sentence structure !!
Q: Surplus snowfall is essential for a glacier to develop.A surplus allows snow to accumulate and for the pressure of snow accumulated over the years to transform buried snow into glacial ice with a depth great enough for the ice to flow.

I understand the meaning of the sentences above. i want to know the sentence structure of the second sentence.
"and for the pressure of snow accumulated over the years to transform buried snow into glacial ice" which is the subject and which is the verb? can anybody tell me the original way to put it ?

Question

sentence structure !!
Q: Surplus snowfall is essential for a glacier to develop.A surplus allows snow to accumulate and for the pressure of snow accumulated over the years to transform buried snow into glacial ice with a depth great enough for the ice to flow.

I understand the meaning of the sentences above. i want to know the sentence structure of the second sentence. 
"and for the pressure of snow accumulated over the years to transform buried snow into glacial ice" which is the subject and which is the verb? can anybody tell me the original way to put it ?

Answer

As far as I can tell the verb is still "allows" so if you take out the "snow to accumulate and" you have "A surplus allows for the pressure of snow accumulated over the years to transform buried snow into glacial ice with a depth great enough for the ice to flow."

I am not sure why it would use just "allows" and then add a "for" instead of using "allows" or "allows for" for both and I agree that it was confusing - I myself had to take a moment to sort out what they were trying to say. At the same time, this could very easily be the wrong answer - it's just a poorly worded sentence.

Answer

It is easier if you break down the sentence into more manageable pieces:

"A surplus allows snow to accumulate and to transform buried snow into glacial ice by means of its increasing pressure. The glacial ice will have a depth great enough to allow the ice to flow."