This earth science trivia quiz has 50 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 50 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
The mantle is by far the thickest layer at about 2,890 km, and the outer core is liquid while the inner core is solid.
Q 02Which Danish seismologist discovered in 1936 that Earth has a solid inner core?
Inge Lehmann
The inner core is a ball of mostly iron and nickel about 1,220 km in radius, sitting inside a liquid outer core about 2,260 km thick.
Q 03The boundary between Earth's crust and mantle is named after which scientist?
Mohorovičić
The 'Moho' is spotted by a jump in seismic wave speeds; oceanic crust above it is only 5 to 10 km thick.
Q 04What is Earth's mean radius, to the nearest kilometre?
6,371 km
Its average density of 5.515 grams per cubic centimetre makes it the densest planet in the solar system.
Q 05Which German meteorologist proposed the theory of continental drift in 1912?
Alfred Wegener
He noticed the coastlines of Africa and South America fitted like puzzle pieces; the idea was ridiculed and he died on a Greenland expedition in 1930, decades before it was vindicated.
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
The count depends on how you define them, and there are many minor plates besides; the fastest move about 160 mm a year, roughly the rate hair grows.
Q 08At which type of plate boundary do plates slide horizontally past each other?
Transform
Divergent boundaries build new ocean crust at mid-ocean ridges; convergent ones create subduction zones and mountains.
Q 09What is the volcanic and earthquake belt around the edge of the Pacific nicknamed?
The Ring of Fire
It follows the subduction zones where oceanic plates dive beneath their neighbours.
Q 10Which American cartographer discovered the rift valley running down the Mid-Atlantic Ridge?
Marie Tharp
Heezen initially dismissed her finding as 'girl talk'; the Library of Congress later named her one of the four greatest cartographers of the 20th century.
Q 11Nitrogen makes up about 78 percent of dry air. Roughly what share is the second most abundant gas?
21%
That gas is oxygen; argon is next at 0.93 percent, and 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
It is also the coldest layer of the atmosphere; 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 wrote about rotating machinery in 1835; the effect is far too weak to decide which way your bath drains.
Q 22In the Northern Hemisphere, low-pressure systems such as hurricanes rotate in which direction?
Counterclockwise
South of the equator it is the reverse, which is why Australian cyclones spin clockwise.
Q 23Jet streams generally flow in which direction?
West to east
Japanese meteorologist Wasaburo Oishi tracked them with balloons in the 1920s, and speeds of 400 km/h have been measured.
Q 14The Kármán line, the conventional boundary between the atmosphere and space, is at what altitude?
100 km
About 75 percent of the atmosphere's 5.15 quintillion kilograms sits in the troposphere, the bottom 6 to 20 km.
Q 15What is the age of the Earth, according to scientific consensus?
4.54 billion years
Clair Patterson pinned it down in 1956 using lead isotopes in the Canyon Diablo meteorite; Lord Kelvin had guessed as little as 20 million years.
Q 16Which is the largest division of geologic time?
Eon
There are four: Hadean, Archean, Proterozoic and Phanerozoic, and eras, periods, epochs and ages nest inside them.
Q 17The Phanerozoic eon began about 539 million years ago with which period?
Cambrian
Its three eras are the Paleozoic, Mesozoic and Cenozoic, names that mean ancient, middle and recent life.
Q 18Which geologic epoch began about 11,700 years ago, after the last ice age?
Holocene
It belongs to the Quaternary period; the International Commission on Stratigraphy keeps the official chart.
Q 19The extinction that wiped out the non-avian dinosaurs happened roughly how many million years ago?
66
It marks the boundary between the Cretaceous and Paleogene periods; the earlier Permian extinction was even deadlier.
Q 20Carbon-14, used to date organic remains, has a half-life of about how many years?
5,730
That limits it to samples under roughly 60,000 years old; uranium-lead dating handles rocks billions of years old.
Q 24Which English amateur meteorologist introduced the cloud names cirrus, cumulus, stratus and nimbus in 1802?
Luke Howard
The modern International Cloud Atlas recognises ten genera in the troposphere; fog is just stratus at ground level.
Q 25Which cloud type produces thunderstorms and can tower all the way to the tropopause?
Cumulonimbus
They are the largest free-convective clouds and bring lightning, hail and heavy rain.
Q 26El Niño got its name because Peruvian sailors noticed the warming around which time of year?
Christmas
The name means 'the boy', a reference to the Christ child; the cool phase, La Niña, is 'the girl'. Events come every two to seven years.
Q 27Earth's axis is tilted by about how many degrees, the tilt that gives us seasons?
23.4
It wobbles between about 22.1 and 24.5 degrees over a 41,000-year cycle, and the Moon helps keep it stable; Uranus is tipped over at 98 degrees.
Q 28Which Alexandria librarian first calculated Earth's circumference using shadows at Syene and Alexandria?
Eratosthenes
His answer of about 250,000 stadia works out remarkably close to the real 40,075 km, and he coined the word 'geography'.
Q 29Earth's magnetic field is generated by convection of molten iron and nickel in which layer?
The outer core
The process is called the geodynamo, and the field it makes is far weaker than a fridge magnet, at 25 to 65 microtesla.
Q 30The magnetic north pole has been drifting from northern Canada toward which region?
Siberia
It sat at Cape Adelaide on the Boothia Peninsula when first reached in 1831 and was 600 km from Resolute Bay by 2001.