If a switch has Spanning Tree Protocol enabled, and I have an unmanaged 8-port switch connected to it, will the STP still detect the loop and disable the port if the loop is in the 8-port switch?
Spanning Tree Protocol
You are correct! The switch that is doing STP will recognize a loop and prevent it.
***Enhanced Answer posted after original reply***
When you connect both of the switches together, the non-managed switch will just forward the BPDUs it has received from the STP enabled switch to the other ports. If another port from the unmanaged switch is connected back to the STP enabled switch in a loop, The original BPDU will look as if it's coming from the unmanged switch and stop prevent the loop.