Conn Doc G292v West Rocl( to the Barndoor Hills no. 4 cop. 3 The Traprock Ridges of Cotmecticut ... \ j " Cara Lee ( APR ~f ~/jgg0 State Geological and Natural History Survey of Connecticut Department of Environmental Protection 1985 Vegetation of Connecticut Natural Areas .No.4 I j - - - -- STATE GEOLOGICAL AND NATURAL HISTORY SURVEY OF CONNECTICUT DEPARTMENT OF ENVIRONMENTAL PROTECTION West Rocl( to the Barndoor Hills THE TRAPROCK RIDGES OF CONNECTICUT TEXT AND ILLUSTRATIONS Cara Lee Co..,., )oc 6o1Y'o.:...., /1(), y 1985 ( Oj'J. ) VEGETATION OF CONNECTICUT NATURAL AREAS NO. 4 STATE GEOLOGICAL AND ATURAL HISTORY SURVEY OF CON ECTICUT DEPARTMENT OF ENVIRONMENTAL PROTECTION Honorable William O'Neill, Governor Stanley J. Pac, Commissioner of Environmental Protection Hugo Thomas, Director, Natural Resources Center in cooperation with School of Forestry and Environmental Studies Yale University support provided by the Sperry Fund and The ature Conservancy - Connecticut Chapter Acknowledgements Many people helped me to look at traprock ridges the way they do. Their capacities range from engineering to her­ petology to geology and their generously shared enthusi­ asm, talents and skills made this project a pleasure to pursue. Thanks in particular to Ned Childs and his trusty airplane, Lauren Brown, Sue Cooley, Mike Klemens, Ken Metzler, Les Mehrhoff, Barbara arendra, Sid Quar­ rier and Steve Stanne. Diane Mayerfeld was a gracious and thoughtful editor whose help was greatly appreci­ ated. Special thanks to Tom Siccama for never failing to show interest in every aspect of the project as it evolved. This publication is one of a series describing the ecology of natural areas in Connecticut. The previous publica­ tions in this series discussed the vegetation of specific sites that were legally protected as natural areas. This report takes a broader approach. Rather than focusing in great detail on a single area, this book describes the natural history of a habitat type-traprock ridges­ which includes some protected and some unprotected areas in the state. Critical habitats such as traprock ridges are important parts of Connecticut~ natural heritage. In their natural condition, these areas are valuable for education, research, and relaxation, and as refuges for rare species and unusual biological communities. For information on how to order this report or other publications of the Connecticut and Natural History Survey, contact the Natural Resources Center in the Department of Environmental Protection. Contents I Geology 9 The Setting 9 The Sequence 12 II Ecology 20 Traprock as Critical Habitat 20 Growing on a Ridge 22 Wildlife Corridors 28 A Wilder State 33 The Green Belts 36 III Land Use 38 Quarrying the Traprock 38 Hiking, Climbing, and Sometimes Flying 43 People in High Places 48 IV Managing for Diversity 52 Appendices 57 For Further Reading 57 Other Resources 59 Topographic Maps as a Resource 60 8 I 5 LA 9 I. GEOLOGY The Setting In June ofl889, six students from the Harvard University the softer, more gently rounded hills of the surrounding Geology Department arrived in Meriden, Connecticut to valley. spend the summer. Geologists-in-training, they would The prominence of the ridges as a landscape feature in venture into the field every day with Professor William the Central Valley drew the attention of others besides M. Davis, their backpacks bulging with rock hammers, geologists in the late 18008. By the turn of the century, notebooks, compasses, maps and sample bags. Meriden the Victorian vogue for natural history study, combined was a well chosen spot for their field camp, situated in with the persistent footwork of geologists and naturalists, sight of the spectacular traprock cliffs of the Hanging resulted in a wealth of knowledge about the unique Hills and Lamentation Mountain. Hiking to prominent outcrops that they would measure and map, the young Harvard geologists learned to inter­ pret the composition and form of the geologic features that they visited. By the end of a summer of adventurous climbing, prolific note-taking and friendly arguing, they were swept into the controversy over the formation of the ridges. They too became speculators on the order and timing of prehistoric events that had given rise to the landscape of the Central Valley of Connecticut and Mas­ sachusetts. These same traprock cliffs of Central Connecticut and Massachusetts still capture the attention of all who travel in the region. Interstate 91, which runs up the Central Valley, is graced with some of the best vistas of the ridges. They rise precipitously above the valley floor and West Rock-viewed from the west, circa 1890 are fringed by steep aprons of fallen rock, distinct from (The New Haven Colony Historical Society) lO qualities of the traprock ridges. Fascination with the Sound for over 100 miles to northern Massachusetts. It ridges has continued to be reflected in the work of ranges in width from eight miles near ew Haven to 20 geologists, ecologists and landscape artists to the pres­ miles at its broadest point. The elevation of the Valley ent day. rises from sea level to 300 feet, in contrast to the Up­ A relief map of Connecticut dramatically illustrates lands, which range from 300 to 1500 feet. The trap­ that the state is divided into three major regions. The rock ridges are sharp spines of rock running the length of Western Uplands are separated from the Eastern Uplands this otherwise modestly undulating Central Valley. The by the expanse of the Central Lowlands, or Central ridges protrude from the valley floor with elevations of Valley. The Valley trends northward from Long Island 500 to almost 1000 feet. Connecticut's major physiographic provinces. , These three major , 1 areas have distinctive ' geology, soil types Ea5ter~~.- and topography. Upla~d Lowlall.d ;' 11 The Eastern and Western Uplands are underlain pre­ dominantly by hard, erosion resistant rock such as schist and gneiss. In contrast, sandstones, shales and con­ glomerates found in the Central Lowlands are soft and susceptible to erosion. The exception are the ridges of the Central Valley, which are made of durable rock that geologists call basalt and most people know as traprock. Historically, the Central Valley has been the focus of intense land use and agricultural development because of the richer, deeper and more level soils found there. The traprock ridges stand out as a dominant feature running through the Valley. They punctuate the flat expanse, interrupting continuity ofland use patterns and lending visual drama to the otherwise gentle landscape. The ridges occur in the Valley in two major belts. The major central ridge is called the Metacomet Ridge and runs from Branford past Meriden, through Hartford and north to the Holyoke Range in Massachusetts. Near Meriden, the continuity of the Metacomet Ridge is bro­ ken up, with the Hanging Hills as a bridge between the northern and southern sections. At Bluff Head, in Durham, Connecticut, the southernmost part of this ridge system abuts the Eastern Uplands. A more frag­ mented but related series of ridges lies further to the west From the "chest" of Sleeping Giant and includes West Rock in New Haven, Sleeping Giant 12 The Sequence It is not easy to imagine the sequence of geological events that created the Connecticut landscape. Interpreting these events has stirred controversy among ew England geologists for over a century. New evidence has fre­ quently necessitated the revision of theories about the geologic origins of the region. Traprock ridges are a major and highly visible part of this geological story. The sequence of events that created the present land­ scape is solidly but cryptically recorded in the bedrock geology. It is there one must look to interpret the origin of the traprock ridges. Understanding of underlying bed­ rock structure is based on information gradually ac­ Looking north toward the Barndoor Hills cumulated from naturally exposed outcrops, blasted roadcuts and quarries, tunnels, well-borings and the explorations of prospectors, fossil hunters and natu­ m Hamden and the Barndoor Hills near the Massa­ ralists. The relationship between the surface forms and chusetts border. the underlying rock strata is an imaginative three dimen­ Despite differences in their formation, the ridges in sional projection pieced together from the interpretation both belts are similar in appearance. Most of the traprock of these features. Geologists constantly revise and en­ ridges in the Central Valley have similar aspects and large this picture with new insights and observations. slopes due to large scale processes that tilted the bedrock The now widely accepted theory of plate tectonics masses in common. Their steep cliffs generally face west describes the earth's crust as large plates of bedrock and dip gently eastward from their summits. Even to the floating on the underlying molten mantle. The plates casual observer, their uniform positioning links them as a move slowly, but with great force. Over hundreds of feature in the landscape of the Central Valley. millions of years, the plates have drifted, changing size 13 Late Paleozoic era: "New England Alps" created Early Triassic period: Beginning of sedimentation by lateral compression and position. Pile-ups have occurred as one plate ground crystalline rock. By the early Triassic period, some 75 into another, forming mountain ranges. The collision of million years later, this range had lost its youthful height plates and the resulting mountain-building is currently and ruggedness to erosion. The only evidence of these in progress in the Himalayas and Andes. After colliding, mountains left today is their roots, which constitute the some plates reverse direction and pull away from each bedrock of eastern and western Connecticut. other, trying the elastic strength of the earths crust. Such Over the next 90 million years, the motion of the plates a sequence of events marked the beginning of the forma­ changed and the North American and African plates tion of current landforms in Connecticut's Central Valley.