Question: Is there a formal logic symbol for "why"? For example how would you formulate "Why is 2^4 > 4^2?" Could that be formulated in pure symbols of logic if possible?

Also, the phrase "what is" can it be described with logic symbols? Is it just "=" equals? So for example you walk down the street and hear a bang. And you conclude it's either a car crash or a kid popping a balloon. How would that be expressed logically with symbols?

Answer: 
No. Formal logics deal with concrete propositions, not speculative discussions. Speculations have huge levels of nuances and are usually performed with narrative language. In fact, papers or scientific documents use mostly narrative argumentation, except for the concrete formal propositions, which are written using formal logics.
This sort of thing may have some bearing on answering your question (and won't fit in a comment):

[![enter image description here](https://i.stack.imgur.com/FZjOQ.png)](https://i.stack.imgur.com/FZjOQ.png)
The Oxford Handbook of Epistemology p409

An '[explanandum](https://en.wikipedia.org/wiki/Explanandum_and_explanans)' is what is to be explained