The Pacific Ring of Fire hosts 90% of the world's earthquakes and 75% of its active volcanoes.

The Sahara desert was a green savanna as recently as 5,000 years ago.

Iceland sits directly on the Mid-Atlantic Ridge and is actually spreading by 2.5 cm per year as two tectonic plates diverge.

The Earth's crust varies in thickness beneath continents and oceans.

The Angel Falls in Venezuela is the world's highest uninterrupted waterfall at 3,212 feet.

In Switzerland, it is illegal to own just one guinea pig — they are social animals and must have a companion.

Mount Everest lies on the border between Nepal and China.

The longest mountain range in the world is the Andes.

The United States purchased Florida from Spain in 1819.