This document summarizes information about the life cycle of oceanic crust and spreading ridges. It discusses that oceanic crust is formed at mid-ocean ridges as molten rock from the mantle reaches the seafloor and solidifies. Oceanic crust is then destroyed as it is subducted at convergent plate boundaries. The document also provides information about ophiolites, which are sections of oceanic crust and upper mantle rock that have been uplifted and exposed on land.

1. “LIFE CYCLE OF OCEANIC CRUST, SPREADING
RIDGES & OPHIOLITES”

2. PRESENTED BY : SARDAR OBAID-UR-REHMAN
ENROLLMENT # : 46
SEMESTER : 7TH (MORNING)
“GEO-TECTONICS”

3. WHAT IS OCEANIC CRUST ?
 Oeanic crust, the outermost layer of Earth’s lithosphere that is found under the oceans and
formed at spreading centers on oceanic ridges, which occur at divergent plate boundaries.
1. Oceanic crust is about 6 km (4 miles) thick.
2. The topmost layer, about 500 meters (1,650 feet) thick.
3. It is thinner, denser, younger.
4. Oceanic crust is destroyed in subduction zones.

4. EXPLORING THE LAYERS IN OCEANIC CRUST

5. “LIFE CYCLE OF OCEANIC CRUST + SPREADING
RIDGES”

6. WILSON CYCLE

7. WHAT IS SPREADING RIDGES ?
 A spreading ridge is the fracture zone along the ocean bottom where molten mantle material
comes to the surface, thus creating new crust. This fracture can be seen beneath the ocean as
a line of ridge that form as molten rock reaches the ocean bottom and solidifies.

8. HOW OCEANIC CRUST IS FORMED AND DESTROYED?
 Oceanic crust is formed at mid- oceanic ridges, whereas oceanic crust is destroyed at sub
duction zone.

9. INTERESTING INFORMATION
 The speed of crust formation varies from ridge to ridge: Some fast-spreading ridges produce
up to 6 inches (15 centimeters) of new crust per year, while slower-spreading ridges creep
along at just 2 inches (5 cm) per year.

10. FORMATION & DESTRUCTION OF OCEANIC CRUST

11. “OPHIOLITES”

12. HISTORY OF OPHIOLITE
 “Ophio” is a Greek word which was used for “SNAKE”, Lite means “STONE” and it is also
derived from Greek word “Lithos”.
 The name is given because ophiolites have similarity in colour and texture with snakes, some
greenish colour.

13. DEFINITION
An ophiolite is a section of the earth’s oceanic crust and the under lying upper mantle that has
been uplifted or emplaced to be exposed within continental crustal rocks.

14. LITHOLOGY OF OPHIOLITE

15. SIMILARITY B/W OCEANIC CRUST & OPHIOLITES

16. OPHIOLITE LOCALITIES

17. EURASIAN BLOCK OPHIOLITES
 Dargai.
 Mingora – Bajaware.
 Chilas.

18. EXISTENCE OF OPHIOLITE WORLDWIDE

19. THE END
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