You need to develop a scientific writing style for essays in physical geography. You would do well to use the most influential scientific journals (Nature and Science, for example) as a guide. These journals are intended for a wide audience; consequently they are written in a concise, accessible style. Avoid the temptation to use complex jargon (perhaps because you think it lends your essay a more ‘scientific’ quality). The use of technical language in scientific writing is unavoidable; however, you should still strive for clarity of thought and expression in everything you write. Use your own words: this lends your writing a consistent voice and helps to demonstrate your understanding of the material. Your tone needs to be measured (exclamation marks rarely appear in scientific literature) and considered. Most importantly, you need to be concise: the law of diminishing returns applies for every word you write above the stipulated limit. If you find yourself writing 2000+ words, you have probably missed the point of the essay. Remember, you will mainly be assessed by examination, so you need to become proficient in writing concisely.
When you write your essay, you should choose an appropriate ‘voice’ (and then stick by your choice). Essays are usually written in the third person:
This essay will explore changes in the cryosphere at various scales, and the extent to which this is linked to sea-level changes.
It is perfectly acceptable to write in the first person, particularly when you are expressing an opinion, or making a statement of intent:
In this essay, I will consider how the different components of the cryosphere impact on sea level and their patterns of change over the last century.
It is best to avoid the ‘Royal we’:
The first part of this essay will provide a brief overview of the cryosphere’s composition and its dynamics. We will then examine the planet’s main ice-sheets, Antarctica and Greenland, and assess their impact on sea level rise. This will then be compared to the contribution of glaciers and ice caps, as well as the effects of sea ice dynamics. We will conclude by reviewing the different impacts of changes in the cryosphere, and expand on other processes that also influence global sea level in the medium-term.
This is OK for research papers with multiple authors, but is sounds awkward in an undergraduate essay.
The Essay writing in Human Geography resource offers some useful advice on the impact of 'over-sophistication' on your writing and adopting a suitably academic 'tone'.