Explosions (?) near Devils Dyke?

On a walk to the Dyke today, my partner and I occasionally heard a deep booming/popping like noise. At one point, we heard it and turned to see some smoke rising from the direction of the sound. Does anyone know what this might be? A photo of where we saw the smoke is attached.

On a walk to the Dyke today, my partner and I occasionally heard a deep booming/popping like noise. At one point, we heard it and turned to see some smoke rising from the direction of the sound. Does anyone know what this might be? A photo of where we saw the smoke is attached.