Columnar jointing is a pattern of cracking in rocks that forms slender columns, typically six-sided. Jointing occurs when lava or magma comes into contact with a cool, flat surface. After the lava solidifies, it cools and shrinks, causing cracks to form perpendicular to the cool surface. In lava flows, cooling progresses from the top down (where the flow is in contact with air or water), forming regular columns. In Grand Canyon, the rapid cooling by river water would be the main cause for these incredible formations.
In 1869 J.W Powell describe it as “Just imagine a river of molten rock running down into a river of melted snow……What a seething and boiling of the waters; what clouds of steam rolled into the heavens” …. that truly does give you quite the visual.
Although Mars is quite different from Earth in many ways—smaller, colder, drier, and hostile to life—in some respects the two worlds are quite similar. Volcanoes shaped the surface of both planets, and a distinctive feature of volcanism (columnar jointing) was recently found on the surface of Mars! Wow, now doesn’t that really makes you wonder ?
Reference: Milazzo, M.P., Keszthelyi, L.P., Jaeger, W.L. Rosiek, M., Mattson, S., Verba, C., Beyer, R.A., Geissler, P.E., McEwen, A.S., and the HiRISE Team. (2009) Discovery of columnar jointing on Mars. Geology. 37(2), 171–174.