Dinosaurs And Spark Plugs

Did you know that the firing end of your car's spark plugs and the extinction of dinosaurs are linked by the same metal--iridium? A clue to the extinction of the dinosaurs was found in a layer of rock laid down at the time of the extinction of the dinosaurs, 65.5 million years ago, that contained a very high concentration of iridium. Iridium occurs in high concentrations in asteroids. The layer must have been laid down by dust settling over the entire planet after a very large asteroid impact. Iridium is one of the nine least abundant elements in Earth's crust, gold is 40 times more abundant, platinum is 10 times more abundant, and silver and mercury are 80 times more abundant. Iridium is found in high enough concentrations for mining in two types of geologic locations: igneous deposits (crustal intrusions from below, iridium is heavy and sank into the central layers of the molten early Earth), and impact craters. The high melting point, hardness, and corrosion resistance of iridium make it the perfect metal for the spark point of spark plugs.