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Paleozoic and Mesozoic Seas | CK-12 Foundation Skip Navigation
10.17: Paleozoic and Mesozoic Seas  Difficulty Level: Basic
Created by: CK-12 Practice Paleozoic and Mesozoic Seas Practice
Now  Do you like the beach? If so, the Paleozoic may be for you!
If we were living right now at the time of a marine
transgression, there would be a lot more beach. Surf's up!
Marine Transgressions and Regressions  Sea level rises and
falls. During the Paleozoic and Mesozoic, the seas rose over the
continents. This is called a marine transgression . During a
marine regression , the sea level retreats. The Paleozoic had
four complete cycles of marine transgressions and regressions.
The Mesozoic had two ( Figure below ).  Six marine
transgressions and regressions have occurred during the
Phanerozoic.  What makes sea level rise? There are two
possibilities: Either the land sinks or the water level rises.
Tectonic processes can cause the land to sink. Melting glaciers