a process in which new ocean floor is created as molten material from the earth's mantle rises in margins between plates or ridges and spreads out.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
sea floor spreading
Sea floor spreading is making the Atlantic Ocean wider by a few inches each year.
The New Dictionary of Cultural Literacy, Third Edition Copyright © 2005 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.