What was the biggest volcanic eruption in the United States?

The most recent notable volcanic eruption in the United States was the eruption of Mount St. Helens on May 18, 1980, in the state of Washington, in which more than 50 people were killed. Most other volcanoes in the United States are not active and have not been for many years.

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What causes the distance from Earth to the Moon to vary?

The celestial mechanics of the Moon's motion are very complex. When the distance to the Moon is measured at different times of the month, it is found to vary by more than 10 percent because the Moon's orbit is basically an ellipse, with Earth at one focus. The Moon may come as close as 356,334 kilometers (220,927 miles) to Earth's center and then move as far away from it as 406,610 kilometers (252,098 miles). The dates when the Moon is at apogee (the point in its orbit farthest from Earth) and perigee (the point in its orbit closest to Earth) can be found on each month's calendar page in The Old Farmer's Almanac. However, to understand the "mechanics," as mentioned above, we recommend consulting a basic astronomy textbook.

Is the Atlantic Ocean warmer than the Pacific Ocean?

Although it might seem illogical, the Atlantic Ocean is warmer. For any given latitude, the Atlantic Ocean has proved to be about 16 degrees F (9 degrees C) warmer than the Pacific Ocean off the U.S. coast -- quite a difference.

What is the percentage of farmland versus developed land in the United States?

The total area of the United States is 2,262.5 million acres. Of this, 931.8 million acres are used for agriculture, amounting to 41.2 percent of the total U.S. land area. Actual cropland is only 431.1 million acres, or 19.1 percent of the land area. By contrast, the United States has 58.9 million acres of urban land, or 2.6 percent of the total land area.

The year 1961 is readable forward, backward, and upside down. What is the next year when this will occur?

Unless medical technology increases very rapidly, none of us will be around to see this numerical palindrome when it happens again in 6009.

Why is every snowflake different?

Modern physics has made great progress toward explaining the genesis of the snowflake's form. Its hexagonal symmetry has its origin in the shape of a water molecule, which consists of an atom of oxygen and two atoms of hydrogen. They are connected in such a way that the hydrogen "arms" make an angle like the arms on the letter x. This angle ensures that when the water molecules link to form a crystal, the resultant symmetry will be hexagonal. Regarding the probabilities of combination, a single snow crystal consists of something like one quintillion molecules of water. The number of ways that many molecules can be arranged into six-sided crystals is astronomical. So the odds are huge that no two snowflakes have ever been exactly alike.

What is the full definition of sunrise and sunset?

The point on the celestial sphere directly above an observer is called the zenith. The great circle on this sphere exactly 90 degrees in every direction from the zenith is called the (astronomical) horizon. If the observer is on a flat surface, like the ocean, and has his or her eye on the surface, sunrise or sunset occurs when the upper edge (called upper limb) of the Sun disk intersects with the horizon. Realty is a bit more complex. Light passing through the atmosphere is refracted and bent downward, giving the observer the impression that the object is higher in the sky than it really is. The nearer the object is to the horizon, the larger it appears. When the lower limb of the Sun appears to touch the horizon, the Sun has already gone below it because the refraction "lifts" the Sun by more than the diameter of the Sun disk. Of course, all this means nothing if you happen to live in the shadow of a mountain. Near where I live on the Ohio River is a small town by the name of Shadyside. A high hill on the western edge of town puts it in the shade of the hill hours before true, astronomical sunset.

Is it true that you can tell how high the snow will be by looking at how high the bees build their nests?

There's an old saying, "When hornets build their nests near the ground, expect a cold and early winter." We haven't heard one about bees but think the same saying could apply.

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