The Earth's mantle lies between the crust and core.

The tallest mountain above sea level is Mount Everest.

Angel Falls in Venezuela is the world's highest uninterrupted waterfall at 979 meters.

The Earth is slightly flattened at the poles.

The city of Istanbul spans two continents — Europe and Asia.

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

The Pleistocene epoch included repeated glacial cycles.

The Nile Delta is sinking — it's being weighed down by sediment and eroded by rising seas.

The Palm Islands in Dubai were constructed using land reclamation techniques.