Earth Science
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7correct to beat the crowd
This earth science trivia quiz has 98 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 98 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
Crust, mantle, outer core, inner core: nobody has drilled beyond the crust, so the deeper layers are mapped from the way earthquake waves speed up, slow down and bend on their way through the planet.
Q 02Which Danish seismologist discovered in 1936 that Earth has a solid inner core?
Inge Lehmann
Inge Lehmann noticed faint earthquake waves turning up in the 'shadow zone' behind the core, where none were expected, and reasoned that a solid inner core must be deflecting them.
Q 03The boundary between Earth's crust and mantle is named after which scientist?
Mohorovičić
Mohorovičić, a Croatian seismologist, spotted the boundary as a sudden jump in the speed of earthquake waves; the 'Moho' lies only about 7 km beneath the ocean floor but some 35 km under the continents.
Q 04Earth's rotation squashes the planet slightly out of round, flattening it where?
The poles
The poles: the spin flings the equator outward by about 21 km, so the summit of Ecuador's Chimborazo, not Everest, is the point on the surface farthest from Earth's centre.
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 06Which supercontinent held nearly all of Earth's land before it began to break apart in the age of the dinosaurs?
Pangaea
Pangaea began to split in the Jurassic, and the widening gaps between its pieces filled with water to become the Atlantic and Indian oceans.
Q 07Which US island chain formed as the Pacific Plate slid over a mantle hotspot?
Hawaiian Islands
The Hawaiian Islands lie in a line because the plate keeps creeping northwest over the hotspot: each island was carried off in turn, so Kauai is millions of years older than the Big Island.
Q 08At which type of plate boundary do plates slide horizontally past each other?
Transform
Transform boundaries neither create nor destroy crust: the plates just grind sideways, and along California's San Andreas Fault that slip is slowly carrying Los Angeles toward San Francisco.
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
100 km is the round figure the world air-sports federation uses for where the air becomes too thin for wings to work; the United States is more generous, awarding astronaut wings from 80 km.
Q 15What is the age of the Earth, according to scientific consensus?
4.54 billion years
4.54 billion years comes from a meteorite: Earth's own first rocks were recycled long ago, so in 1956 Clair Patterson dated lead from the Canyon Diablo meteorite, which formed along with the planets.
Q 16Which is the largest division of geologic time?
Eon
The eon is the biggest unit, and Earth has had only four; the first, the Hadean, is named after Hades, the Greek underworld, for the intense heat of the newborn planet.
Q 17The Phanerozoic began about 539 million years ago with which geological period?
Cambrian
The Cambrian opened with an 'explosion' of life: in a geologically brief burst, most of the major animal groups alive today made their appearance in the fossil record.
Q 18Which geologic epoch began about 11,700 years ago, after the last ice age?
Holocene
The Holocene is the warm spell since the last glacial period ended, and it has seen all of humanity's recorded history and the rise and fall of every civilisation.
Q 19The extinction that wiped out the non-avian dinosaurs happened roughly how many million years ago?
66
66 million years ago an asteroid at least 10 km wide struck what is now Mexico's Yucatán coast; the debris it threw up darkened the sky, photosynthesis stopped and food chains collapsed.
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 means too little is left to measure after roughly 50,000 years, so older rocks need slower clocks such as uranium decaying into lead.
Jet streams blow from west to east because Earth's spin deflects air heading for the poles; airlines ride them eastbound to save time and fuel, which is why flying east is usually quicker.
Q 24The cloud names cirrus and stratus, coined by the London chemist Luke Howard, come from which language?
Latin
Latin cirrus means 'a lock of hair' and stratus 'a spreading', so Howard's names simply describe what each cloud looks like: wispy curls and flat sheets.
Q 25Which cloud type produces thunderstorms and can tower all the way to the tropopause?
Cumulonimbus
Cumulonimbus tops flatten into an anvil because the rising air eventually meets air as warm as itself, loses its lift and can only spread out sideways.
Q 26El Niño got its name because Peruvian fishermen 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
At 23.4 degrees, the tilt also sets the tropics: the Sun can stand directly overhead only between 23.4 degrees north and south, the Tropics of Cancer and Capricorn.
Q 28Which chief librarian of Alexandria worked out Earth's circumference by comparing noon shadows in two Egyptian cities?
Eratosthenes
Eratosthenes heard that the midsummer noon Sun shone straight down a well at Syene, measured a shadow of one-fiftieth of a circle at Alexandria, and multiplied the distance between them by fifty.
Q 29Earth's magnetic field is generated by convection of molten iron and nickel in which layer?
The outer core
The outer core's churning liquid metal works like a dynamo, and the magnetic field it generates fends off the solar wind, which would otherwise strip away the upper atmosphere.
Q 30The magnetic north pole has been drifting from northern Canada toward which region?
Siberia
Siberia is where it is heading: by 2019 the drift had quickened to about 55 km a year, fast enough that the magnetic model behind navigation systems had to be updated ahead of schedule.