In 2018 researchers found that many of the red spruce forests had started to recover from the damage caused by acid deposition. Based on this research, a group of scientists hypothesized that coal-fired power plants were a likely source of the pollutants that lead to acid deposition in the red spruce forests.

The earth's inner core is the earth's innermost part. it is primarily a solid ball with a radius of about 1,220 km (760 miles), which is about 70% of the moon's radius.[1][2] it is composed of an iron–nickel alloy and some light elements. the temperature at the inner core's surface is approximately 5,700 k (5,430 °c), which is about the temperature at the surface of the sun.