Bill Clinton visited both the Grand Canyon (in 2000) and Yellowstone (in 1995). President Clinton stayed in the Mary Colter Suite of the Grand Canyon's El Tovar and had lunch at Yellowstone's Old Faithful Inn. President Clinton and the First Lady also took a stroll around Old Faithful Geyser.
Exploding Water in the Microwave. It's practically an urban legend: a man heats water in the microwave for a cup of instant coffee. While taking the cup out of the microwave, he notices the water doesn't have any bubbles...at which point, the water boils up and explodes, giving him burns on his face and hands.
You may see some pumice stones that have broken off due to erosion by the sea. Amazingly, they will actually float on the water for some time. Dense stones, of course, do not float on water. But because pumice is full of air bubbles, it is less dense than water.