Question

In an ocean basin, a 4 Ma old oceanic crust lies 40 km away from the ridge axis. The average velocity (in cm/yr) of the oceanic lithosphere is ............

Hint:

To calculate the average velocity of the lithosphere, simply divide the distance by the time in the correct units.

Answer 1

Correct Answer: 1

Given information:

• Age of oceanic crust: 4 Ma (million years)
• Distance from ridge axis: 40 km

Concept:

At a mid-ocean ridge, new oceanic crust forms at the ridge axis and moves away symmetrically on both sides. The distance from the ridge axis represents half the total spreading.

Calculation:

The velocity of oceanic lithosphere can be calculated as:

$$v = \frac{\text{Distance from ridge}}{\text{Age of crust}}$$

Converting units:

• Distance: 40 km = 40,000 m = 4,000,000 cm
• Age: 4 Ma = 4 × 10⁶ years

Velocity:

$$v = \frac{4,000,000 \text{ cm}}{4 \times 10^6 \text{ yr}}$$

$$v = \frac{4 \times 10^6}{4 \times 10^6} \text{ cm/yr}$$

$$v = 1 \text{ cm/yr}$$

Answer: 1 cm/yr