Altitude

So, we had a wonderful time in CA. Jason spent a TON of time with my dad. They went golfing and worked on the Christmas lights and went on errands and dad even started teaching Jason how to drive the motorcycle (without my knowledge, but he did come back in one piece).
We had a great Thanksgiving with tons of food, which was great because I was always hungry. I ate two complete dinners and desserts, one with each set of Grandparents. I think it was wonderful that as soon as we got to CA my morning sickness was gone. There were times that my stomach started to hurt and I needed to eat again, but I was not sick all the time. I was hoping that it would stay that way, but no such luck. I am sick again. Ugh. Why does altitude play such a big role in whether or not you suffer morning sickness? 100ft vs 45oo ft above sea level.