Oceanic crust is the uppermost layer of oceanic tectonic plates. It is formed from erupted mantle material at mid-ocean ridges and is composed primarily of mafic rocks. As the plates move away from the ridges, the oceanic crust spreads out. Eventually, the older oceanic crust subducts at convergent plate boundaries, where it is consumed and recycled into new magma. This completes the life cycle of oceanic crust, as new crust is continually generated at mid-ocean ridges to replace what is destroyed by subduction.

1. OCEANIC CRUST AND ITS LIFE
CYCLE

2. WHAT IS OCEANIC CRUST?
• OCEANIC CRUST IS THE UPPERMOST LAYER OF THE OCEANIC
PORTION OF A TECTONIC PLATE.
 Oceanic crust is the
result of erupted mantle
material originating from
below the plate, cooled
by seawater.
 It is primarily
composed
of mafic rocks.
 Generally less than
10 kilometers thick.

3. LIFE CYCLE OF OCEANIC CRUST

4. AT MID-OCEANIC
RIDGE
• OCEANIC CRUST IS
CONTINUOUSLY BEING
CREATED AT MID-OCEAN
RIDGES.
• AS MAGMA RISES INTO
THE UPPER MANTLE AND
CRUST, THE NEW CRUST
FORMED MOVE AWAY
FROM EACH OTHER

5. AT CONVERGENT
BOUNDARY
• THE OCEANIC
LITHOSPHERE THEN SUBDUCT AT
CONVERGENT BOUNDARY.
• THE SUBDUCTION PROCESS
CONSUMES OLDER OCEANIC
LITHOSPHERE.
• THE SUBDUCTED LITHOSPHERE
THAN MELT AND RISE UP
THROUGH CONTINENTAL CRUST
AND FORM ISLAND ARCS.
• BY THE WEATHERING, EROSION,
TRANSPORTATION, DEPOSITION,
AND LITHIFICATION OF THESE
IGNEOUS ROCKS , SEDIMENTARY
ROCKS ARE FORMED.

6. • THAN WITH THE
INCREASE OF
TEMPERATURE AND
PRESSURE OF
SEDIMENTARY ROCKS
DUE TO INCREASES OF
THICKNESS OF
OVERBURDEN,
METAMORPHISM
OCCUR.
• WHEN TEMPERATURE
EXCEEDED THE
UPPER-LIMIT OF
METAMORPHISM
THEN MELTING
OCCUR, & MAGMA IS
FORMED, WHICH
ERUPT AT MID-
OCEANIC RIDGES OR
FROM VALCANOES