As a general rule at Oxford University for all subjects they like to interview 3 applicants for every place. Earth sciences doesn't get that many applications and therefore they end up interviewing almost everyone. Reasons vary why people don't get called for interview but the two commonest are: a) people confuse earth sciences with environmental sciences and write about env sci in their personal stmt, b) people apply without the predicted or actual minimum entry requirement in the vain hope of being selected. lol