Mars does not have active lava flows on its surface today, but the planet has an extensive history of volcanism that has shaped much of its surface. Magma is the molten rock found beneath a planet’s surface, while lava is that material once it erupts. For billions of years, Mars experienced massive eruptions, leaving behind a geological record of solidified lava. Studying these ancient flows and colossal volcanoes is central to understanding the history and evolution of the red planet.
Widespread Evidence of Ancient Martian Lava Flows
The geological evidence of past lava activity on Mars is not limited to its towering volcanoes; vast plains of solidified lava cover significant portions of the Martian surface. These regions, particularly the Tharsis and Elysium provinces, show a history of extensive, low-viscosity flows that spread out over immense distances. The flows were predominantly basaltic in composition, similar to the fluid lava that forms the Hawaiian Islands on Earth.
The movement of this fluid lava formed long, narrow channels and subsurface conduits known as lava tubes, which are visible where their roofs have collapsed. Additionally, the cooling and contraction of the massive lava sheets created distinctive geological structures like wrinkle ridges. These ridges are folds in the crust that formed after the flows solidified and were subsequently pushed together. The sheer scale and volume of these ancient lava seas confirm that volcanism was a primary force in Martian geological history.
The Colossal Volcanic Structures
The most spectacular testament to Mars’ volcanic past is the existence of the Tharsis region’s immense shield volcanoes, which dwarf any found on Earth. Olympus Mons is the most famous example, standing approximately 22 kilometers (14 miles) high, making it nearly three times taller than Mount Everest above sea level and the tallest known mountain in the solar system. The base of the volcano is approximately 600 kilometers (370 miles) wide.
These volcanoes were able to grow to such colossal dimensions due to two primary factors unique to Mars. First, the planet lacks mobile tectonic plates; the Martian crust remained stationary over a magma hotspot for billions of years. This allowed lava to erupt repeatedly from the same fixed location, continually building the shield volcano higher and wider. Second, Mars’ lower surface gravity, about one-third of Earth’s, permitted the volcanic structures to reach greater heights before the material caused them to collapse. Olympus Mons is joined by three other enormous shield volcanoes—Arsia Mons, Pavonis Mons, and Ascraeus Mons—that collectively dominate the Tharsis Bulge.
The Current State of Martian Volcanism
While Mars is currently considered geologically dormant, meaning major eruptions have ceased, the vast majority of volcanic activity took place during the Hesperian and early Amazonian epochs, which ended billions of years ago. The planet’s smaller size, compared to Earth, meant that its internal heat dissipated much faster. This caused the deep mantle heat needed to fuel large-scale volcanism to diminish over time.
The question of complete extinction remains a subject of scientific discussion, especially concerning the Elysium Planitia region. Studies suggest that some lava flows may be geologically young, possibly occurring within the last million years. Furthermore, the now-retired NASA InSight lander detected numerous “marsquakes,” with a significant cluster originating from the Cerberus Fossae region. This seismic activity confirms that the planet’s interior is not entirely static, with residual processes potentially driven by deep-seated magmatism still occurring beneath the surface.