Trees contain some of nature's most accurate evidence of the past. Their growth layers, appearing as rings in the cross section of the tree trunk, record evidence of floods, droughts, insect attacks, lightning strikes, and even earthquakes. Every year that a tree grows its trunk gets fatter. This is because trees don't just grow up they grow out in the form of rings too. The newest growth of a tree is between the bark and the wood that grew the year before.