Elements present on Earth

1. How much surface area does Earth contain?

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

42. What is the largest lake in the world?

By size and volume it is the Caspian Sea, located between southeast Europe and west Asia.

43. Where do most earthquakes and volcanic eruptions occur on Earth?

The majority occur along boundaries of the dozen or so major plates that more or less float on the surface of Earth. One of the most active plate boundaries where earthquakes and eruptions are frequent, for example, is around the massive Pacific Plate commonly referred to as the Pacific Ring of Fire. It fuels shaking and baking from Japan to Alaska to South America.

44. How hot are the planet's innards?

The temperature of Earth increases about 36 degrees Fahrenheit (20 degrees Celsius) for every kilometer (about 0.62 miles) you go down. Near the center, its thought to be at least 7,000 degrees Fahrenheit (3,870 Celsius).

45. What three countries have the greatest number of historically active volcanoes?

The top three countries are Indonesia, Japan, and the United States in descending order of activity.

46. How many people worldwide are at risk from volcanoes?

As of the year 2000, USGS scientists estimated that volcanoes posed a tangible risk to at least 500 million people. This is comparable to the entire population of the world at the beginning of the seventeenth century!

47. Which of the following sources stores the greatest volume of fresh water worldwide: lakes, streams or ground water?

Groundwater comprises a 30 times greater volume than all freshwater lakes, and more than 3,000 times what's in the world’s streams and rivers at any given time. Groundwater is housed in natural underground aquifers, in which the water typically runs around and through the stone and other material.

48. Which earthquake was larger, the 1906 San Francisco earthquake or the 1964 Anchorage, Alaska, temblor?

The Anchorage earthquake had a magnitude of 9.2, whereas the San Francisco earthquake was a magnitude 7.8. This difference in magnitude equates to 125 times more energy being released in the 1964 quake and accounts for why the Anchorage earthquake was felt over an area of almost 500,000 square miles (1,295,000 square kilometers).

49. Which earthquake was more destructive in terms of loss of life and relative damage costs, the 1906 San Francisco earthquake or the 1964 Anchorage earthquake?

The 1906 San Francisco earthquake tops this category. It was responsible for 700 deaths versus 114 from the Anchorage earthquake. Property damage in San Francisco was also greater in relative terms due to the destructive fires that destroyed mostly wooden structures of the time.

50. Is Earth's core solid?

The inner portion of the core is thought to be solid. But the outer portion of the core appears molten. We've never been there though, so scientists aren't sure of the exact composition. A radical Hollywood-like idea was recently put forth to blow a crack in the planet and send a probe down there to learn more. An interesting bit of recent evidence shows Mars' core may be similarly squishy. Scientists figured this out by studying tides on Mars (tides on Mars?).