Earth Science
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7correct to beat the crowd
This earth science trivia quiz has 100 free questions with answers and goes from the inner core to the edge of space: the planet's layers and who found them, plate tectonics and the ridiculed meteorologist who proposed it, the layers and gases of the atmosphere, the four eons and the epoch we live in, how radiometric dating gives Earth an age of 4.54 billion years, the Coriolis effect and jet streams, cloud names, El Niño, the wandering magnetic pole and geomagnetic reversals, the aurora, axial tilt and the seasons, ice ages, the deepest point in the ocean and the woman who mapped the Atlantic floor. It is written for middle and high school science students, teachers building a review round, pub quizzers and anyone curious about the planet under their feet. Easy questions cover what most people remember from school; the hard ones ask for percentages, dates and the names of the discoverers. Every answer has been checked against a reliable source and each question shows its citation once you have answered.
30 of 100 questions with answers and explanations. Play the quiz
Q 01Which is the correct order of Earth's layers from the surface inward?
Crust, mantle, outer core, inner core
From the surface inward the order is crust, mantle, outer core, inner core; the mantle is the thickest layer at about 2,890 km, and the liquid outer core surrounds the solid inner core.
Q 02Which Danish seismologist discovered in 1936 that Earth has a solid inner core?
Inge Lehmann
Inge Lehmann, a seismologist at the Danish Geodetic Institute, showed in 1936 that P-waves reflecting off a boundary inside the core mean Earth has a solid inner core within the liquid outer core.
Q 03The boundary between Earth's crust and mantle is named after which scientist?
Mohorovičić
Croatian seismologist Andrija Mohorovičić identified the crust–mantle boundary in 1909 from a jump in seismic wave speeds; the 'Moho' lies only 5 to 10 km beneath the ocean floor.
Q 04What is Earth's mean radius, to the nearest kilometre?
6,371 km
Earth's mean radius is 6,371 km; the equatorial radius is slightly larger at 6,378 km and the polar radius smaller at 6,357 km, because rotation flattens the planet at the poles.
Q 05Which German meteorologist proposed the theory of continental drift in 1912?
Alfred Wegener
Alfred Wegener presented continental drift in 1912, noting how the coastlines of Africa and South America fit together; he died on a Greenland expedition in 1930, decades before the theory was accepted.
Q 06What name is given to the supercontinent that Wegener argued once joined all the continents together?
Pangaea
Wegener himself called it 'Urkontinent'; the theory was only accepted after seafloor spreading was confirmed in the 1960s.
Q 07How many major tectonic plates does Earth's lithosphere have?
Seven or eight
Most classifications count seven or eight major plates — African, Antarctic, Eurasian, North American, Pacific, South American and Indo-Australian, sometimes split into Indian and Australian — plus dozens of minor plates.
Q 08At which type of plate boundary do plates slide horizontally past each other?
Transform
At a transform boundary plates slide horizontally past each other, as along California's San Andreas Fault; divergent boundaries build new crust at mid-ocean ridges and convergent ones create subduction zones.
Q 09What is the volcanic and earthquake belt around the edge of the Pacific nicknamed?
The Ring of Fire
The Ring of Fire is a roughly 40,000 km horseshoe of subduction zones around the Pacific, where oceanic plates dive beneath their neighbours, hosting most of the world's active volcanoes.
Q 10Which American cartographer discovered the rift valley running down the Mid-Atlantic Ridge?
Marie Tharp
Marie Tharp, plotting sonar soundings with Bruce Heezen in 1952, found a continuous rift valley along the Mid-Atlantic Ridge; Heezen first dismissed it as 'girl talk' before the evidence won him over.
Q 11Roughly what share of dry air is made up of the second most abundant gas?
21%
The second most abundant gas makes up about 21% of dry air, behind nitrogen's 78 percent; carbon dioxide is only about 0.04 percent.
Q 12The ozone layer that absorbs ultraviolet light sits in which layer of the atmosphere?
Stratosphere
Because ozone absorbs UV, temperature actually rises with height in the stratosphere, the opposite of the troposphere below it.
Q 13In which atmospheric layer do most meteors burn up?
Mesosphere
Most meteors burn up in the mesosphere, 50 to 85 km up, where the air is just dense enough to vaporise them; it is also the coldest layer, and the International Space Station orbits above it in the thermosphere.
Q 21The Coriolis effect, which shapes weather systems, is named after a scientist of which nationality?
French
Gaspard-Gustave de Coriolis was a French mathematician and engineer who described the deflecting force in an 1835 paper on rotating machinery; the effect is far too weak to decide which way a bath drains.
Q 22In the Northern Hemisphere, low-pressure systems such as hurricanes rotate in which direction?
Counterclockwise
Northern Hemisphere lows such as hurricanes spin counterclockwise because the Coriolis effect deflects inflowing air to the right; south of the equator the reverse applies, so Australian cyclones spin clockwise.
Q 23Jet streams generally flow in which direction?
West to east
Q 14The Kármán line, the conventional boundary between the atmosphere and space, is at what altitude?
100 km
The Kármán line is set at 100 km above sea level, the altitude the FAI adopted as the edge of space because aerodynamic lift becomes negligible there; it is named for engineer Theodore von Kármán.
Q 15What is the age of the Earth, according to scientific consensus?
4.54 billion years
Earth is about 4.54 billion years old; Clair Patterson pinned the figure down in 1956 using lead isotopes from the Canyon Diablo meteorite, after Lord Kelvin had guessed as little as 20 million years.
Q 16Which is the largest division of geologic time?
Eon
The eon is the largest formal division: there are four — Hadean, Archean, Proterozoic and Phanerozoic — with eras, periods, epochs and ages nesting inside them.
Q 17The Phanerozoic eon began about 539 million years ago with which period?
Cambrian
The Cambrian, named by Adam Sedgwick after Cambria, the Latin name for Wales, opened the Phanerozoic and its Paleozoic era; the eon's three eras are the Paleozoic, Mesozoic and Cenozoic.
Q 18Which geologic epoch began about 11,700 years ago, after the last ice age?
Holocene
The Holocene began about 11,700 years ago as the last glacial period ended; it sits in the Quaternary period, and its base is formally defined in a Greenland ice core.
Q 19The extinction that wiped out the non-avian dinosaurs happened roughly how many million years ago?
66
The impact-driven extinction 66 million years ago marks the Cretaceous–Paleogene boundary; the end-Permian extinction about 252 million years ago was even deadlier.
Q 20Carbon-14, used to date organic remains, has a half-life of about how many years?
5,730
Carbon-14's half-life of about 5,730 years limits the method to samples under roughly 50,000 to 60,000 years old; uranium-lead dating handles rocks billions of years old.
Jet streams flow from west to east because Earth's rotation deflects poleward-moving air; Japanese meteorologist Wasaburo Oishi tracked them with balloons in the 1920s, and speeds near 400 km/h have been recorded.
Q 24Which English amateur meteorologist introduced the cloud names cirrus, cumulus, stratus and nimbus in 1802?
Luke Howard
Luke Howard, a London pharmacist, proposed the Latin names cirrus, cumulus, stratus and nimbus in his 1802 essay on cloud modifications; the International Cloud Atlas recognises ten genera in the troposphere.
Q 25Which cloud type produces thunderstorms and can tower all the way to the tropopause?
Cumulonimbus
Cumulonimbus clouds are the towering storm clouds whose anvil tops can reach the tropopause; they bring lightning, hail and heavy rain.
Q 26El Niño got its name because Peruvian sailors noticed the warming around which time of year?
Christmas
Peruvian fishermen noticed the warm current arriving around Christmas, so they called it El Niño, 'the boy', for the Christ child; its cool counterpart La Niña is 'the girl'.
Q 27Earth's axis is tilted by about how many degrees, the tilt that gives us seasons?
23.4
Earth's axial tilt is about 23.4 degrees; it varies between roughly 22.1 and 24.5 degrees over a 41,000-year cycle, while Uranus is tipped over at about 98 degrees.
Q 28Which Alexandria librarian first calculated Earth's circumference using shadows at Syene and Alexandria?
Eratosthenes
Eratosthenes, chief librarian at Alexandria around 240 BC, compared the Sun's shadow angles at Syene and Alexandria to get about 250,000 stadia, remarkably close to the true 40,075 km; he also coined 'geography'.
Q 29Earth's magnetic field is generated by convection of molten iron and nickel in which layer?
The outer core
Convection of molten iron and nickel in the outer core drives the geodynamo; the field it produces is only 25 to 65 microtesla at the surface, weaker than a fridge magnet.
Q 30The magnetic north pole has been drifting from northern Canada toward which region?
Siberia
James Clark Ross first reached the pole in 1831 on Canada's Boothia Peninsula; in the 1990s its drift accelerated to roughly 50 km a year, carrying it across the Arctic Ocean toward Siberia.