Mechanisms for Inhmogeneity in Earth's Crust

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In summary, the second law of thermodynamics applies to the mixing of cream in coffee and the formation of mineral deposits on Earth. The Earth's complex processes such as differentiation, plate tectonics, and the water cycle have led to the diverse mineral deposits found on our planet. The timing of unmixing and the formation of mineral deposits is still being studied and there are many resources available to further explore this topic.
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anorlunda
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Mix cream in coffee and it never unmixes. Even though the cup of coffee is not a closed system, the second law of thermodynamics seems to apply anyhow.

The Earth was once a molten ball. I presume that it was well mixed. It is not a closed system either.
But today's Earth seems very unlike the creamed coffee; especially in the crust.

I am wondering how we can find so many rich mineral deposits all over. Both light and heavy minerals. We find veins of gold and other metals. We find ores with concentrated amounts of aluminum, or lithium or hundreds of other minerals. We even find pockets of helium. A visit to the Grand Canyon made me appreciate the incredible diversity of rock.

I understand stratification by density. But mineral finds are both light and dense. I understand that chemical reactions can cause precipitates to fall out of a liquid such as sea water, but I have a hard time visualizing that in viscous magma. Distillation? Yet even distillation sounds wrong because there are so many diverse minerals found concentrated in so few places. I would expect that a single mechanism acting world wide would produce homogeneous results, not diversity.

I am also interested in the timing of unmixing. Whether it happened before or after the crust solidified. Could the planetesimals that formed the Earth have been enriched before becoming part of the Earth such that their mass never did get thoroughly mixed?

I can't find anything useful on Wikipedia. Wikipedia is great, but only if you can guess the right terms to search for.

Can anyone help point me to articles or publicly available sources where I could study this subject more?
 
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Interesting question! The second law of thermodynamics states that in any natural process, the total entropy (or disorder) of the system and its surroundings will always increase. This means that in the case of mixing cream in coffee, the cream will never unmix itself because the process of mixing increases the entropy of the system.

In the case of the Earth, the second law of thermodynamics still applies, but it is a much more complex system. The Earth has undergone many processes such as differentiation, crystallization, and plate tectonics that have led to the formation of diverse minerals and mineral deposits.

One important factor in the formation of mineral deposits is the Earth's internal heat. As the Earth cooled and solidified, different minerals began to crystallize at different temperatures, leading to the formation of different layers within the Earth's crust. This process is known as differentiation.

Plate tectonics also plays a crucial role in the formation of mineral deposits. As the Earth's plates move and interact with each other, they can cause the formation of different types of rocks and minerals. For example, when two plates collide, they can create mountain ranges which can contain rich mineral deposits.

Another important factor is the Earth's water cycle. Water plays a crucial role in the formation of many types of mineral deposits through processes such as weathering, erosion, and sedimentation. For example, gold can be deposited in streams and rivers through the process of sedimentation.

The timing of unmixing and the formation of mineral deposits is a complex topic and is still not fully understood. It is believed that some mineral deposits were formed during the early stages of the Earth's formation, while others may have formed later on through processes such as metamorphism.

As for finding articles or sources to study this subject more, I would recommend looking into geology textbooks or articles published in scientific journals such as Nature or Science. You can also try searching for keywords such as "mineral formation," "plate tectonics," or "Earth's water cycle" to find more specific information. Good luck with your research!
 

1. What causes the differences in composition and structure within Earth's crust?

The primary mechanisms for heterogeneity in Earth's crust are plate tectonics and volcanic activity. Plate tectonics involves the movement and collision of large landmasses, which can create variations in crustal composition and structure. Volcanic activity can also introduce new materials into the crust, further contributing to its heterogeneity.

2. How do scientists study the heterogeneity of Earth's crust?

Scientists use a variety of methods to study the heterogeneity of Earth's crust, including seismic imaging, geochemical analysis of rocks and minerals, and geologic mapping. These techniques allow researchers to identify and map variations in crustal composition and structure.

3. What role does the ocean play in creating heterogeneity in Earth's crust?

The ocean plays a crucial role in the creation of heterogeneity in Earth's crust. The movement of oceanic plates and the formation of oceanic crust through seafloor spreading contribute to the diversity of crustal composition and structure. The presence of water also influences the physical and chemical processes that occur within the crust.

4. How does the age of Earth's crust contribute to its heterogeneity?

The age of Earth's crust is a significant factor in its heterogeneity. Older crust tends to be thicker and more stable, while younger crust is thinner and more prone to deformation and volcanic activity. This leads to variations in crustal thickness and composition, contributing to its overall heterogeneity.

5. Can the mechanisms for heterogeneity in Earth's crust change over time?

Yes, the mechanisms for heterogeneity in Earth's crust can change over time. Plate tectonics, for example, is a dynamic process that has evolved over Earth's history, resulting in changes to the composition and structure of the crust. Volcanic activity can also vary in intensity and location, leading to fluctuations in crustal heterogeneity.

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