Mt. Everest might be the tallest mountain on Earth, but it's nothing compared to the tallest volcanic mountain in the solar system, Olympus Mons on our red cousin Mars.

John Brady at Astronomy Central shows, in the image below, what this gargantuan feature would look like if it were on the continent of North America — it would completely cover the state of Arizona!

John Brady Named for Mt. Olympus — the highest mountain in Greece — Olympus Mons towers 16 miles above the Martian surface — three times taller than Mt. Everest. This mountain is also the largest volcano in the solar system with a caldera at its summit that is 53 miles across. Here's what that looks like compared to Everest:

Olympus Mons on Mars, the tallest planetary mountain in the Solar System, compared to Mount Everest and Mauna Kea on Earth. Resident Mario on Wikimedia Commons The caldera is easily visible as the small, central circle in the NASA picture below of Olympus Mons, the zit-looking mound in the upper center, which Brady used for his comparison image.

NASA With a diameter of 375 miles, Olympus Mons is part of the largest volcanic region on Mars called the Tharsis Montes. The region spans 2,500 miles across the surface of Mars and contains 12 large volcanoes that are up to 100 times larger than any volcanoes on Earth.

Like the volcanoes that formed the Hawaiian islands, Olympus Mons is a shield volcano, which is named after its shape, which resembles a warrior's shield. Shield volcanoes erupt lava that flows more easily than lava from some other eruptions, which means the lava travels a further distance before cooling and hardening giving shield volcanoes their distinctive shape, which you can clearly see in the NASA image below:

Olympus Mons on Mars as viewed from Viking 1 in 1978. Image by NASA, modifications by Seddon Eruptions, which could last for hundreds of years at a time, and subsequent lava flows built a ridge up around the central peak of Olympus Mons, shown in the computer-generated view below. This ridge is estimated to be 6 miles high — higher than the tallest point on Mt. Everest, which is 5.5 miles above sea level.

NASA/MOLA Science Team/ O. de Goursac, Adrian Lark Scientists estimate that the last time Olympus Mons erupted lava onto the Martian surface was between 20 and 200 million years ago — around the same time that dinosaurs roamed the Earth

While some scientists think that this last eruption on Olympus Mons marks the last breath of volcanic activity on Mars, others suggest this monstrous volcano is still active despite being dormant for millions of years. A scary thought when you consider the volcano's colossal size.

Olympus Mons is the largest planetary mountain in the solar system, but there's a mountain on the asteroid, Vesta, that is the largest mountain around. Called Rheasilvia, the mountain is a mere 315 feet higher than Olympus Mons.