Life and Earth Sciences - Baccalaureate S - Lesson - The production and recycling of the lithosphere

Production and Disappearance of Oceanic Lithosphere
📌 Oceanic lithosphere is produced at ridge zones where peridotite partially melts to form basalts and gabbros, which constitute oceanic crust.
🌊 Oceanic lithosphere disappears at subduction zones, where it plunges beneath either continental or other oceanic lithosphere.
🔄 Complete recycling occurs; the oceanic lithosphere produced at ridges disappears entirely into the mantle at subduction zones.

Production and Disappearance of Continental Lithosphere
🌋 Continental lithosphere is produced at subduction zones through the partial melting of overlying peridotites, triggered by dehydration of the subducting slab, leading to the formation of granitic rocks.
⛰️ The primary process for the disappearance (or removal from the surface) of continental lithosphere is erosion (mechanical and chemical weathering) acting on positive reliefs like mountain chains.
📉 Erosion removes material, reducing the altitude of mountain chains; isostatic compensation causes the underlying crystal root to rise progressively until the crust flattens to about 30 km thickness.
⏳ Unlike oceanic lithosphere, continental lithosphere is only partially recycled; material eroded from relief can be transported and deposited, and only mobilized continental crust can re-enter subduction zones, explaining the existence of continental crust over 4 billion years old.

Key Points & Insights
➡️ Oceanic lithosphere undergoes total recycling: created at ridges and destroyed completely at subduction zones.
➡️ Continental lithosphere is created at subduction zones but is only partially recycled via erosion processes.
➡️ Continental crust can survive for extremely long periods (e.g., $>4$ billion years) because erosion only removes surface material, leaving the bulk relatively intact unless remobilized.

📸 Video summarized with SummaryTube.com on Jan 07, 2026, 06:41 UTC