Geologists have long-debated about when plate tectonics started on the planet. One of the key indicators has been whether or not fragments of oceanic crust, generated at sea-floor spreading centers, are preserved in the planet’s oldest crust. New research integrating what has been learned about the variations in modern sea floor spreading environments with the geological record of the oldest preserved crust on Earth Geologists have long-debated about when plate tectonics started on the planet. One of the key indicators has been whether or not fragments of oceanic crust, generated at sea-floor spreading centers, are preserved in the planet’s oldest crust. New research integrating what has been learned about the variations in modern sea floor spreading environments with the geological record of the oldest preserved crust on Earth