The United States has the world's largest economy by nominal GDP, followed by China.

The Great Rift Valley in Africa may eventually split the continent in two, forming a new ocean in millions of years.

The Amazon River is one of the longest rivers in the world.

The CN Tower in Toronto was once the tallest free-standing structure.

Some deserts were once oceans.

The Caspian Sea is technically the world's largest lake, covering 371,000 square kilometers.

The Sahara Desert is expanding southward at a rate of about 48 kilometers per year due to desertification.

The Nile is generally considered the world's longest river, but some measurements put the Amazon ahead depending on source point.

The Sahara Desert experiences dramatic temperature changes.