<p>Definitely double major in Geology and Physics. Geology majors are in demand due to the boom cycle and physics majors are always sought out for their quantitative skills. These two majors also go hand and hand.</p>
<p>Ecology has poor job prospects and doesn’t teach you that many useful skills that employers would be attracted to. It basically says you know how to memorize and have very basic lab experience from ecology courses.</p>
<p>A double major isn’t nearly as impressive as students think it is. Do it if you’re going to be taking the courses anyway and want credit for them, but don’t think you’ll miraculously get much better job or grad school prospects just because you double majored. (Something like accounting or finance would be more practical than physics for job prospects anyway. A great many mathematicians and engineers would like to believe that harder majors are automatically held in higher esteem by employers, but unfortunately for them that is often not the case.)</p>
<p>It really does come down to what you want to do. Ecology and physics lead very different places. I appreciate physics and find it interesting, but I would never have chosen it over ecology. My friends in the astrophysics program here would say exactly the opposite. In geology, ecology leads to paleobiology, environmental geology and science, marine science, etc. Physics leads to seismology, volcanology, fluid (air/ocean) dynamics, etc. Some of the better and more comprehensive geology departments offer biology and/or physics tracks within their programs that might be a good alternative to a double major (i.e. geobiology and geophysics).</p>
<p>Compatibility-wise, ecology actually makes more sense. It’s more linked with geology than advanced physics, so instead of taking two majors that have nothing to do with each other (as in the case of geology and physics), ecology and geology will/could/might actually even overlap.</p>
<p>But if you want rigor vis-a-vis marketability, I suggest taking a lot of mechanical engineering classes or even majoring in it. Very useful for geology esp with surface processes, rock rheology, some geophysics, some sedimentology and petrology.</p>