Hope:
I am disappointed to receive no response from you to a rather long post containing lots of scientific information. Disappointed but not surprised, as my long experience is that quite often when I start providing evidence, creationists disappear.
Nevertheless I wanted to return to you to explain what I found disturbing about your earlier post, depending on what you meant by an assumption of uniformitarianism, as that term is ambiguous. If all that you meant is that geology rules out in advance the possibility of any cataclysmic events, that is not true. Not only does modern geology allow for cataclysms of all kinds, in fact, it posits them. There is no presumption that everything that we see can only have resulted from slow, gradual processes, only a conclusions that many/most of them did.
On the other hand, if you are asking why scientists in general assume that nature tends to have laws which remain constant, and further assume that we can base our knowledge of the past on observations in the present, assuming constant and uniform natural laws, then you are questioning one of the most fundamental tenets of science, without which science itself is not possible. This willingness to basically make science impossible, in order to promote a creationists agenda, is just one of the reasons scientifically minded people find creationism threatening--it is.