A World Tour
Geo-Quest Heroes
The ground under your feet is moving, the top of Mount Everest was once under the sea, and the deepest hole ever dug barely scratched our planet's surface. Let's dig in!
Did you know?
Earth's outer shell is broken into giant pieces called plates. Under the Atlantic Ocean, two plates move apart just 1 to 4 cm a year, about as fast as your fingernails grow! Slowly, this moves whole continents.
The top of Mount Everest is made of limestone that formed under an ancient sea! Scientists have found tiny bits of fossils in it, such as trilobites (extinct sea animals with hard shells).
The deepest hole ever dug by people is the Kola Superdeep Borehole in Russia, 12,262 metres deep. It is only 23 cm wide, and it reached just a third of the way through the crust there!
Try this: Scratch Test Like a Geologist
Collect five different small stones or pebbles. Try to scratch each one with your fingernail, then with a coin. Which ones get a mark, and which stay smooth? Line them up from softest to hardest. Geologists use the Mohs scale, created by Friedrich Mohs in 1812. It goes from talc (1, the softest) to diamond (10, the hardest).
Go further: Listening to Earth's Insides
Nobody can dig to the centre of the Earth, so how do we know what is there? Scientists study earthquake waves. These waves travel through the planet and bend, bounce or change speed as they pass through different layers. From such clues, we know that Earth's inner core is a solid ball of metal with a radius of about 1,220 km, about 70% of the Moon's. Its surface is about 5,400 °C, roughly as hot as the surface of the Sun!