Natural science personal statement focused on one subject?

Hey, so I'm thinking of applying for earth sciences at Oxford, and then natural sciences for my other 4 choices (probably Durham, Birmingham, Nottingham, and UCL), mainly because the earth science courses at other unis were less maths/physics and more geography/geology. Anyway my personal statement will primarily be talking about my interests and the books I've read in earth sciences, but will this still make a good personal statement for natural sciences too, or will I be disadvantaged for focusing only on one specific subject within natural sciences?