Why does the thunder from lighting last much longer than the flash?

[cantgetaname]

I was walking home today when I noticed that the flash from a lighting takes a fraction of a second while the sound lasts a good 5-6 seconds.
I couldn't think of an explanation for this, except a wild guess that maybe the source of sound is a line source and sound from different points on the lightning bolt takes different times to reach the observer.

 

[olivermsun]

That's most of the answer. Lightning bolts can be miles long. Sound in air needs several seconds to travel a miles-longer path. Another answer depending on your surroundings is the presence of echoes, which create additional paths.

 

[rcgldr]

Here is a video of an unusual (for southern California) thunderstorm. There are a few instances where you see the flash and hear the thunder. At this particular location, echoes from nearby hills add to the sound.

https://www.youtube.com/watch?v=46yPXf2DwXc