You should be able to write 1000 words in 40 min.
Dont prepare more than 1200, because unless you're a crazy writting machine you'll run out of time to finish well and a strong conclusion is vital.
Another way of looking at it is to write 20 x 50. (20 paragraphs of 50 words)
microbes feed off iron from the wreck forming icicle-shaped "rusticles" (35% iron, 65% bacteria, archaea and eucarya)
During this 'feeding' process reduce sulfates...