Our friend, mentor and newly appointed President gave the TVGS Christmas lecture, held at the Crown Inn Martley, December 9th 2013. Paul’s topic was Volcanoes in the Solar System, and a crowd of over 50 squeezed not too comfortably into the room arranged for the evening. Using his now familiar overhead projector with acetates and later a slide projector—slides NOT Power Point, note, Paul took us on an astonishing journey through our Solar System. The advent of space exploration has revealed a tremendous variety of volcanoes and volcanic effects that were not dreamt of previously.

We are familiar with volcanoes here on Earth, fast flowing Hawaiian lava from low, broad shield volcanoes to the thicker explosive lavas and pyroclastic flows from towering crags e.g. Mt St Helen’s, Vesuvius. We also fully accept how plate tectonics affects the shapes of the continents and that plate boundaries provide a focus for earthquakes and eruptions.

We have always been able to see many craters on our moon, thousands of them, but whether all impact or some volcanic was not clear. Exploration now shows, Paul explained, that past heavy impacts pierced and shattered surface rocks making a way for magma to flow to the surface from the then (2500Ma) molten interior. This heavier basaltic material spread out leaving what we now call mare or seas; satellites reveal that these smoother, darker areas have a higher gravity than their surrounds in support of the above theory.

Venus is cloaked in thick dense cloud, and is hot to the point of making rocks themselves semi molten and sticky. Radar survey show a tremendous amount of volcanic activity has and possibly is still occurring. Strange circular, depressed areas, ‘pancake domes’ and more normal volcanoes with smoothed flanks are a result of the extreme temperatures and pressures on the planet.

Mars has very apparent evidence of vulcanism, strangely grouped in one area with possibly six volcanoes still active. Owing to low gravity, a very thin atmosphere and the absence of plate tectonics, eruptions enable huge, high mountains to build and the ejection of erupted materials well above the atmosphere into space. Olympus Mons, the monster of the bunch, is around 79000 feet high, dwarfing anything here on Earth. Other huge Mars features belie volcanic activity, in particular a huge canyon thousands of miles long, deeper than the Grand Canyon—thought to be collapsed magma chambers.

Beyond Mars to the gas giants of Jupiter, Saturn, Uranus, Neptune with their many and varied moons. These too, in a number of instances, display volcanic features, though not as we know them (Jim). Gripped by the gigantic gravity of their parent, moons are squeezed and stretched, with consequent heating and resultant volcanic activity, often exceptionally violent and continuous. There are sulphur volcanoes on Io (Jupiter), ethane seas and methane rain and rivers on Titan (Saturn), and even nitrogen volcanoes on Triton (Neptune), as distances from the sun increase and local temperatures and conditions favour totally foreign and ‘out of this world’ (literally) forms of vulcanism.

Thank you, Paul, for taking us with you on your space ship to explore our neighbours, opening our minds in the process to the wonderful and strange processes that take place in our Solar System. We look forward to your Christmas lecture next year and wish all TVGS friends a very happy Xmas season and educative New Year.