Mars, the planet nearest Earth, is a world of dramatic contrasts, featuring the deepest canyons and the largest impact basins in the solar system. These immense elevations are a primary feature of Mars’s topography, distinguishing its surface from our own planet’s more familiar landscapes. Martian mountains exist on a colossal, geological scale, resulting from unique physical and geological forces at work on this distant world.
Answering the Question: Martian Scale
The most prominent mountainous region on Mars is the Tharsis bulge, a vast, elevated plateau situated near the planet’s equator. This immense dome of uplifted crust is approximately 5,000 kilometers across, covering up to 25% of the Martian surface. The region’s average elevation is already about 7 kilometers higher than the rest of the planet, forming a massive pedestal for the largest mountains.
The mountains that rise from this bulge are fundamentally different from Earth’s sharp, jagged peaks. Martian mountains, particularly the colossal volcanoes, are characterized by extremely broad bases and gentle slopes. Their immense size means that if one were standing on the flank of one of these peaks, the summit would often be invisible beyond the horizon. This gentle topography is a signature of the unique geological processes that created these structures.
Olympus Mons: The Solar System’s Giant
The most famous example of Martian topography is Olympus Mons, the largest known volcano in the entire solar system. Situated just off the western edge of the Tharsis region, it utterly dwarfs any mountain on Earth. At its highest point, the volcano reaches an altitude of over 21.9 kilometers, making it approximately three times taller than Mount Everest’s height above sea level.
Olympus Mons is a shield volcano, built up by numerous flows of highly fluid, basaltic lava over billions of years. Its base spans a phenomenal 600 kilometers, an area roughly equivalent to the state of Arizona. At the summit, a complex, nested caldera system forms a depression up to 85 kilometers wide. The mountain is also defined by an immense outward-facing cliff, or escarpment, that can reach a height of up to 8 kilometers.
Geological Processes of Martian Mountain Building
The creation of Mars’s colossal mountains is primarily attributed to a massive, long-lived style of volcanism. Unlike Earth, Mars lacks active plate tectonics that constantly shift the crust over underlying magma hotspots. This absence allowed a stationary magma plume to feed lava to the same spot on the surface for hundreds of millions or even billions of years.
This continuous, localized eruption allowed the shield volcanoes of the Tharsis region to grow to staggering heights and widths, accumulating enormous volumes of material. Some smaller mountainous terrains are remnants of ancient, massive impact basin rims rather than volcanic structures. Other minor features, known as inverted relief, formed when lava flows or sediment filled low-lying stream beds, and the surrounding, softer material was later eroded away.
Contrasting Martian and Terrestrial Peaks
The fundamental differences between Martian and terrestrial mountains stem from gravity and plate tectonics. Mars’s surface gravity is only about 38% of Earth’s, which allows volcanic structures to grow much taller before their sheer weight causes them to collapse. This lower gravitational force enables the existence of a 22-kilometer-high peak like Olympus Mons.
Earth’s highest ranges, such as the Himalayas, are formed by the slow, forceful collision of continental plates, which folds and thrusts rock layers upward. These folded mountains are sharp and steep, but their growth is limited by the ongoing movement of the tectonic plates. Martian mountains, in contrast, are almost entirely the result of singular, continuous volcanic construction at a stationary point. This explains why the gentle, broad profile of the shield volcano is the dominant Martian mountain form.