World of geology

Tony Waltham (UK) This article accompanies a book review of Tony Waltham’s book, The World of Geology. The text is broadly taken from the book itself. The world of geology is the world as we know it, that we see and that we live on. It is all about the evolution of the Earth’s crust, the nearly rigid layer less than 100km thick that is the outer shell of our evolving planet. This crust is broken into a few dozen large and small tectonic plates, which move around at rates of a few centimetres a year. Originally known as continental drift when it was first recognised in 1912, this geological activity has been referred to as plate tectonics since its processes began to be properly understood during the 1960s. A large part of the Earth’s crust is the oceanic floor. The basaltic rock of the slowly moving oceanic plates is continuously being created along plate boundaries that are divergent, and destroyed along those that are convergent. These are the major processes of plate tectonics that keep Planet Earth evolving and alive. The oceanic basalts are similar to those in some types of volcano, but otherwise they remain largely unseen beneath the cold, dark and minimally explored waters of the ocean depths. The second part of the Earth’s crust is the incomplete upper layer, largely of granitic composition, that forms the continents. Along with the submerged edges known as the continental shelves, these occupy about one third of our planet’s surface. … Read More