Geologists drilled a deep borehole into the Earth's crust at a research site and measured … — ACT

Geologists drilled a deep borehole into the Earth's crust at a research site and measured the rock temperature at various depths. The recorded temperatures are shown in the table below:

Depth ( $m$ )	Temperature ( $^\circ\text{C}$ )
$0$	$12.0$
$250$	$19.5$
$500$	$27.0$
$750$	$34.5$
$1,000$	$42.0$

Assuming the temperature continues to increase linearly with depth at the same rate observed between $0\text{ m}$ and $1,000\text{ m}$ , what will the rock temperature, in degrees Celsius ( $^\circ\text{C}$ ), be at a depth of $1,800\text{ m}$ ?

Answer: 66 °C

Answer

The projected rock temperature at a depth of 1,800 m is 66.0°C.

The correct calculation determines that the temperature increases by 7.5°C for every 250 m (a rate of 0.03°C/m). Extrapolating linearly to 1,800 m, the temperature increases by 54.0°C (0.03°C/m * 1,800 m) from the surface baseline of 12.0°C, yielding a final temperature of 66.0°C.

Step-by-Step Solution

Calculate the rate of temperature change per meter of depth.

0.03^\circ\text{C/m}

Using the interval from

0\text{ m}

250\text{ m}

, the temperature increases by

19.5^\circ\text{C} - 12.0^\circ\text{C} = 7.5^\circ\text{C}

. The rate of change is

\frac{7.5^\circ\text{C}}{250\text{ m}} = 0.03^\circ\text{C/m}

Calculate the total temperature change over the depth interval of 1,800 m.

54.0^\circ\text{C}

Multiplying the constant rate of temperature change (

0.03^\circ\text{C/m}

) by the target depth (

1,800\text{ m}

) yields the total increase in temperature from the surface:

0.03 \times 1,800 = 54.0^\circ\text{C}

Determine the final temperature by adding the increase to the baseline surface temperature.

66.0^\circ\text{C}

Adding the

54.0^\circ\text{C}

increase to the baseline temperature at the surface (

12.0^\circ\text{C}

) gives the projected temperature at depth:

12.0^\circ\text{C} + 54.0^\circ\text{C} = 66.0^\circ\text{C}

Key Concept

Extrapolation of linear data trends

Estimated Time:1m 30s

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