Chapter 4: Problem 4

Why do the gases in magma not form gas bubbles when the magma is deep within the crust?

Short Answer

Expert verified

The gases in magma do not form gas bubbles when the magma is deep within the crust because the high pressure exerted on the magma at those depths keeps the gases dissolved in the magma and prevents them from forming gas bubbles. As the magma ascends and the pressure decreases, the gases become less soluble, allowing gas bubbles to form.

Step by step solution

Understanding Magma and Gases

Magma is a molten or partially molten mixture of minerals, gases, and sometimes crystals, which is found deep within the Earth's crust. The gases within magma are primarily composed of water vapor, carbon dioxide, and sulfur dioxide. These gases remain dissolved in the magma under high pressure conditions deep inside the Earth.

Formation of Gas Bubbles

The formation of gas bubbles within magma largely depends on two factors: the solubility of the gases and the pressure exerted on the magma. The solubility of gases in magma decreases with decreasing pressure, while the pressure exerted on the magma generally decreases as it ascends towards the Earth's surface.

Pressure and Solubility Relationship

When the magma is deep within the Earth's crust, the pressure exerted on it is extremely high due to the weight of overlying rock. This high pressure keeps the gases dissolved in the magma and prevents them from forming gas bubbles. The relationship between pressure and solubility can be described using Henry's Law, which states that the solubility of a gas in a liquid is directly proportional to the partial pressure of the gas above the liquid.

Effect of Depth on Gas Bubble Formation

As the magma rises through the Earth's crust towards the surface, the pressure on the magma decreases. The decrease in pressure causes the solubility of the gases within the magma to decrease as well. As a result, gas bubbles have the potential to form within the magma as it ascends. To summarize, the reason why gases in magma do not form gas bubbles when the magma is deep within the crust is due to the high pressure exerted on the magma at those depths. The high pressure keeps the gases dissolved in the magma and prevents them from forming gas bubbles. However, as the magma ascends and the pressure decreases, the gases become less soluble, allowing gas bubbles to form.

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Why do the gases in magma not form gas bubbles when the magma is deep within the crust?

Short Answer

Step by step solution

Understanding Magma and Gases

Formation of Gas Bubbles

Pressure and Solubility Relationship

Effect of Depth on Gas Bubble Formation

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