edict when this will transpire. (Learn About Precambrian Time) Cheng’s new paper uses mathematical models to estimate how fast the mantle is cooling, based on what we know about the intensity of the planet’s magmatic activity from three billion years ago to now. That, he says, gives us a first-order estimate of when plate tectonics will end. On the Path to Stillness Regardless of the precision of this figure, plate tectonics will inevitably perish, says Ken Hudnut , a research geophysicist working with the United States Geological Survey. When that day arrives, it “may well be the end of the world as we know it.” SCIENCE Here's why Earth is closer to the sun on January 3 SCIENCE Is gluten really that bad for you? SCIENCE What happens to your brain when you take a break from social media Earth would likely enter a single lid regime , a completed jigsaw of titanic slabs that will no longer drift or sink. Mountain building will stop, but Earth will still have an atmosphere, so erosion by wind and waves will shave down the mighty peaks to hilly plateaus. Eventually, much of the flattened continents will be underwater. Subduction zones will no longer exist, so while earthquakes will still happen every now and then, truly earthshattering events above magnitude 7 or so will be consigned to history. At the same time, much of the world’s explosive volcanism would be extinguished—although volcanoes would not be entirely snuffed out. Mars, a world of failed plate tectonics, did manage to forge some impressive volcanic features, including Olympus Mons , the largest volcano in the solar system. Without moving plates, a long-lived upwelling mantle plume focused plenty of crustal melting on that one single spot. While the mantle of future Earth remains warm enough to convect and partially melt, we would get similar but scattered stationary hot spots of plume-driven volcanism. We would never get anything as large as Olympus Mons on Earth, as our gravitational field is too stro