On this day in 79 A.D. Mount Vesuvius erupts and buries the towns of Pompeii and Herculaneum in tons of ash and cinders. Thought to be a dormant volcano, Vesuvius was where Spartacus went after he escaped slavery. The towns were buried so quickly that many of the inhabitants didn't have time to escape. Much of Pompeii was preserved, and when archaeologists excavated the site, they found casts of the people buried by the volcanic ash.
On this day in 1814 British troops under the command of Robert Ross capture and burn all the federal buildings of Washington D.C. The United States army was caught completely off guard when British ships showed up on the Chesapeake a week prior. The British encountered little resistance and the capitol was forced to evacuate. What wasn't burned was destroyed by a hurricane that arrived the next night.
On this day in 1873 William Henry Jackson captured the first picture of the Mount of the Holy Cross, proving its existence. It had long been rumored that a perfect cross made out of snow was in the Rocky Mountains of Colorado. Jackson set out to find it and prove it was real. It is a natural phenomena where two eroded gullies in the hills intersect at a 90 degree angle. The snow inside these is hidden from the sun and lasts long after the surrounding snow melts away.
On this day in 2006 Pluto was demoted from a planet to a dwarf planed by the scientific community at large. Because of it's irregular orbit and its small size, Pluto was just a bit more odd than its fellow planets. At times it is closer to the sun than Neptune, and it dips well below and well above the other planets in its orbital plane. So we have 8 planets again.