Final answer:
The amount of gases in magma is directly related to the explosiveness of volcanic eruptions. More gases lead to higher pressure, and upon decompression, the gas expansion can result in violent eruptions. Less gaseous magmas tend to produce effusive, less explosive eruptions.
Step-by-step explanation:
The relationship between the amount of gases in magma and the explosiveness of a volcanic eruption is significant. A higher concentration of gases, such as water vapor, carbon dioxide, and sulfur dioxide, can lead to more explosive eruptions. This is because these gases are under high pressure within the magma. As magma rises to the surface, the pressure decreases, allowing the gases to expand.
According to Gay-Lussac's Law, if the temperature remains constant, the volume of a gas is directly proportional to the pressure. Therefore, a sudden drop in pressure can cause the gases to expand rapidly, increasing the volume of the magma and leading to a violent ejection of magma, gas, and ash. This is similar to how releasing the pressure of a carbonated beverage can cause it to fizz and overflow.