I am not sure but I think the shock part refers to what the person standing near by feels when it happens to them.
Thermal Downshock is what happens when something Hot meets something Cold and it cracks or explodes. As an example: cold water, say from a medicine syringe, hitting a hot light bulb would cause the light bulb to crack. Perhaps crack right along the base and fall from the ceiling shattering into a hundred pieces in the sink. It might look like this:
Not that it was intentional, but it was a great learning experience. I am sure the complete shock of the situation will forever ingrain Thermal Downshock into my children's vocabularies.
*No children were hurt in the making of this blog