The stability of Olympus Mons, the largest volcano in our solar system, is primarily due to the difference in gravity and tectonic activity between Mars and Earth. On Mars, the surface gravity is only about 38 percent of Earth's gravity. This lower gravitational pull reduces the downward pressure exerted by the mountain's massive bulk, allowing the crust to support a much larger structure before reaching its breaking point.
Furthermore, Mars lacks plate tectonics. On Earth, moving tectonic plates often create mountain ranges through collisions, but they also cause volcanic activity to move geographically. On Mars, the crust remains stationary. This allows a single hotspot to vent magma in the exact same location for billions of years, building an incredibly wide and tall shield volcano through successive lava flows. Because the crust is thick and stable, it can support the massive weight of the accumulated basaltic layers without the widespread subduction or folding seen on Earth.
For more detailed scientific data regarding Martian geology, you can visit the official NASA website at https://science.nasa.gov.
