Tree rings

Contorted rocks in a small cave

Bell Island is a rock in the middle of Conception Bay made up of Ordovician age siltstones and sandstones. The sedimentary beds were laid down in a shallow sea between 480 - 444 million years ago.

Sedimentary rocks can tell a story just like tree rings. Tree rings can tell us something about the environmental conditions when the tree was growing. Each year as a tree grows it lays down a new layer which we see in cross-section as tree rings. A hot dry growing season will result in a narrow ring whereas a wet season will result in a wider annual growth ring.

The same can be said about sedimentary rocks except that the composition of sedimentary beds tells us something about the depth of the sea where the beds were laid down. Sediments laid down in a shallow sea will be coarser than those laid down in deeper water. This is because as water deepens it loses its ability to transport sediments and the particles drop out. Therefore, sandstones are laid down in shallower water than siltstones because siltstone particles are finer.

Each layer of rocks in the cliff faces of Bell Island tells us that environmental conditions changed, not on an annual basis but over a period of millions of years. Knowing something about the geology of an area adds to the interest of my paddles.