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Measurements in mines and boreholes indicate that Earth's interior temperature increases with depth at the average rate of \(30 \mathrm{C}^{\circ} / \mathrm{km}\). Assuming a surface temperature of \(10^{\circ} \mathrm{C}\), at what depth does iron cease to be ferromagnetic? (The Curie temperature of iron varies very little with pressure.)

Short Answer

Expert verified
Approximately 25.33 km.

Step by step solution

01

Understand the Problem

You need to determine the depth at which the temperature of Earth is equal to the Curie temperature of iron, given the surface temperature and the temperature gradient with depth.
02

Identify Given Values

The surface temperature is given as \(10^{\circ}\mathrm{C}\). The temperature gradient is \(30^{\circ}\mathrm{C}/\mathrm{km}\). The Curie temperature of iron is needed, which is approximately \(770^{\circ}\mathrm{C}\).
03

Set Up the Equation

The temperature at a certain depth \(d\) is given by the equation: \(T = 10 + 30d\), where \(T\) is the temperature in degrees Celsius and \(d\) is the depth in kilometers.
04

Solve for Depth

Set \(T\) equal to the Curie temperature of iron: \(770 = 10 + 30d\). Now, solve for \(d\):\[770 = 10 + 30d\]\[770 - 10 = 30d\]\[760 = 30d\]\[d = \frac{760}{30}\]\[d \approx 25.33\]
05

Interpret the Result

The depth at which the Earth's interior temperature reaches the Curie temperature of iron is approximately 25.33 kilometers.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Temperature Gradient
The concept of a temperature gradient refers to the rate at which temperature changes with distance within a given medium. In the context of Earth, the temperature gradient is crucial for understanding how heat is transferred from the planet's interior to its surface. In our exercise, we are told that the temperature increases at an average rate of \(30 \mathrm{C}^{\circ} / \mathrm{km}\). This means that for every kilometer you travel deeper into the Earth, the temperature rises by 30 degrees Celsius.This gradient is significant because it provides insights into geothermal energy and the movement of tectonic plates. High-temperature gradients can lead to volcanic activity and create conditions for geothermal energy extraction. In our calculation, we used this gradient to estimate how deep into the Earth's crust you would need to go before reaching the Curie temperature of iron.
Curie Temperature
The Curie temperature is the specific point at which certain materials lose their permanent magnetic properties. This is particularly important for understanding the behavior of ferromagnetic materials, like iron, under varying temperature conditions.For iron, the Curie temperature is approximately \(770^{\circ}\mathrm{C}\). Beyond this temperature, iron transforms from a ferromagnetic material鈥攚here magnetic domains are aligned to produce a net magnetic field鈥攖o a paramagnetic state, where such alignments cease to exist.Knowing the Curie temperature is crucial in various applications, such as designing motors, transformers, and magnetic storage devices. In mining and geological studies, reaching the Curie temperature within Earth's crust signifies a change in how iron will behave structurally, impacting the geological magnetic records that scientists study.
Earth's Interior Temperature
Exploring the Earth's interior temperature helps us understand the dynamic processes occurring beneath the surface. Temperatures within Earth don't remain constant; they increase significantly with depth, shaped by internal heat sources such as radioactive decay and residual heat from planetary formation.Borehole and mine measurements suggest that starting from a surface temperature of \(10^{\circ}\mathrm{C}\), the warmth of Earth's interior grows as you delve deeper, governed by the established temperature gradient. This warming curve, going from the lithosphere through deeper layers like the mantle, impacts geological phenomena such as mantle convection and plate tectonics.In our exercise, understanding Earth's interior temperature enabled us to calculate the depth at which specific temperature milestones, like the Curie temperature of iron, would be achieved, demonstrating the relationship between depth and heat in Earth's structure.

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Most popular questions from this chapter

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