🌍 #12 answers: Planet Earth Day

The surface of Earth's inner core is thought to be about 5,400 °C, roughly as hot as the surface of the Sun.

It stays solid because of the huge pressure at the centre.

“The temperature at its surface is estimated to be approximately 5,700 K (5,430 °C; 9,800 °F), about the temperature at the surface of the Sun.”

Earth isn't a perfect ball: it bulges slightly around the equator because of the way the planet spins.

The equator is about 43 km wider than the pole-to-pole distance.

“An equatorial bulge is a difference between the equatorial and polar diameters of a planet, due to the centrifugal force exerted by the rotation about the body's axis.”

Pumice is a volcanic rock so full of holes that it floats on water, sometimes for years.

It forms when gas bubbles get frozen into cooling lava. Eventually it soaks up water and sinks.

“Pumice has a porosity of 64–85% by volume and it floats on water, possibly for years, until it eventually becomes waterlogged and sinks.”

The Giant's Causeway is made up of tens of thousands of interlocking basalt columns left by an ancient eruption.

There are about 40,000 of them. Most of the columns on this Northern Irish coast are six-sided, formed as lava cooled and cracked.

“The Giant's Causeway (Irish: Clochán an Aifir or Clochán na bhFomhórach) is an area of approximately 40,000 interlocking basalt columns, the result of an ancient volcanic fissure eruption, part of the North Atlantic Igneous Province active in the region during the Paleogene period.”

The rock near the top of Mount Everest is limestone containing tiny fragments of ancient sea creatures.

Samples include bits of trilobites, crinoids and ostracods from an ancient seabed.

“Later petrographic analysis of samples of the limestone from near the summit revealed them to be composed of carbonate pellets and finely fragmented remains of trilobites, crinoids, and ostracods.”

Measured from its base on the sea floor, Mauna Kea in Hawaii is taller than Mount Everest.

Most of the volcano is hidden under the Pacific Ocean.

“This dry prominence is greater than Everest's height above sea level of 8,848.86 metres or 29,031.7 feet, and some authorities have labeled Mauna Kea the tallest mountain in the world, from its underwater base.”

Some of Hawaii's famous white-sand beaches come from the poop of parrotfish.

Parrotfish scrape coral with beak-like teeth, grind it up and excrete it as sand.

“The famous white-sand beaches of Hawaii, for example, actually come from the poop of parrotfish.”

Lodestone is a rock that is naturally magnetic, and hanging pieces of it made the first compasses.

Its name means 'leading stone' in Middle English.

“Pieces of lodestone, suspended so they could turn, were the first magnetic compasses, and their importance to early navigation is indicated by the name lodestone, which in Middle English means "course stone" or "leading stone",”

In 1772 the chemist Antoine Lavoisier burned a diamond using a lens and sunlight to show what it was made of.

The only thing produced was carbon dioxide, proving diamond is carbon.

“In 1772, the French scientist Antoine Lavoisier used a lens to concentrate the rays of the sun on a diamond in an atmosphere of oxygen, and showed that the only product of the combustion was carbon dioxide, proving that diamond is composed of carbon.”

The Hoba meteorite weighs over 60 tonnes and has never been moved from the spot where it fell.

A farmer in Namibia found it in 1920 while ploughing his field.

“It has been uncovered, but because of its large mass, has never been moved from where it fell. The main mass (some parts have apparently been chopped off) is estimated at more than 60 tonnes.”