by things growing annually in a circular fashion
Annual growth rings are commonly studied in trees.
annual rings
The annual rings provide the age of the tree, one annual ring equals one year of growth.
the annual growth rings
Annual growth rings.
annual growth rings
Annual growth rings
I suppose both will show annual growth rings or stages.
In the tropics trees do not stop growing. they grow at a constant speed throughout the seasons because in the tropics it is alsways hot and humid. Tropical trees do not have "annual growth rings" per se, meaning that the rings seens in a cross section are just growth rings (not annual ones). This is in contrast to trees that grow in the temperate zones that have 4 well defined seasons. In these zones the trees do not grow in winter. In the spring, with new growth, the cambium layer of the tree trunk puts out new xylem and phloem cells which form a new "annual ring" over the cells which stopped growing during winter. These are genuine "annual rings" and tropical trees do not have these because they do not experience periods of growth and non-growth.
Tree growth rings (and some other kinds like those of shells) are caused by the difference in growth during the different seasons: autumn and winter less growth, spring & summer more growth.
it depends on how old it is, for every 2 growing seasons, spring and summer, is one growth ring.
More material is added on its outside from year to year (giving rise to annual growth rings).