Ancient reef creatures in Vermont

There’s something special about seeing fossils out in their natural setting. Sure, museums show the best specimens and put them in nice light and make sure the room is not too hot, not too cold. But there’s a certain feeling, something like awe and thrill of discovery mixed together, when you find fossilized life forms in natural settings. To me, it is a nice reminder that we are players in a fascinating earth story that continues to play out all around us. Although Vermont is not often associated with fossils and indeed much of New England is devoid of fossils, Vermont’s Lake Champlain islands contain some fantastic fossilized sea creatures and plants from the Ordovician period that are easily seen in a few spots. One of the best is the Goodsell Ridge Preserve in Isle La Motte, Vermont. The site is the oldest fossilized reef in the world that had some diversity of life (there are older reefs made up of just one species).

We took a day trip from the Burlington area with our two kids to have a look around the site, and it did not disappoint. There are short and easy trails, but the areas of main interest for fossils are right near the entrance. Mounded rocks protruding from the land surface are actually the remains of one of the earliest diverse reefs in the world. You can walk on them, searching for things like gastropods and cephalopods that in some places are easily seen. Below are examples of a gastropod (a snail-type spiral shell), a bivalve (like a clam) and some cephalopods (which are similar to the nautilus but with straight shells).

The Ordovician period started about 485 million years ago, and lasted about 42 million years. The fossils at the reef site in Isle La Motte are about 480 million years old. To put that into context, another 240 million years would elapse before the first appearance of dinosaurs. Moreover, the extinction of dinosaurs was “only” 65 million years ago, which is a long time to be sure, but a small duration relative to the age of the fossils that are visible in Isle La Motte. The early Ordovician was a time when there still were no life forms on land, and the atmosphere had a low oxygen content, only 68% of the modern level. One primary Ordovician life form that is visible at this site is the cephalopod ancestor of modern squids and nautilus. These fossils clearly show their long, pointy segmented shells.  Also abundant are gastropods (spiral snail-like shells), as well as the stromatoporoids and bryozoans that were the primary reef-builders (corals had not yet evolved).

It’s certainly weird that one of the oldest reefs on earth is in Lake Champlain, almost 200 miles from the present Atlantic coast, but this reef originated in the tropics and moved up here to temperature Vermont though tectonic plate movement. So much time has passed that many examples of such reefs have been consumed by geologic processes, making the reef in Isle La Motte a very special place.

To get there, enter 69 Pine St, Isle La Motte, VT, into your GPS or Google Maps. It will guide you right to the entrance. In general, you follow highway 2 northwest from Burlington and then bear west in South Alburg to cross the causeway to Isle La Motte. Once there, allow for plenty of time to explore the outcropping reefs. Our kids loved seeking out fossils on these formations. We also took a short hike, the white trail, which goes around the site and passes through a very nice cedar forest as well. It is easy and well worth doing. We also saw some glacial erratics (large boulders dumped by retreating glaciers after the last ice age), and there are some interesting fossils to be found at the far end of the white trail, including bivalves and bryozoans.