Couple thoughts
#1 Trust me, college is better then high school. It's hard to look at any transition like this objectively because you have memories and friends that have a sentimental value to you that you are trying to compare to experiences you have yet to have. Living in the dorms you'll make friends fast and the amount of time you spend around those people will increase the friendships. Freshmen year may indeed be the best year of college for a lot of people, I would probably rate it as my favorite year honestly. The age thing I wouldn't worry about, that type of shit is meaningless when you are all adults. It's just 1 more year of being 21+ on campus. And anyway guess what when the year is over you'll come home for the summer and most of your hs friends will still be around.
#2 In terms of being depressed about majoring in geography, there is nothing stopping you from changing majors if you want to. You probably aren't jumping right into major classes are you? Take some GEC's and give yourself time to poke around at the different majors (god knows there are plenty of them). You have plenty of time to explore all your options major wise without setting yourself behind in terms of graduating.