Question

Consider the present volume of the Earth’s continental crust as \(7.5 \times 10^{18}\) m³. If continental crust formation started 3.0 Ga ago, then the average rate of continental crustal growth is ............. km³ yr⁻¹. (Round off to one decimal place)

Hint:

To find the average rate of growth, divide the volume by the time elapsed, and convert the units accordingly.

Answer 1

Step 1: Convert the volume to km³.
The given volume is in m³, and we need to convert it to km³.
Since \(1 \, \text{km}^3 = 10^9 \, \text{m}^3\), we have: \[ 7.5 \times 10^{18} \, \text{m}^3 = \frac{7.5 \times 10^{18}}{10^9} = 7.5 \times 10^9 \, \text{km}^3 \] Step 2: Calculate the average growth rate.
The continental crust has been forming for 3.0 billion years (3.0 Ga). To find the average growth rate, divide the volume by the number of years: \[ \text{Rate of growth} = \frac{7.5 \times 10^9 \, \text{km}^3}{3.0 \times 10^9 \, \text{years}} = 2.5 \, \text{km}^3 \, \text{yr}^{-1} \] Final Answer: \[ \boxed{2.5} \]