The geothermal gradient in non-volcanic areas is typically around 25-30°C per kilometer of depth. This means that for every kilometer you go deeper into the Earth's crust, the temperature increases by 25-30 degrees Celsius.

However, this is just an average. The actual gradient can vary significantly depending on:

* Location: The geothermal gradient can be higher in areas with a lot of tectonic activity, like near plate boundaries.

* Rock type: Rocks with higher thermal conductivity will allow heat to transfer more easily, leading to a steeper gradient.

* Water content: Water can act as a heat transfer agent, leading to a higher gradient in areas with more water.

Here are some examples of how the geothermal gradient can vary:

* Continental crust: Typically 25-30°C/km.

* Oceanic crust: Can be higher, up to 50°C/km.

* Areas with high heat flow: Geothermal gradients can reach 100°C/km or more.

It's important to note that the geothermal gradient is not a constant value. It can fluctuate over time and space due to various geological processes.