Temperature and density increases from the crust to the core.
The correct answer is - ozone.
The ozone is essentially three molecules of oxygen, or O³. This gas is crucial for the life on the Earth because it is the one that manages to filter out big portion of the UV radiation from the Sun which is extremely harmful if its too strong, as it will contribute to the dying out of pretty much every living organism.
While the ozone layer in the stratosphere is very useful, the ozone in the lower parts of the troposphere is actually considered as pollutant. The reason why it is considered as pollutant is because it is very harmful if inhaled, and it also heavily damages the plants.
25% of the civilians were killed in September 2015
The polar ice capes, the change in genetics of certain animal fossils (growing more or less hair, etc. etc.)
In 60 years, from 1801 to 1862, the amount of cotton picked daily by an enslaved person increased 400 percent. The profits from cotton propelled the US into a position as one of the leading economies in the world, and made the South its most prosperous region.
