Olympus Mons on Mars and Mount Everest on Earth represent the colossal peaks of their respective worlds, yet their comparison highlights a dramatic difference in planetary scale. The Martian giant is the largest known volcano and mountain in the entire solar system, while Everest holds the title of the highest point above sea level on our home planet. Examining how these two monumental structures stack up against each other provides a window into the distinct evolutionary paths of Earth and Mars.
The Vertical Difference
The most direct comparison between the two peaks lies in their sheer vertical height. Mount Everest’s summit reaches an elevation of approximately 8.8 kilometers (5.5 miles) above sea level. In contrast, Olympus Mons towers approximately 21.9 kilometers (13.6 miles) above the Martian planetary datum, which serves as the equivalent of sea level on the waterless Red Planet.
This vast difference means the Martian mountain is roughly two and a half times taller than Earth’s highest peak. If Olympus Mons were situated on Earth, its summit would extend far beyond the altitude where the atmosphere supports weather systems. The peak also rises about 26 kilometers (16 miles) above the plains surrounding its base.
Understanding the Footprint
The height differential only tells part of the story, as the horizontal scale, or footprint, of Olympus Mons is immense. The Martian shield volcano stretches across a basal diameter of approximately 600 kilometers (370 miles), covering a total area of about 300,000 square kilometers (120,000 square miles).
To visualize this scale, the base of Olympus Mons is comparable to the entire state of Arizona or the country of Poland. The sheer volume of Olympus Mons is estimated to be about 100 times greater than Mauna Loa, the largest volcano on Earth by volume. This difference highlights that Everest is a sharp, folded peak created by plate collision, while Olympus Mons is a massive, gently sloping shield built by fluid lava flows.
Why the Discrepancy?
The fundamental reasons for this extreme size difference are rooted in the physical and geological characteristics of the two planets. Mars possesses a surface gravity that is only about one-third of Earth’s, which is a major factor in allowing structures to grow so tall. Lower gravity places less stress on the rock materials, meaning a mountain can reach a much greater height before its own weight causes it to collapse.
Another element is the absence of mobile plate tectonics on Mars. On Earth, tectonic plate movement continually shifts the crust away from volcanic hotspots, leading to the formation of chains of smaller volcanoes, such as the Hawaiian Islands. Because the Martian crust remained stationary over a magma plume for billions of years, the hotspot continuously fed lava to the same location. This sustained eruption process allowed Olympus Mons to grow into a massive shield volcano.
Finally, the rate of erosion on the two worlds plays a role in preserving the Martian giant. Earth’s mountains are constantly being worn down by wind, water, and ice. Mars, with its thin atmosphere and lack of liquid surface water, has experienced significantly less erosion over the eons. This minimal weathering has allowed the massive structure of Olympus Mons to remain largely intact.