Earth’s tallest mountain, Mt. Everest, doesn’t even make the top 10 among tall mountains in our solar system. That pack is led by Mars’ Olympus Mons, which is over 4 times higher than Everest and takes up an area about the size of Arizona.
On Earth, mountains can form in one of three ways: Volcanoes, fault-block mountains, in which one tectonic plate is being pushed under another, or fold mountains, where two tectonic plates are pushed up as they collide.
As mountains go, the oldest are often relatively small after eons of natural erosion. The oldest known mountains on Earth, the Makhonjwa Mountains in South Africa, reach only 1,800 meters above sea level (compared to Everest’s 8,850), but are 3.6 billion years old.
Because so many mountains are in the ocean, measuring mountains requires a distinction of tallest vs. highest. Mt. Everest may reach closest to the sky, but it is not the tallest. Hawai’i’s Mauna Kea is nearly a kilometer taller when measured from its base, which is far under the Pacific Ocean.
Because they can act as ramps for air masses, moisture, and snow, mountains can create their own weather. This is one reason you often see clouds at the tops of mountains, but nowhere else around.
Unsurprisingly, mountains play a big role in mythology and religion, and there are currently at least 66 “sacred” mountains in the world.
The longest terrestrial mountain range on earth is the Andes mountains, but under the sea lies most of the longest range on the planet. At over 40,000 miles long, the mid-ocean ridge runs around most of the globe.