Amazing Earth Facts - Part I

We live on a sphere of extremes and oddities. In fact it's not really a sphere, but it is a wild planet, mottled with deadly volcanoes, rattled by killer earthquakes, drenched in disastrous deluges. But do you know which were the worst?

Some of Earth's valleys dip below sea level. Mountains soar into thin air. Can you name the lowest spot? The tallest peak? Do you know how far it is to the center of the planet or what's there?

Where are the planet's hottest, coldest, driest and windiest places?

The following list of Earth's extremes and other amazing facts is presented in Q&A format, so you can cover the answers to test your knowledge of the home planet. Sources include the U.S. Geological Survey and the National Oceanic and Atmospheric Administration, with other SPACE.com reporting.

1. What is the hottest place on Earth?

Count one wrong if you guessed Death Valley in California. True enough on many days. But El Azizia in Libya recorded a temperature of 136 degrees Fahrenheit (57.8 Celsius) on Sept. 13, 1922 -- the hottest ever measured. In Death Valley, it got up to 134 Fahrenheit on July 10, 1913.

2. And the coldest place around here?

Far and away, the coldest temperature ever measured on Earth was -129 Fahrenheit (-89 Celsius) at Vostok, Antarctica, on July 21, 1983.

3. What makes thunder?

If you thought, "Lightning!" then hats off to you. But I had a more illuminating answer in mind. The air around a lightning bolt is superheated to about five times the temperature of the Sun. This sudden heating causes the air to expand faster than the speed of sound, which compresses the air and forms a shock wave; we hear it as thunder.

4. Can rocks float?

In a volcanic eruption, the violent separation of gas from lava produces a "frothy" rock called pumice, loaded with gas bubbles. Some of it can float, geologists say. I've never seen this happen, and I'm thankful for that.

5. Can rocks grow?

Yes, but observing the process is less interesting than watching paint dry. Rocks called iron-manganese crusts grow on mountains under the sea. The crusts precipitate material slowly from seawater, growing about 1 millimeter every million years. Your fingernails grow about the same amount every two weeks.

6. How much space dust falls to Earth each year?

Estimates vary, but the USGS says at least 1,000 million grams, or roughly 1,000 tons of material enters the atmosphere every year and makes its way to Earths surface. One group of scientists claims microbes rain down from space, too, and that extraterrestrial organisms are responsible for flu epidemics . There's been no proof of this, and I'm not holding my breath.