Middletown 200 Million Years Ago and Its Enduring Legacy: Part 1
Contributed by Dana Royer
How far back does Middletown’s history go? We are all participating in Middletown’s current chapter, and we can talk to our parents and grandparents to take us back another 60 or 70 years. When most people think about the starting point of Middletown’s history, they think about Native Americans and their contact with Europeans starting in the 1600’s. For geologists like myself, this hardly qualifies as history; or, at least, not “deep” history. Geologists speak rather blithely about millions of years, despite the human mind being poorly equipped to truly understand what this really means. Nevertheless, Earth’s natural history, over millions of years, provides a primary record for how the Earth works. This, in turn, brings into sharper focus our present-day Earth, including predictions for where our planet may be headed in the coming decades. Studying the past is not only useful for understanding the past, but also for contextualizing the present.
Middletown is no exception to this storyline. There are clues all around us, including ones that you can go see and discover now, that help us to understand why Middletown is the way it is. In this two part series, I explore how two time periods in Middletown’s history, roughly 200 million years ago and 20,000 years ago, have left indelible marks on our city. In particular, I focus on how these events help us to understand the specter of present-day climate change, and why our soils are some of the richest in all of New England. Let’s get started!
Pangea: A Super Continent is Born
200 million years ago, all of the continents were joined in a supercontinent called Pangea (see the global map above). Supercontinents are unstable because Earth’s interior is hot, much like a lid on a pot of boiling water. In Pangea’s case, the zone of instability was along what is present-day North America. Like taffy being pulled apart, basins (low spots) started to form in this weak zone. In Connecticut, one of these basins split the state in half. The state map below shows this basin as the “Great Crack”. Geologists call this the Hartford Basin, and it extends north into Massachusetts.
This map shows what the world looked like 200 million years ago. Middletown was in the subtropics, marked here by a red dot. (Map comes from Chris Scotese’s PALEOMAP project)
This state map of Connecticut shows the two major geologic features. The “Collision” zones were affected by several mountain-building episodes associated with the rise of the Appalachian Mountains, roughly 700 to 400 years ago. During the destruction of Pangea about 200 million years ago, this zone was pulled apart, creating a basin (the “Great Crack” that collected sediment (later turned into brownstone) and had active volcanic activity (forming basalt, which compromises traprock ridges today). This map comes from Michael Bell’s wonderful book Face of Connecticut.
This pulling and thinning of Earth’s crust brought magma to the surface. This volcanic activity would have been similar to Hawaii today: relatively gentle and persistent. The rock that formed from this cooling magma, called basalt, contains minerals that are especially rich in calcium and magnesium. And just like rocks today, these rocks 200 million years ago would have been slowly eroding physically and chemically by the action of water and weak acids present in soil. The eroded sediments would have slowly moved downhill, aided by the action of gravity and rivers. Over several million years, as the basin continued to stretch and deepen, the sediment pile became thick enough that temperatures and pressures were high enough to turn it to stone. This sedimentary rock is our beloved brownstone, a product of weathered basalt 200 million years ago.
The Enduring Legacy of Pangea’s Demise: Lesson 1 – Connecticut Landscapes
Connecticut landscapes are largely shaped by their geologic history. Here in central valley (the “great crack”), the landscape is anomalously flat relative to most New England landscapes. This is partly because we are in a basin, but I will return to this topic in my second post. People tend to live in flat places because it is easier to build, transport goods, etc. You can clearly see this human development in satellite images (see satellite image below; the red pin “A” is in Middletown). The eastern edge of the central basin runs along Rt. 17 in south Glastonbury and along Rt. 77 in Durham and northern Guilford. But our basin is not entirely flat. Basalt weathers more slowly than brownstone, causing the basalt to form ridges (“traprock” ridges).
These ridges, owing to their steep slopes and thin soils, are also difficult to develop. As a result, today many are protected parks. Thus, because of geology, central Connecticut has a series of long, skinny parks. These parks are also clearly visible in the satellite image, extending west and north from Middletown as a series of fingers. Beautiful nearby examples include Mt. Higby in Middlefield (normally accessed from Rt. 66), Bluff Head in northern Guilford (normally accessed from Rt. 77), and Hubbard Park in Meriden. From atop these ridges, you have the paradoxical experience of looking down into (and hearing) the hustle and bustle of the lowlands, but being able to hike north and south for miles without a road crossing.
My favorite place to view the basin is from the hilltops east of the reservoirs in the Maromas area of Middletown, along the blue-blazed Mattabesett Trail. Although these hills are just east of the central basin, you have a clear view to the west across the basin to Powder Ridge.
The Enduring Legacy of Pangea’s Demise: Lesson 2 – Connecticut Soils
Connecticut soils in the central basin are some of the richest in all of New England. Indeed, Connecticut was considered the breadbasket during the Revolutionary War. One reason for this is all the calcium and magnesium locked up in the basalt and brownstone. These elements are needed for plant growth, so usually the more you have the better. If you indulge me to geek out a bit, below is a summary of two soils I downloaded from the Natural Resources Conservation Service (what used to be called the US Soil Survey). Notice that the soil from the central valley has more nutrients in it and is less acidic (higher pH). This is mostly due to the differences in bedrock. And, because the soil is more fertile, the plants are more productive, causing the soils to be relatively rich in nitrogen (low carbon-to-nitrogen ratio). The legacy of farming can also be seen in the satellite image above: a major reason why forests in the central valley were originally cut down was to farm.
The Enduring Legacy of Pangea’s Demise: Lesson 3 – Mass Extinctions
Magma contains a lot of gas, including carbon dioxide (CO2) and sulfur dioxide (SO2). This is especially true with the “Hawaii-style” volcanism that was present in Connecticut 200 million years ago. This volcanism was occurring all along the seam that was ripping apart Pangea, from eastern North America to western Europe and northwestern Africa. Massive amounts of CO2, SO2, and other gases were released into the atmosphere, causing an acute climate crisis. Tools for estimating paleo-CO2 indicate a doubling of CO2 over the span of a few thousand years. What were the consequences of this climate disruption? It turns out the consequences were profound—one of the largest mass extinctions in all of Earth history happened at this time, 200 million years ago. Many of the dominant reptiles went extinct, allowing a previously sub-dominant group, the dinosaurs, to become the new kings of the landscape. (And yes, it is fun to contemplate that 134 million years later, [non-avian] dinosaurs suffered the same fate when a meteor six miles in diameter struck the Earth, wreaking havoc. What giveth also taketh away.)
You may be well aware of the rich record of dinosaur footprints in the Middletown area (and more generally in the central valley). These formed when dinosaurs stepped in soft sediment that was later turned into brownstone. All of the brownstone in the Middletown area post-dates the mass extinction, and so records the rise of dinosaur dominance. Dinosaur State Park is the most popular place to view footprints. Another wonderful spot is the Powder Hill Dinosaur Park in Middlefield, off of Powder Hill Road (check out this and this and this; see photo). Here you can view footprints outdoors and contemplate your place in the universe.
Does the climate crisis from 200 million years ago provide any lessons for our current climate crisis? The total amount of CO2 released to the atmosphere was similar to what will happen if we burn the majority of our fossil fuel reserves. One difference, though, is that our current crises is unfolding about 10 times faster than the crisis 200 million years ago (hundreds vs. thousands of years). This is not good news, because releasing CO2 into the atmosphere quickly causes stronger climate disruptions. Gulp…
Further resources for the general public:
Michael Bell. 1982. The Face of Connecticut: People, Geology, and the Land. Bulletin 110 of the State Geological and Natural History Survey of Connecticut. Wonderful book that explores the intertwining of human and natural history in Connecticut; available online for free.
Jelle de Boer. 2009. Stories in Stone: How Geology Influenced Connecticut History and Culture. Wesleyan University Press. Another outstanding book on Connecticut’s human and natural histories.
Peter LeTourneau. 2017. The Traprock Landscapes of New England: Environment, History, and Culture. Wesleyan University Press. Human and natural histories of our basalt ridges. Richly photographed.
James Skehan. 2008. Roadside Geology of Connecticut and Rhode Island. Mountain Press. A solid primer on Connecticut’s geology.
Contributed by Dana Royer
Dana Royer is a Professor of Earth and Environmental Sciences at Wesleyan University. He is interested in the paleoclimate and paleoecology of terrestrial ecosystems that are millions of years old, and has published over 60 papers on these topics. He teaches courses on environmental studies, climate change, paleontology, and soils.