Volcanoes on Venus, distribution and size

How many volcanoes on Venus?

Venus was very volcanically active 200 to 500 million years ago. Images obtained by various probes sent to Venus allowed us to see many impact craters of average size, and even distribution, which implies that the surface is relatively young. There are no small craters on Venus. On the maps that the Magellan probe managed to complete we see:

thousands of volcanoes of at least 10km diameter
274 volcanoes between 20 and 100km in diameter
156 larger than 100 km

There are craters of over 1.5 km diameter of which the largest attains 280 km.

Protected by the atmosphere of Venus

The dense atmosphere of the planet burns most small asteroids and comets up and only large objects hit the ground: there are fewer than 1000 impact craters on Venus. The dominant theory with planetologists is that a ‘recent’ increase in internal activity with large scales eruptions resurfaced the majority of the planet.

In fact their amazing state of preservation is perhaps misleading: there is little erosion on Venus because there is no rain and the thick atmosphere of carbonic gas plays more of a protective role than that of a destructive agent. Markings that seem recent could in fact be tens or even thousands of millions of years old.

Are venus volcanoes still active on Venus?

Thanks to Venus probes we see lava domes (roughly circular mound resulting from the slow eruption of lava) of 15 to 90km in diameter, plateaus, and huge hills, of which the tallest is Mount Maxwell that is 11 000 m high. We also see "coronae" – strange circles of wrinkles and cracks in the crust, of which the largest is 2 600 km.

However, in 3 years of observations, the Magellan probe never witnessed an eruption on Venus, as if the volcanoes were currently dormant.

The impact craters are spread in a random way across the entire surface of Venus. Most of them (white dots) are unchanged and are concentrated in areas like ‘Aphrodite Terra’. Regions of low crater density (blue zones) are often areas of raised plateaus. Regions of higher density generally correspond to the plains. Credits NASA.

The terrain of Venus is mostly made up of plains (blue). In the middle of these plains there are areas of deformation such as tesserae (pink), volcanic structures such as coronae (peach), lava flows (red) and different sizes of volcano (orange). Volcanoes are not concentrated in chains as on Earth, indicating the lack of tectonic plates. Credits NASA.

This geological map indicates different types of terrain and their respective ages, deduced from crater density. Volcanoes and crowns (coronae) seem to be focused on younger equatorial rift zones (blue). The tesserae, plains and peaks are older (yellow). Credit: NASA.