Pennsylvania's 50-Year-Old Coal Fire

What was the most likely cause of the Centralia coal fire?

• A lightning strike during a thunderstorm.

• A brush fire spreading into a mine.

• Sanitation workers burning trash too close to a mine entrance.

• Spontaneous combustion of low-grade coal.

What does it mean for a reaction to be spontaneous in thermodynamics?

• It happens very quickly and suddenly.

• It requires a large amount of energy from an outside source.

• It occurs without needing energy input from an outside source.

• It only happens at extremely high temperatures.

What is one dangerous consequence of underground coal fires burning for a long time?

• They cause the ground above to collapse, creating sinkholes.

• They make the surrounding air colder.

• They increase the amount of moisture in the soil.

• They make the coal stronger and more stable.

Why did pouring cement into the Centralia mine fire not help extinguish it?

• The cement reacted with the coal to create more fuel.

• The high temperatures burned away the cement, creating more gaps for oxygen.

• The cement was too heavy and caused further ground collapse.

• The fire was too deep for the cement to reach.