Similar to our pockmarked Moon, Earth was once covered with numerous meteorite impact scars. In contrast to our living planet, the Moon has been stone-dead for a long time. Even today, giant impact basins several hundred kilometres across, preserved over about 4 billion years, are exposed on the lunar surface. These large craters are, in turn, superimposed by thousands of smaller and younger impact craters struck since that early time of intense cosmic bombardment. Many of the impact basins are filled with dark volcanic basalts visible as the black fillings of the lunar maria that together form the “Man in the Moon”.
But we don’t have to go that far; 188 “fossil” meteorite impact craters are currently known on Earth – 29 in Australia, 22 in Asia, 48 in Europe, 19 in Africa, 60 in North America and 10 in South America. Earth is a geologically active planet on which Mother Nature knows a multitude of ways to recycle rocks and reshape the outer layer of crust on which we live.
Various processes associated with plate tectonics can erase impact craters from the Earth’s surface over time. Erosion is a seemingly never-ending process that, slowly but surely, grinds down every impact crater. Some deeply eroded craters are barely visible as such, and can only be recognised by the study of rocks that were crushed, shocked and even melted as indirect geologic evidence...
