why does rain after a dry spell create big bubbles on the ground?

Rainfall today, so the grass may start to look less yellow.

After a dry spell, it was a classic day to spot the big surface bubbles that form after a period without much rainfall.

I looked on some nearby asphalt, which, whilst flat, contains plenty of air. When the rain falls the water wants to displace the air, but accumulated oil from cars, soaps and other sources affect the rainwater's surface tension.

So as the water tries to displace the air, it reaches the oily surface water creating the big bubbles.

Ok, for now I smell the rain and it's heading my way.

Ramble On.

Time to enjoy the bass riff and the Les Paul gear changes.