endless cycles. He also inherited two family farms and set about improving them.
Q 24Which principle, summed up as 'the present is the key to the past', says ancient rocks formed by processes seen today?
Uniformitarianism
Uniformitarianism got its name from William Whewell, the scholar who also coined the word 'scientist'. Its rival, catastrophism, put the past down to sudden upheavals.
Q 25Which geologist wrote Principles of Geology, which a young Darwin took with him aboard HMS Beagle?
Charles Lyell
Charles Lyell argued that small changes pile up over enormous spans of time. Darwin was handed the first volume by the Beagle's captain, Robert FitzRoy, just before sailing.
Q 26Which English surveyor, nicknamed 'Strata', published the first detailed geological map of an entire country in 1815?
William Smith
William Smith saw in coal pits and canal excavations that rock layers always sit in the same order. Later ruined financially, he spent time in a debtors' prison.
Q 27Which technique, pioneered by Rutherford and Boltwood, dates rocks in years from the decay of unstable isotopes?
Radiometric dating
Radiometric dating works like an hourglass: unstable atoms turn into stable ones at a fixed rate, so the ratio of the two shows how much time has passed.
Q 28Which property of a radioactive isotope is about 5,700 years for carbon-14 and 700 million years for uranium-235?
Half-life
Half-life began as 'half-life period', a term that dates to Ernest Rutherford's work in 1907. It is the time it takes for half of a radioactive sample to decay.
Q 29Which Victorian physicist calculated from Earth's rate of cooling that it was only 20 to 400 million years old?
Lord Kelvin
Lord Kelvin later cut his estimate to between 20 and 40 million years. Darwin, who died before that final cut, had already said Kelvin's figures left too little time for evolution.
Q 30Which Irish archbishop worked out from the Bible that the world was created in 4004 BC?
James Ussher
James Ussher even named the day: 23 October. His date was no outlier, since the astronomer Johannes Kepler had put creation at 3992 BC.