You might do so for several reasons:
for better opportunity
Because you want a job with more pay?
Beacuse i am not satisfied from total earning
For growth and share the current experience to new organisation
my current job is teaching geology and i have applied to do seimic survey
resigned
Some people might want to leave their job because they don't like it and want to pursue something they enjoy more.
you can say that the job just did not fit what you wanted to do with the of your life
to look for more gainful opporotunities
the job was not what I expected The job was not as presented at time of interview I thought I would enjoy this work however I was mistaken.
Any other information which will support your application?
what other jobs you've done. how other jobs have influenced you. what you know about the union. why you would leave your current job.