Field
Earth
Ice, ocean, and the weather this planet insists on.
30 entries
The Earth is not a sphere
Earth is an oblate spheroid. The equatorial radius is about 21 kilometres longer than the polar radius.
Antarctica is a desert
The interior of Antarctica receives so little precipitation that it is the largest desert on Earth.
The Sahara was green
Between about 11,000 and 5,000 years ago the Sahara held lakes, grasslands, and people.
A lake sits under four kilometres of ice
Lake Vostok, in East Antarctica, is a liquid freshwater lake about 250 kilometres long, sealed under roughly four kilometres of ice.
The longest mountain chain is underwater
The mid-ocean ridge system runs about 65,000 kilometres, longer than the Andes and the Rockies combined, and almost all of it is submerged.
A lake emptied across a province
Near the end of the last ice age, glacial Lake Missoula burst repeatedly and sent floods across what is now eastern Washington, carving the Channeled Scablands.
The Earth rings after a great earthquake
A very large earthquake sets the whole planet into free oscillation. The tones can be recorded for days.
Most fresh water is ice
About two thirds of the fresh water on Earth is locked in ice sheets and glaciers, and almost all of that ice is in Antarctica.
A cloud weighs hundreds of tonnes
A modest fair-weather cumulus, about a kilometre on a side, holds on the order of a few hundred tonnes of liquid water.
Raindrops are not tears
Small raindrops are spheres. Large ones are flattened on the bottom, like hamburger buns. None of them are teardrops.
Some dunes sing
Certain dry sand dunes emit a loud, sustained low note when sand avalanches down their slip face.
Some lightning never comes down
Above large thunderstorms the upper atmosphere flashes upward: red sprites, blue jets, and elves, kilometres above the cloud tops.
A volcano cancelled a summer
The April 1815 eruption of Tambora cooled the planet enough that 1816 was, in many places, the year without a summer.
Some rivers never find the sea
In an endorheic basin, rivers end in a lake or a salt flat. The Okavango dies in a delta in the Kalahari and does not reach an ocean.
Australia is wider than the Moon
The Australian mainland, east to west, spans about 4,000 kilometres. The Moon’s diameter is about 3,475. The Pacific is several times wider still.
The Mediterranean dried up
Around six million years ago the Mediterranean basin largely evaporated, leaving salt kilometres thick. When the Atlantic broke back in, the sea returned in a flood.
The solid core is about as hot as the Sun’s face
Iron at the boundary of the inner core is estimated near 6,200 kelvin, comparable to the surface of the Sun. The pressure keeps it solid, and the ball is growing.
A diamond carried a wet mineral up from the mantle
Ringwoodite trapped inside a diamond contained about one percent water by weight. If the mantle’s transition zone is like that sample, it holds as much water as the oceans.
The Earth hums when no earthquake is happening
The planet oscillates continuously, at periods of a few minutes, with amplitudes of nanometres, even in the absence of large quakes.
One ocean current beats every river
The Florida Current carries about thirty million cubic metres of water a second. All the rivers on Earth, together, carry about one million.
Water has sat in the crust for a billion years
Brine from a mine in Timmins, Ontario, has a minimum residence time of about 1.5 billion years. The dating is from xenon isotopes that match an ancient atmosphere.
The sailing stones are pushed by ice the thickness of a window
Rocks on Racetrack Playa leave long trails across flat mud. In 2013 they were watched moving, shoved by thin sheets of ice in a light wind.
The ozone overhead would make a layer three millimetres thick
If every ozone molecule above you were brought to sea-level pressure and zero celsius, it would form a layer about three millimetres thick. Spread out, that is the shield.
A nuclear reactor ran in Gabon with no one to build it
About 1.7 billion years ago, uranium ore at Oklo went critical. Groundwater was the moderator. The fission products are still in the rock.
A wave twice as high as the sea around it was measured
On 1 January 1995 a laser on the Draupner platform recorded a wave 25.6 metres high, in a sea whose significant wave height was about 12 metres. It was the first rogue wave caught by an instrument.
In deep water a tsunami is a low swell moving at jet speed
A tsunami in the open ocean is often under a metre high and hundreds of kilometres long, travelling at about 700 to 800 kilometres an hour. It stands up only when the sea becomes shallow.
The compass has pointed south
Earth's magnetic field has reversed, many times. The ocean floor is striped with the record: rock that froze while the compass pointed the other way.
The air above you weighs about a kilogram on every square centimetre
Sea-level pressure is about 101,000 pascals. That is the weight of a kilogram pressing on each square centimetre of you, from every direction at once.
Thunderclouds fire beams of antimatter upward
A terrestrial gamma-ray flash in a storm makes pairs of electrons and positrons. NASA's Fermi telescope has caught the positrons travelling out along Earth's magnetic field, including from storms over the horizon.
The Amazon is fertilised by dust from the Sahara
Satellite measurements trace a plume of African dust across the Atlantic and onto the Amazon, carrying on the order of twenty thousand tonnes of phosphorus a year. The forest's soil is poor. The desert makes up some of the difference.