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100 Amazing Earth Facts

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21. Good thing California isn't sinking further, right?

Actually parts of it are, which is so interesting that I snuck this non-question onto the list. In a problem repeated elsewhere in the country, the pumping of natural underground water reservoirs in California is causing the ground to sink up to 4 inches (11 centimeters) per year in places. Water and sewage systems may soon be threatened.

22. What is the longest river?

The Nile River in Africa is 4,160 miles (6,695 kilometers) long.

23. What is the most earthquake-prone state in the United States?

Alaska experiences a magnitude 7 earthquake almost every year, and a magnitude 8 or greater earthquake on average every 14 years. Florida and North Dakota get the fewest earthquakes in the states, even fewer than New York.

24. What's the driest place on Earth?

A place called Arica, in Chile, gets just 0.03 inches (0.76 millimeters) of rain per year. At that rate, it would take a century to fill a coffee cup.

25. What causes a landslide?

Intense rainfall over a short period of time can trigger shallow, fast-moving mud and debris flows. Slow, steady rainfall over a long period of time may trigger deeper, slow-moving landslides. Different materials behave differently, too. Every year as much as $2 billion in landslide damage occurs in the United States. In a record-breaking storm in the San Francisco area in January 1982, some 18,000 debris flows were triggered during a single night! Property damage was over $66 million, and 25 people died.

26. How fast can mud flow?

Debris flows are like mud avalanches that can move at speeds in excess of 100 mph (160 kph).

27. Do things inside Earth flow?

You bet. In fact, scientists found in 1999 that molten material in and around Earth's core moves in vortices, swirling pockets whose dynamics are similar to tornadoes and hurricanes. And as you'll learn later in this list, the planet's core moves in other strange ways, too.

28. What is the wettest place on Earth?

Lloro, Colombia averages 523.6 inches of rainfall a year, or more than 40 feet (13 meters). That's about 10 times more than fairly wet major cities in Europe or the United States.

29. Does Earth go through phases, like the Moon?

From Mars, Earth would be seen to go through distinct phases (just as we see Venus change phases). Earth is inside the orbit of Mars, and as the two planets travel around the Sun, sunlight would strike our home planet from different angles during the year. Earth phases can be seen in recent photographs taken by Mars Global Surveyor and the European Mars Express.

30. What is the largest canyon?

The Grand Canyon is billed as the world's largest canyon system. Its main branch is 277 miles (446 kilometers) long. But let's compare. Valles Marineris on Mars extends for about 3,000 miles (4,800 kilometers). If added it to a U.S. map, it would stretch from New York City to Los Angeles. In places this vast scar on the Martian surface is 5 miles (8 kilometers) deep.

31. What is the deepest canyon in the United States?

Over the eons, the Snake River dug Hell's Canyon along the Oregon-Idaho border. It is more than 8,000 feet (2.4 kilometers) deep. In contrast, the Grand Canyon is less than 6,000 feet deep -- a bit more than a mile.

32. Is Earth the largest rocky planet in the solar system?

Just barely! Earth's diameter at the equator is 7,926 miles (12,756 kilometers). Venus is 7,521 miles (12,104 kilometers) wide. Mercury and Mars, the other two inner rocky planets, are much smaller. Pluto is rocky, too, but it's comparatively tiny (and some say it is not a planet at all).

33. How many of Earth's volcanoes are known to have erupted in historic time?

About 540 volcanoes on land are known. No one knows how many undersea volcanoes have erupted through history.

34. Is air mostly oxygen?

Earth's atmosphere is actually about 80 percent nitrogen. Most of the rest is oxygen, with tiny amounts of other stuff thrown in.

35. What is the highest waterfall in the United States?

Yosemite Falls in California is 2,425 feet (739 meters).

36. What percentage of the world's water is in the oceans?

About 97 percent. Oceans make up about two-thirds of Earth's surface, which means that when the next asteroid hits the planet, odds are good it will splash down.

37. Which two landmasses contain the vast majority of the Earth's fresh water supply?

Nearly 70 percent of the Earth's fresh-water supply is locked up in the icecaps of Antarctica and Greenland. The remaining fresh-water supply exists in the atmosphere, streams, lakes, or groundwater and accounts for a mere 1 percent of the Earth's total.

38. Which of the Earth's oceans is the largest?

The Pacific Ocean covers 64 million square miles (165 million square kilometers). It is more than two times the size of the Atlantic. It has an average depth of 2.4 miles (3.9 kilometers).

39. Why is Earth mostly crater-free compared to the pockmarked Moon?

Earth is more active, in terms of both geology and weather. Much of our planet's geologic history was long ago folded back inside. Some of that is regurgitated by volcanoes, but the results are pretty hard to study. Even more recent events evident on the surface -- craters that can by millions of years old -- get overgrown by vegetation, weathered by wind and rain, and modified by earthquakes and landslides. The Moon, meanwhile, is geologically quiet and has almost no weather; its craters tell a billions-year-long tale of catastrophic collisions. Interestingly, some of the oldest Earth rocks might be awaiting discovery on the Moon, having been blasted there billions of years ago by the very asteroid impacts that rattle both worlds.

40. How much surface area does Earth contain?

There are 196,950,711 square miles (510,100,000 square kilometers).