Question

Oceanic crustal rocks are much younger than continental crust rocks. Explain with the help of the concept of seafloor spreading.

Answer 1

Approach:

• try to establish that Oceanic crustal rocks are much younger than continental crust rocks.
• Then give the theoretical understanding of seafloor spreading for an explanation.

Answer:
The age of rocks in the oceanic crust is not more than 200 million years, whereas some of the continental rock formations are as old as 3200 million years.

• The reason for ocean crust is much younger than the continental crust is best explained by seafloor spreading theory:
• the ocean floor moves laterally under the influence of convectional magma currents.
• Rising limbs of these currents cause divergence of the lithospheric plates, creating new crust.
• Failing limbs cause lithospheric plates to converge, creating trenches near the subduction zone. At the subduction zone, the oceanic plate is melted at a depth due to heat, completing the ocean floor formation and destruction cycle.
• The evidence of spreading boundaries can be concluded from the fact that along the ridge, there is the formation of paired rocks that are similar in age and composition.