# What is the reason behind the density being negative value

This is the example density depth functions for various sedimentary sections world wide. But someof the sections marked with red, due to their last term, as i increase the value of z(depth) they become negative. But density can never be negative? What could be other possible reason for

• What's the source of the table? It could just be a unit problem. For example, if you input the depth in kilometers you'll get more reasonable, positive values until a greater depth. The density seems to be in g/cm3 instead of kg/m3, so you never know... The unit of $z$ is not mentioned in the caption but could be in the main text. Commented Oct 30, 2023 at 6:13
• Those a local, second order fits to data. They cannot be valid globally (i.e. for all z). Search in the text what the limitations on the validity of the fit in z is. Commented Oct 30, 2023 at 15:30
• Mark, you need to get in the habit of giving additional explanation of where these tables you keep asking about are from. This has been a consistent problem with your questions. Context is important to asking worthwhile questions. Otherwise it's only answering the question for you, and without key information often. -1 Commented Oct 31, 2023 at 6:54