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How often does the Yellowstone super volcano erupt?
Three extremely large explosive eruptions have occurred at Yellowstone in the past 2.1 million years with a recurrence interval of about 600,000 to 800,000 years. More frequent eruptions of basalt and rhyolite lava flows have occurred before and after the large caldera-forming events.

How many professional football teams are there in the USA?
Out of the league's 32 teams, six (four division winners and two wild-card teams) from each conference compete in the NFL playoffs, a single-elimination tournament culminating in the Super Bowl, played between the champions of the NFC and AFC. The champions of the Super Bowl are awarded the Vince Lombardi Trophy.

Who chopped down the cherry tree and why?
Myth: George Washington once chopped down his father's favorite cherry tree. The story goes that a young George was about six years old and had been given a hatchet, which he enthusiastically used to chop at just about anything in sight.

Is violet blue or purple?
In the traditional color wheel used by painters, violet and purple are both placed between red and blue. Purple occupies the space closer to red, between crimson and violet. Violet is closer to blue, and usually less intense and bright than purple.

How can you tell if a pearl is real?
The Tooth Test – Rub the pearls lightly along the biting edge of your upper front teeth. If they feel slightly rough, sandy or gritty, it's likely they are cultured or natural pearls because of the layers of nacre that have formed over time. If they feel smooth or glassy, they are probably imitations.

Why is it called Big Ben?
The origin of the nickname Big Ben is the subject of some debate. The nickname was applied first to the Great Bell; it may have been named after Sir Benjamin Hall, who oversaw the installation of the Great Bell, or after boxing's English Heavyweight Champion Benjamin Caunt.