Is the back hearth made up of compacted earth that can withstand heat from fire?

The statement about the back hearth being composed of compacted earth that can withstand heat from fire is not accurate. Generally, a hearth is built using materials specifically designed to handle high temperatures, such as brick, stone, or concrete. These materials are selected for their ability to insulate against heat and prevent degradation over time.

Compacted earth is not typically used in modern construction for areas exposed to significant heat, as it can degrade and become structurally unsound when subjected to high temperatures from a fire. Modern hearth designs prioritize durability and safety with materials that provide better thermal resistance.

In older designs, there may have been instances where earth was used, but this is not the standard in contemporary construction practices. Therefore, it's important to recognize that while some historical hearths might have included compacted earth, it does not hold true for current building standards.