Geology
Like some of the other mentioned options it lets you work outdoors, and often in remote locations based out of bush camps, but has several other distinct advantages.
Geology is a broad field that prepares you for all sorts of careers. You could work in the private sector for companies such as mineral exploration, mining, oil/gas, water/hydro. You could work for the government: geological surveys. It is a valubale background for other career paths such as investing, civil construction etc.
Geologist have the oportunity to travel all over the globe, work from home, office, or out in the bush, or a combination of all of the above. You can be employed, or work as a private consultant which is popular these days.
Geologists are very well payed (another great bonus), and if working for industry have the option to rise into managment quickly. Right now with China industrializing, and metal and oil prices on the rise, there are more jobs than geologists - basically letting us write our own tickets. (Did I mention, I am a geologist

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Most people in geology programs are into the outdoors, and it is a really fun undergrad program. Lots of field trips, and several classes are completely field based where you are out in the bbush for several weeks at a time, often in tent camps. Also, being a broad area of study, it lets you experience lots of the science without forcing you to specialize early on like most other sciences, and especially engineering do. That is great if you are not sure exactly what you like right off.
Will