It was hard for me to get a really good photo to demonstrate what I am trying to share.
Do you see how the bag is all puffed up full of air? Pretty cool, huh?
We get this a lot where we live.
We live at high altitude (around 5,500 feet).
We see a lot of potato chip bags on the store shelves like this, too.
The same thing happens to sealed bags of goodies when we drive over high mountain passes. Also, if you start to drink water from a plastic bottle at a lower altitude, put the lid back on, and then drive up higher and higher into the mountains, the bottle compresses or crumples inward, often making a really loud, abrupt crackling noise that tends to startle the heck out of us when we are driving along. "Holy cow! What was that?!"
I never noticed this phenomenon when we first moved here to high altitude Southern Colorado, but my doctor actually pointed this out to me when I was late in my pregnancy and I was asking about travel in the 3rd trimester. The doctor said, "you know what happens to potato chip bags when you go over high mountain passes? Well, the same thing can happen to your uterus... expanding and contracting... and it can cause a woman to go into labor early?" Okay, I am paraphrasing.... that conversation happened... oh, over 16 years ago. But whatever the case may be, I find this science stuff pretty cool.
It all has to do with changes in atmospheric pressure which can be explained by clicking HERE.
I also found these explanations Yahoo; looks like folks are able to type in their best explanation of why potato chip bags puff up at higher altitude... some do a better job than others explaining this.
I know this has nothing to do with cooking or baking but I thought this was fun to share in case you've never seen this before. Science is cool!