Question

The lithostatic pressure at the base of a 35 km thick continental crust of average density of 2.8 g/cc is................ \(\times 10^8\) Pa.

Hint:

Lithostatic pressure can be calculated using the formula \( P = \rho \cdot g \cdot h \), where \( \rho \) is the density, \( g \) is the gravitational acceleration, and \( h \) is the height of the rock column.

Answer 1

Correct Answer: 9.8

Step 1: The pressure rule.
The weight of a rock column gives a pressure \[ P = \rho g h, \] where $\rho$ is density, $g$ is gravity, and $h$ is the column height.

Step 2: Fix the units.
We convert to SI. Density 2.8 g per cc is $2800$ kg per cubic metre, and 35 km is $35\times10^{3}$ m. Take $g = 9.8$ m per second squared.

Step 3: Put the numbers in.
So \[ P = 2800 \times 9.8 \times 35\times10^{3}. \]

Step 4: Multiply it out.
The product comes to \[ P = 9.8 \times 10^{8}\ \text{Pa}. \]

Step 5: State the answer.
The lithostatic pressure at the base is $9.8 \times 10^{8}$ Pa.
\[ \boxed{9.8 \times 10^{8}\ \text{Pa}} \]