Primary Science: Taking the Plunge is a classic in our field (I teach K-4 science). I inherited my copy from a retired elementary school science teacher and found it inspirational in shaping my thinking.
You may find it hard to find a job teaching just earth science to elementary - all the elementary science jobs I've seen were positions that included teaching a variety of scientific topics - but if you are a scientifically-minded, curious and motivated person that shouldn't be a barrier to you being successful. For example, I started my current position knowing almost nothing about rocks (my background is in biology), but since it was on my curriculum for second grade, I started reading - and I now really enjoy teaching rocks.
Elementary school science teacher is about the most fun job I can imagine having. Good luck!
If you are working with younger students, I recommend Primary Science: Taking the Plunge by Wynne Harlen (a fellow Brit, too).