If you managed to get past the Crab boss in Area 5 of Blaster Master, you get to move on to the ice stage, Area 6, which features these blocks that you have to destroy from below to proceed.

But, say you need to check your status screen for some reason, or you just want to pause the game for a breather

Once you leave the status screen...

The blocks are back!

I sure hope you didn't need to go back down that shaft.

Also, as a bonus tip: the boss's room is to the right once you get to the top of this shaft. If you go left it'll lead you back to beginning of the stage, and some of these mysterious blocks will be back, making you take the long way around.