Volcanoes eject almost a cubic mile of material into the atmosphere each year, on average. At this rapid rate, about 10 times the entire volume of Earth’s sedimentary rock should be produced in 4.5-billion years. Actually, only about 25% of Earth’s sediments are of volcanic origin, and much greater volcanic activity existed in the past. No means have been proposed for removing or transforming all the missing volcanic sediments. Therefore, Earth’s sediments seem to be much younger than 4.5-billion years.a