Britannica
Sources used in this answer
Why are Middle Jurassic oceanic crust and sediments often the oldest rocks remaining on the deep seafloor?
Created from Britannica articles
using AI.
AI can make mistakes, so verify using Britannica articles.
Jurassic Period
Distribution of landmasses, mountainous regions, shallow seas, and deep ocean basins during the late Jurassic Period. Included in the paleogeographic reconstruction are the locations of the interval's subduction zones.
Middle Jurassic oceanic crust and sediments are generally the oldest materials remaining on the deep seafloor because of the continuous process of plate tectonics.1
New seafloor is constantly generated at mid-oceanic ridges through seafloor spreading. Over time, this crust moves laterally away from the ridges and eventually reaches subduction zones, where it is forced downward into the Earth's mantle and destroyed. Because older, denser oceanic crust is consistently consumed in these trenches, the vast majority of the seafloor is relatively young; consequently, only remnants from the Middle Jurassic and later periods typically survive on the ocean floor today.2314