Mars has incredibly big and tall geological formations than those on the Earth. Moreover, the biggest and tallest volcano of the entire solar system is found on Mars: it is Olympus Mons, reaching a height of almost 23 kilometres. This volcano is found in a region of Mars named Tharsis Montes, where we also find other volcanos with enormous dimensions.
Characteristics of Olympus Mons
Olympus Mons is the youngest volcano on Mars. It was formed about 1,8 billion years ago. Even if the highest peak of this volcano elevates to a height of nearly 23 kilometres over the Martian surface, the volcano is situated in a depression of about 2 kilometres in depth. So, Olympus Mons is nearly three times higher than the highest peak on the Earth, Mount Everest, the latter arriving at a height of about 9 kilometres above sea level, exactly 8,848 metres.
This volcano of enormous dimensions is bordered by some vertical cliffs with a height of 6 kilometres. Comparing the size of this volcano with those on the Earth, we can appreciate that the cliffs that border it, are higher than many mountains and volcanos on Earth.
At the peak of Olympus Mons is found a volcanic caldera of enormous dimensions. This caldera is 85 kilometres long, 60 kilometres wide, and has a depth of 3 kilometres. The base of this volcano has a diameter of 620 kilometres, approximately the same size that the state of Arizona, in the United States.
Size and shape
The enormous base of this volcano gives it an area, at its base, of approximately 283,000 km2. If Mount Olympus was in Europe, it would cover a great part of France. Such dimensions are difficult to imagine. In fact, the dimensions of this volcano are so great that if we were on the Martian surface we wouldn’t be able to see its shape completely. Even if we moved away from it, we would only see a wall that resembling a huge cliff.
Similarly, we wouldn’t be able to see it completely if we were at its peak. From its highest point, we would only see part of its slope. We wouldn’t get to see the end as it would blend with the horizon. Therefore, the only way to observe Olympus Mons in its totality is from space.
In comparison, the biggest volcano on Earth is the Mauna Kea, one of the volcanos in the Hawaii islands, with a height of about 10 kilometres (a great part of it is found underwater) and 120 kilometres of base. Olympus Mons contains about 4 million cubic kilometres of material, and its volume is approximately 100 times bigger than the one of Mauna Kea.
Olympus Mons is a shield volcano. This type of volcanos are characterised by being wider and taller, and having a rounded and flat shape. Rather than expelling violently rocks, ash or lava, shield volcanos are created by lava that flows slowly down by its sides. As a result, the volcano has the before mentioned characteristics, with a slope of only a 5%.
The formation of a giant
Why would a so large volcano form on Mars but not on Earth? The answer to this phenomenon has to do with tectonic plates, or, rather, of its absence.
Under the surface, there are some areas where temperatures are very elevated. These zones are called “hot spots”. In them, great quantities of magma are generated. On the Earth, tectonic plates move above these hot spots, giving birth to new volcanos. In fact, the Hawaii islands are the result of the northeast movement of the Pacific plate over a stationary hot spot that produces lava. As the plate moves above this hot spot, new volcanos are formed and the existent ones extinguish. This makes the total volumes of lava to be distributed in many volcanos rather than in one and enormous volcano.
On Mars, where there aren’t tectonic plates, or at least they don’t move, lava is piled in many layers, to form a unique and enormous volcano. In 2004, the Mars Express probe, developed by the ESA (European Spatial Agency), detected that the fluxes of lava in the slopes of the volcano seemed to have an antiquity of only 2 million years, a very recent date in geologic terms. This could mean that this enormous volcano could still have a slight volcanic activity.