What is a growthring?

Answer 1

A growth ring, or annual ring, is the remnant of a Cambrian Layer.

The Cambrian layer is the surface of a tree trunk, located directly beneath the bark layer.

As the tree grows, it grows from the outside surface of the Cambrian layer, further expanding the bark layer.

Because the tree grows from a small twig whose diameter is very small, those layers are very close together; succeeding Cambrian layers become progressively further apart, until in a tree the size of a Sequoia they can be as far as 3/4" apart.

A cross-section of an adult tree will show a tiny dot at the center called pith. surrounding the pith will be concentric circles, Cambrian layers or growth rings.