10cm
Earthworms
They eat soil and leave it behind as castings, plowing it soft. Charles Darwin studied earthworms for about 40 years.
Everything you meet going straight down from the ground in Japan, through the center of the Earth, to the surface in Brazil, from shallowest to deepest.
0–35 kmThe Crust
Earth's thin outer skin. If Earth were an apple, the crust would be about as thick as its peel.
22cm
Soil microbes
One teaspoon of soil (about 1 g) holds hundreds of millions to billions of microbes. They break down fallen leaves into food for plants.
35cm
Cicada nymphs
They spend several years underground, sipping sap from tree roots. Only their last few weeks are lived above ground as adults.
50cm
Moles
The small Japanese mole of eastern Japan's plains tunnels through park and garden soil even in big cities. Its front paws work like shovels.
~1m
Gas and water pipes
Just under the road run gas pipes, water mains, power lines and telecom cables. This is the layer that gets dug up during roadwork.
1.4m
Ant nests
An underground city of chambers linked by tunnels. Some species dig several meters deep.
2m
Tree roots
Most tree roots spread through the top 1–2 m of soil, because roots need oxygen as well as water.
3m
Land that used to be sea
Many of Japan's big cities stand on reclaimed sea and marshland. The Marunouchi side of Tokyo Station, for example, was an inlet of the sea called Hibiya-irie until the early Edo period (early 1600s).
5m
Sewers
Laid end to end, the sewer pipes of Tokyo's 23 wards would run about 16,000 km—roughly a round trip between Tokyo and Sydney.
8m
Subway
Tokyo’s Ginza Line, opened in 1927, was billed as “the first subway in the Orient.” It runs just below the street. The newer the line, the deeper it tends to go.
12m
Alluvium
Soft mud and sand laid down by rivers and the sea over roughly the last 10,000 years. It holds seashells from the Jomon period, when the sea reached far inland.
22m
Naumann's elephant fossil
Found in 1976 about 22 m below Nihonbashi-Hamacho, Tokyo, during subway construction. 120,000–150,000 years ago, elephants roamed Japan's plains.
28m
The layer that holds up skyscrapers
A hard gravel layer (the bearing stratum). Tall buildings drive piles down to layers like this to stand firm.
40m
Deep underground space
In Japan, ground deeper than 40 m (among other criteria) counts as “deep underground.” Approved public projects can generally use it without compensating the landowners above (under a 2001 law). The planned Chuo Shinkansen maglev line will run here.
42.3m
Roppongi Station (Oedo Line)
Platform 1 of Roppongi Station on Tokyo's Oedo Line is 42.3 m underground—the deepest subway station in Tokyo.
~50m
Tokyo Skytree's piles
The 634 m tower is anchored by wall-like piles (“knuckle walls”) that reach about 50 m down.
~50m
The Metropolitan Outer Floodway
About 50 m beneath Kasukabe, Saitama, runs one of the world’s largest underground floodwater channels. Its tank of giant pillars is nicknamed the “Underground Temple.”
~70m
Doai Station
On the JR Joetsu Line in Gunma, the down platform sits about 70 m below the station building. Reaching the exit takes 486 steps—Japan’s most famous “mole station.”
~120m
The world's deepest roots
A wild fig at Echo Caves in South Africa is said to have sent its roots about 120 m down (Guinness World Records).
≤300m
Kuro-yu, the black hot water
Dark, tea-colored water popular at Tokyo's public bathhouses. Most of it is pumped from wells shallower than 300 m. The color comes from humic acid, formed as ancient plants decayed.
333mTokyo Tower, upside down
634mTokyo Skytree, upside down
200–1,500m
Natural gas and iodine
In the Minami-Kanto gas field, centered on Chiba, natural gas is dissolved in groundwater 200–1,500 m down. That water is also rich in iodine: Japan produces about a third of the world's iodine.
~1,300m
The devil worm
A 0.5 mm nematode found about 1.3 km down in a South African gold mine (2011). Its scientific name comes from Mephisto, the devil of the Faust legend.
1,000–1,500m
Deep hot springs
The deeper you go, the warmer it gets. In Tokyo, water from 1,000 m is about 25°C, and from 1,500 m about 40°C. That's why hot springs flow even without volcanoes.
2,224m
The world's deepest cave
Krubera Cave in Georgia is about 2,224 m deep—the deepest natural pit people can descend on their own feet.
~2–3km
Bedrock
Under Japan’s plains, older and harder “basement rock” appears beneath the soft layers. Under Tokyo it lies about 2–3 km down.
2,800m
The bold traveler
In water 2.8 km down in a South African gold mine, scientists found a bacterium living entirely alone, the only species there. It feeds on substances made when radiation from uranium and other elements in the rock splits water. Its name, audaxviator, means “bold traveler,” from a line in Journey to the Center of the Earth.
3,776mMount Fuji, upside down
~4,000m
The world's deepest mine
South Africa's Mponeng gold mine reaches about 4 km below the surface. The rock is about 66°C, so ice is pumped in to cool the tunnels while miners dig for gold.
~4–5km
The temperature limit of life
The highest temperature at which life is known to multiply is 122°C (JAMSTEC, 2008). Under Japan, the ground nears that temperature at about 4–5 km.
to ~5km
The deep biosphere
Microbes have been found as deep as about 5 km beneath the continents. All the life underground is estimated to weigh, in carbon, about 250–400 times as much as all of humanity (2018).
7,906m
The drilling ship Chikyu
In 2024, off Miyagi, Japan, the Chikyu drilled to 7,906 m below the ship, a Guinness World Record for scientific drilling. It bored 980 m into the seafloor beneath 6,897.5 m of water.
8,849mMount Everest, upside down
~10,000mThe cruising altitude of a jetliner
12,262m
Kola Superdeep Borehole
The deepest hole humans have ever dug. The Soviet Union spent about 20 years drilling it from 1970, but the bottom reached about 180°C—hotter than expected—and it stopped here. The hole is only 23 cm wide. Tiny plankton fossils turned up about 6 km down.
5–20km
Inland earthquakes
Most earthquakes under inland Japan happen in the crust, about 5–20 km down.
~20–30km
The Philippine Sea Plate
The Philippine Sea Plate dives under Japan from the south. Directly beneath Tokyo, for example, you hit it at about 20–30 km. It is one of the places feared as the source of a future Tokyo earthquake.
35–2,891 kmThe Mantle
A layer of hot rock reaching from the bottom of the crust down to 2,900 km. It makes up more than 80% of Earth's volume.
~35km
The Moho
The boundary between crust and mantle. In 1909, Croatian seismologist Andrija Mohorovičić found it as the depth where earthquake waves suddenly change speed.
35km+
Peridotite
Most of the mantle is peridotite. Its main mineral, olivine, is the same as the gemstone peridot.
~70–100km
The Pacific Plate
The Pacific Plate sinks under Japan from the east; directly below Tokyo it lies about 70–100 km down. Three plates are stacked under Tokyo, a rare arrangement anywhere in the world.
100kmAs far as the edge of space (100 km up)
~100km
Where magma is born
Beneath Japan's volcanoes, water is squeezed out of the sinking plate at around 100 km. Adding water makes mantle rock melt more easily, and magma is born.
~100km
A cold plate
The sinking plate spent ages cooling under the ocean, so it is hundreds of degrees colder than the mantle around it. Around 100 km below Japan, the mantle is surprisingly “cold.”
150–200km
The pressure that makes diamonds
At 150–200 km, the pressure is about 50,000–60,000 atmospheres. Under old continents it turns carbon into diamond. Diamonds on the surface were carried up in an instant by special volcanic eruptions.
~100–400km
Rock that flows
The mantle below the plates is solid, but over long spans of time it flows slowly, like thick syrup. The plates glide on top of it.
~400kmAs far as the ISS's altitude, or Tokyo to Osaka, straight down
410km
Minerals transform
Under crushing pressure, olivine's atoms rearrange into a denser mineral, wadsleyite. Earthquake waves change speed here too.
520km
A blue mineral and a hidden ocean
Deeper still, it becomes the blue mineral ringwoodite, which can store water inside its crystals. In 2014, water-bearing ringwoodite was found inside a diamond from Brazil. There may be as much water down here as in the oceans.
660–2,891 kmThe Lower Mantle
From here down to 2,900 km is the lower mantle, the largest layer of the Earth.
682km
A deep earthquake
On May 30, 2015, a magnitude 8.1 quake struck about 680 km beneath the sea west of the Ogasawara Islands, and shaking was recorded in all 47 prefectures of Japan. It happened inside the Pacific Plate that has sunk beneath Japan.
833kmAs far as Tokyo to Sapporo
660–2,700km
Bridgmanite
The star of the lower mantle and the most abundant mineral on Earth, yet a natural crystal wasn't found and named until 2014, inside a meteorite that fell in Australia.
whole Earth
A CT scan of the Earth
No one has ever been here. We learn what is inside the Earth through seismic tomography, which combines how earthquake waves recorded around the world travel, like a CT scan.
1,559kmAs far as Tokyo to Naha, Okinawa
whole mantle
Mantle convection
Although the mantle is solid rock, it churns over hundreds of millions of years at a few centimeters a year, about as fast as fingernails grow. This flow moves the plates and drives earthquakes and volcanoes.
2,099kmAs far as Tokyo to Beijing
to 2,900km
The plate graveyard
Some sunken plates are thought to sink all the way to the bottom of the mantle over tens to hundreds of millions of years and pile up there.
~2,600–2,900km
Post-perovskite
The very bottom layer of the mantle (the D″ layer). In 2004, a Japanese team including Kei Hirose showed in experiments that the minerals change into yet another form here.
2,885kmAs far as Tokyo to Hong Kong
2,891–5,150 kmThe Outer Core
The world of rock ends, and a sea of molten metal begins. Down to 5,150 km, it is all liquid iron.
2,891km
The core–mantle boundary
The biggest boundary inside the Earth: rock above, liquid metal below. Density nearly doubles at once. Seismologist Beno Gutenberg pinned down this depth in 1914. Gravity is strongest here, about 1.09 times that at the surface.
2,891–5,150km
A sea of liquid iron
The outer core is an ocean of molten iron and nickel, from around 4,000°C to over 5,000°C. Even so, it flows freely as a liquid.
3,474kmAs far as the Moon's diameter
3,800km
The earthquake “shadow”
S-waves, one kind of earthquake shaking, cannot travel through liquid. They leave a “shadow” on the far side of the Earth where they never arrive. That is how we know the outer core is liquid.
4,300km
Iron whirlpools
The outer core's iron flows slowly, about 10 km a year, and is swung around by Earth's rotation into swirls.
4,609kmAs far as Tokyo to Bangkok
5,150–6,371 kmThe Inner Core
A solid ball of iron floating inside the liquid outer core.
5,150km
The Lehmann discontinuity
In 1936, Danish seismologist Inge Lehmann discovered a second, solid core inside the outer core.
5,320kmAs far as Tokyo to Singapore
5,150–6,371km
A solid iron ball
The inner core is a ball of iron about 1,220 km in radius, roughly 70% the size of the Moon. It's as hot as the surface of the Sun, yet the immense pressure keeps it solid.
5,900km
The spinning inner core
The inner core seems to rotate at a slightly different speed from the rest of the planet. A 2023 study even suggested the difference stopped around 2009 and may have reversed. It's still full of mysteries.
6,199kmAs far as Tokyo to Honolulu
6,371 km downThe Center of the Earth
6,371 km from the surface. Gravity here is zero. Nothing pulls on your body; you'd simply float.
Past the centerUp to the other side
From here on, depths are the distance left to the surface on the other side.
Center
Data at the center
Pressure about 3.6 million atmospheres; temperature an estimated 5,000–6,000°C. Jump into the hole and you'd get here in about 19 minutes, passing through at about 9.9 km/s (about 35,700 km/h).
6,050km to surface
Aligned crystals
Earthquake waves cross the inner core a few percent faster north–south than east–west, probably because its iron crystals are lined up.
5,650km to surface
A growing inner core
Iron from the outer core slowly freezes onto it, so the inner core is still growing. A leading view now holds that it formed around 500 million to 1 billion years ago.
7,483kmYou've dug as far as Tokyo to Moscow
the far sideThe Outer Core
Back into the sea of liquid iron. This is where Earth's magnetic field is born.
4,800km to surface
The dynamo
As liquid iron swirls through the outer core it generates electric currents, and those currents create Earth's magnetic field. It's why a compass points north.
4,100km to surface
An invisible shield
Earth’s magnetic field shields the surface from particles streaming from the Sun (the solar wind). Auroras are particles slipping through the gaps and making the air glow.
8,810kmYou've dug as far as Tokyo to Los Angeles
3,550km to surface
Magnetic reversals and the Chibanian
Earth's magnetic poles have swapped north and south many times. The last flip was about 770,000 years ago. Rock layers in Ichihara, Chiba, that record it gave their name to a geologic age, the Chibanian (about 774,000 to 129,000 years ago), in 2020.
9,562kmYou've dug as far as Tokyo to London
3,000km to surface
The South Atlantic Anomaly
The sky over South America, where you're headed, lies within the South Atlantic Anomaly, where Earth's magnetic field is especially weak. Satellites passing through it are prone to glitches.
the far sideThe Mantle
Back into the world of rock: about 2,900 km of hot rock to climb.
2,620km to surface
Giant blobs at the base of the mantle
At the bottom of the mantle sit two enormous masses of rock, each the size of a continent: one under Africa, one under the Pacific. No one knows yet what they are.
2,350km to surface
The birth of the core
About 4.6 billion years ago, the newborn Earth's surface was a sea of magma. Heavy iron sank to the center to form the core, and lighter rock floated up to form the mantle.
2,000km to surface
Plumes
Hot rock rises from deep in the mantle like smoke. About 130 million years ago, the head of a plume is thought to have reached the area beneath the join between South America and Africa, flooding the surface with lava. That lava is the basalt plateau you're about to pass through.
10,847kmYou've dug as far as Tokyo to New York
1,600km to surface
Where Earth's heat comes from
About half the heat flowing out of Earth's interior comes from uranium and thorium decaying in the rock. In 2011, the KamLAND detector deep in the Kamioka mine in Gifu, Japan, showed this by catching neutrinos coming from inside the Earth.
1,200km to surface
A planet made mostly of rock
The mantle is more than 80% of Earth's volume. Earth is mostly a hot ball of rock; the oceans and continents are just a thin skin on its surface.
780km to surface
A diamond from the lower mantle
In 2021, a mineral formed in the lower mantle, deeper than 660 km, was found in nature for the first time, inside a diamond from Botswana. It was named davemaoite.
520km to surface
Ringwoodite again
Past 660 km you enter the transition zone. Blue ringwoodite, wadsleyite, olivine: the minerals change in the reverse order of the way down.
400km left400 km to go, the altitude of the ISS
300km to surface
The plume's pathway
Beneath the Paraná Basin (a few hundred km north of here), a column where earthquake waves travel more slowly than their surroundings extends hundreds of kilometers down. It is thought to be the trail of the plume behind the great eruption 130 million years ago (reported in 1995).
220km to surface
A subduction zone on this side
About 2,000 km west of here, on the western edge of the South American Plate, the Pacific's Nazca Plate sinks beneath it, raising the Andes and their volcanoes: the same mechanism that built the Japanese islands.
~150km
The roots of a continent
The plates under continents are far thicker than those under oceans. Beneath South America, a cold, rigid “keel” is thought to extend to about 150 km.
100km to surface
The South American Plate
The South American Plate, which carries the continent, moves west a few centimeters a year, as if pushed from the ridge in the middle of the Atlantic.
60km to surface
Continents that won't sink
Continental rock is light, so unlike ocean plates it doesn't sink into the mantle. That's why continents still hold rocks nearly 4 billion years old, while the oldest seafloor is only about 200 million years old.
South AmericaContinental Crust
The far side is the South American continent. The crust here is about 40 km thick, much thicker than the crust beneath Japan.
25km to surface
Quiet ground
A world apart from Japan's underground. This region is far from any plate boundary, and large earthquakes almost never happen.
~5–40km
Ancient continental rock
Most of the crust is old rock, granite and gneiss, formed hundreds of millions to billions of years ago. It has stayed here all along as the continent's foundation.
12,262m leftOne Kola Superdeep Borehole left to the surface
8,849m leftOne Mount Everest left to the surface
~4–40km
The basin's foundation
Beneath the Paraná Basin's layers lies the continent's foundation (basement rock). The basin formed as this foundation slowly sank over hundreds of millions of years and sediment filled the hollow.
BrazilThe Paraná Basin
A giant depression in South America about four times the size of Japan. Over more than 400 million years, ocean mud, glacial stones, desert sand and lava piled up here.
~4km (est.)
A sea 400 million years ago
About 400 million years ago (the Devonian), this was a shallow seafloor. In Ponta Grossa, Paraná, these layers yield fossils of trilobites and lingulid brachiopods.
3,776m leftOne Mount Fuji left to the surface
~3–4km (est.)
An age of glaciers
About 300 million years ago, South America, Africa, Antarctica, India and more were joined in one continent, Gondwana, and this area lay under thick glaciers. Stones carried by the ice remain scattered through the mud.
~2.7km (est.)
Forests that became coal
After the glaciers melted, forests of Glossopteris, a plant with tongue-shaped leaves, spread here and turned into coal. Fossils of the same plant are found in Antarctica and India.
~2.5km (est.)
Rock that burns
Some of the black shale (the Irati Formation) contains oil. In São Mateus do Sul, Paraná, this rock is mined where it comes near the surface and heated to extract oil and gas.
~2.5km (est.)
Mesosaurus
A small, slender-snouted reptile that lived by the water about 280 million years ago. Finding the same fossils in southern Africa became one piece of evidence for Wegener's idea that the continents were once joined.
1,900m to surface
One continent
Until a little over 100 million years ago, South America and Africa were a single landmass. Because their coastlines fit like puzzle pieces, Wegener proposed continental drift in 1912.
~1–2km
Drilled for oil, found hot springs
In the Paraná Basin, several towns got hot springs from wells drilled in search of oil. In Piratuba, Santa Catarina, hot water gushed from a well about 2,200 m deep in 1964, and it is now a spa town.
~1km (est.)
Land that was desert
About 140 million years ago, this was desert as far as the eye could see. The sandstone formed from its dunes holds footprints of dinosaurs and other animals; in Araraquara, São Paulo, about 1,000 were found in sidewalks paved with this stone.
~1km (est.)
The Guarani Aquifer
Huge amounts of groundwater fill the spaces between the sandstone's grains. Spanning Brazil, Argentina, Paraguay and Uruguay, it is one of the world's largest stores of groundwater.
BrazilThe Lava Plateau
About 130 million years ago, lava poured out for hundreds of thousands of years, hardening into dozens of stacked layers of basalt. Around here it is several hundred to nearly 1,000 m thick.
650m to surface
One of the largest eruptions in Earth's history
The lava is estimated to have originally exceeded 2.3 million km³. Thick lava covered an area more than twice the size of Japan.
634m leftOne Tokyo Skytree left to the surface
400m to surface
Iguazu Falls
About 200 km west of here, Iguazu Falls tumbles down steps formed by these basalt layers. The drop is up to about 80 m.
333m leftOne Tokyo Tower left to the surface
250m to surface
Amethyst geodes
In gas bubbles left as the lava cooled, crystals of amethyst slowly grew. Rio Grande do Sul, to the south, is one of the world’s leading sources.
120m to surface
Water in the cracks
Groundwater that seeps into cracks in the basalt is pumped up from wells for drinking and farming.
40m to surface
Basalt columns
When thick lava cools slowly and shrinks, it cracks into hexagonal columns (columnar jointing).
~1–10m
Rock turns to soil
Near the surface, rain and heat slowly break the basalt down into red soil over long ages. The red soil here is often several meters thick.
to ~8m
Leafcutter ant nests
These ants grow “mushroom farms” on leaves they cut. Their nests spread several meters underground; one nest studied by pouring in cement reached about 8 m deep.
2.5m to surface
Paraná pine roots
The Paraná pine (Araucaria) is the symbol of Paraná. In winter, people boil and eat pinhão, the seeds from its big cones. It is now endangered.
~1–2m
Under the town
Under Pato Branco's streets, too, run water pipes, power lines and telecom cables. On the other side of the world, the ground under a town looks a bit like Japan's.
90cm to surface
Burrowing owls
Small owls that dig holes in the ground for nests. In Brazil they are a common sight in fields and on vacant lots in town.
45cm to surface
Soybean roots’ “fertilizer factories”
Bacteria living in nodules on soybean roots turn nitrogen from the air into nutrients. Thanks to them, Brazil's soybean farmers don't need to spread nitrogen fertilizer.
20cm to surface
Red soil
Iron-rich red soil (terra roxa) formed from weathered basalt. It is very fertile, and Paraná is Brazil's second-largest soybean producer.