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**What is Tectonic Shift?** Tectonic shift is the **movement of the plates** that make up Earth’s crust.  Map of tectonic plates from National Park Service; source: http://www.nature.nps.gov/geology/education/education_graphics.cfm (Modified by NPS from: R. J. Lillie. 2005. Parks and Plates.)*The Earth is made up of roughly a dozen major plates and several minor plates.* **Did you know?** *Measuring  the motion of tectonic plates is part of the science of geodesy. To define the  shape of the Earth, NOAA’s National Geodetic Survey, part of the National Ocean  Service, uses a variety of techniques to measure the planet’s rate of rotation,  its plate motion, and the ways that gravity affects certain scientific  processes. Learn more: What is Geodesy?*
 The  Earth is in a constant state of change. Earth’s crust, called the  lithosphere, consists of 15 to 20 moving tectonic plates. The plates can be  thought of like pieces of a cracked shell that rest on the hot, molten rock of  Earth’s mantle and fit snugly against one another. The heat from radioactive  processes within the planet’s interior causes the plates to move, sometimes  toward and sometimes away from each other. This movement is called plate  motion, or tectonic shift. Our  planet looks very different from the way it did 250 million years ago, when there  was only one continent, called *Pangaea,* and one ocean, called *Panthalassa.* As  Earth’s mantle heated and cooled over many millennia, the outer crust broke up  and commenced the plate motion that continues today. The  huge continent eventually broke apart, creating new and ever-changing land  masses and oceans. Have you ever noticed how the east coast of South America looks  like it would fit neatly into the west coast of Africa? That’s because it did,  millions of years before tectonic shift separated the two great continents. Earth’s  land masses move toward and away from each other at an average rate of about 1.5 centimeters (0.6  inches) a year. That’s about the rate that human toenails grow! Some  regions, such as coastal California, move quite fast in geological terms — almost  5 centimeters (two inches) a year — relative to the more stable interior of the  continental United States. At the “seams” where tectonic plates come in  contact, the crustal rocks may grind violently against each other, causing  earthquakes and volcano eruptions. The relatively fast movement of the tectonic  plates under California explains the frequent earthquakes that occur there.
 More **Information** National Geodetic Survey What is geodesy? What is the geoid? "Coping with Tectonic Shift," The American Surveyor   Get **Social** Social
  **Last updated:** 01/18/24 **Author:** NOAA How to cite this article Contact Us


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