On a recent trip to St. Louis, far from my adopted home state of Maine, I was reminded that Missouri was once adjacent to a sea: the Sea of Kansas. The evidence of this can be seen in the limestone cliffs that border Midwestern highways and the fossils that are found in the surrounding rocks. You can also unexpectedly learn about it at the St. Louis Zoo at a new dinosaur exhibit that shows the geologic periods that have changed conditions drastically in this part of the country.

I often joke with my family about moving far away to live by the ocean and being unwilling to ever leave it. To me, the Midwest embodies being landlocked, smack in the middle of the country far from the escape of the vastness of the ocean. But, it struck me particularly on this visit, having flown into this middle place, how one half of the country had once been nearly entirely disconnected from the other.

While the Kansas Sea split the current continental United States down the middle, it actually wrapped around the entire eastern chunk from the bottom around Texas and from the top through Canada, connecting the Maine coast to the Kansas “coast.” So, perhaps there is some very tenuous very ancient explanation for why I was so drawn to Maine having grown up in the Midwest.

The other amazing thing this exhibit reminded me of is that, while we think of dinosaurs as some of the most ancient creatures, many of those in the ocean precede them by literal eons. For example, this ancient sea was filled with an assortment of marine life that is still around today. It was a shallow tropical sea — something that appeals at certain times in the Maine winter — that was filled with things like sponges and corals.

These sponges arrived on the planet some 300 million years before dinosaurs, followed by jellies (the correct name for jellyfish since they aren’t really fish) 265 million years ago, followed by stony corals (as opposed to the soft ones that don’t form reefs) that appeared around 240 million years ago. The Kansas Sea was also home to flying dinosaurs like pteropods and ancient sea birds, one of the reasons you can find oddities like pelicans in Wyoming.

Above all, this exhibit served for me as a humbling experience, particularly on the heels of Earth Day last week. It was a reminder that things are in a constant state of change and that it is important to appreciate the Earth that we have now and how amazingly short our time on it as humans has been. Whether we live on the sea or inland, it is truly all connected – maybe not in the way that it always has been. And, it may not stay connected in the same way in the future. But, for now, those of us who do live along the present-day coast can perhaps have a deeper appreciation for the ancient history of our planet and how we are now entrusted as stewards of its future.