1-There are 18 volcanoes in the US with the potential to erupt again, all of them in Alaska, Hawaii and the West Coast states.
2-Rubies and sapphires are actually the same mineral - corundum. The basic chemical formula of corundum is Al2O3, but traces of iron stain the mineral red (ruby) while traces of chromium or titanium stain the mineral blue (sapphire).
3-Rubies, sapphires and emeralds are all more rare than diamonds.
4-Not all diamonds are transparent. They come in a variety of colors (called "fancies"), including yellow, green, blue, orange, brown ("champagne"), purple, grey, black (called carbanado, recently shown to be meteroic), milky white, pink, and red. Red is by far the rarest.
5-Antacids taste like chalk because they ARE chalk, a.k.a. calcium carbonate.
6-Will Yellowstone spawn a "supervolcano" that will destroy the US? ANSWER: Probably not. The amount of rhyolitic magma just beneath the surface of Yosemite is relatively small at present, so even if it eventually "erupts" through the surface, should cause minor lava flows rather than a large supervolcano-type eruption. (For those who are still hoping the Mayans were onto something, however, a supervolcano-type eruption is technically possible. USGS sets the odds of such an event occuring in the next few thousand years at 0.00014% .)
7-The Gulf of California is a spreading zone - many millions of years from now, it will be an ocean.
8-The earth is slipping along the San Andreas fault at a rate of about 2" per year. This means that in about 15 millions years Los Angeles and San Francisco will be neighbors.
9-The Great Lakes, combined, contain more than 20% of the world's available fresh water. (Doesn't count underground aquafers or polar ice)
10-People experiencing earthquakes in the Great Lakes region have the glaciers to thank - the earth there is still "rebounding" from having been smushed by glaciers during the last ice age. ("Smushed" isn't actually a geological term, but it should be.)