ASK A CONNECTICUT GEOLOGIST
Here are posted some answers to real earth science questions. If I don't know enough about the subject, I will forward questions to colleagues who can provide answers, which I will credit to them. I am also happy to respond to you personally if you wish, without posting the question and answer on this web site. In all cases the questioner will remain anonymous! Please submit your questions via email. Also see this web page for links to other ask-a-geologist websites.
Q: Where can I collect fossils in Connecticut?
A: Sorry to say, probably no place. Although we have rocks of many ages, only Mesozoic fossils (225 to 185 million years old) and Pleistocene fossils (less than 14,000 years old) are well known in Connecticut. Dinosaur tracks, fish parts, and plant fossils are actually fairly common in several places in the Mesozoic rocks of the Hartford basin. Unfortunately, most of these sites are along limited-access highways or even more-limited-access private property, where it has been difficult to get permission to collect. It would be a mistake for me to publish that information, because it might encourage trespass or safety problems. Also, fossil looters have already damaged some important locations by cutting out tracks to sell. Some marine and lake fossils (mostly shells) and a few large mammal bones have been found near the shoreline, or in bogs and lake-formed clay beds inland, all dating from the end of the Ice Age. I don't think those sites are accessible, but I will ask the state geologist if he knows more about that. Your best bet is just to visit the excellent collections on display at Dinosaur State Park in Rocky Hill, the Peabody Museum in New Haven, or the State Museum of Natural History in Storrs. If you insist on trying your own hand anyway, consult some of the references in the bibliography page (such as by McDonald or Colbert).
Q: What is the oldest rock in Connecticut?
A: There are some old gneisses in the Grenville "basement" of western Connecticut, which is also called "proto-North America." At the March 2002 meeting of the Geological Society of America in Springfield, John Aleinikoff and Gregory Walsh reported ion microprobe dates in the New Milford area as old as 1311 million years (1.311 billion years) for a granite gneiss, and several other gneisses are near 1045 million years, or the end of the Grenville Orogeny. Similar ages have been measured in the Hudson Highlands to the west and Green Mountains and Adirondack Mountains to the north, which have related rocks.
Q. Is part of Connecticut made of rocks from Africa?
A. Sort of. It is complicated, so bear with me here. The southeastern region of Connecticut is made of the Avalon terrane, which has Late Precambrian (about 550 to 740 m.y. old) gneisses that were originally an ancient volcanic arc along the northwest margin of what would later become Africa (then connected with "proto-Gondwana"). It was probably similar to the volcanic Andes Mountains of today's South America. This region broke away from Gondwana about 480 million years ago, before Africa was formed as a separate continent, and Avalonia moved across the Iapetus Ocean as an independent micro-continent before colliding with other terranes, and lastly into the present northeastern North America (part of a very old terrane called Laurentia). It was pushed farther inland when proto-Gondwana (Africa + South America + Antarctica) itself crunched into our continental region in Late Paleozoic time. This last collision ended about 280 million years ago, leaving a great fault boundary (the Honey Hill - Hope Valley fault zones) and scattered granites and pegmatites that were melted from the older Avalon rocks. Until the Early Jurassic, Connecticut and Africa, with the Avalon terrane sandwiched in between, were all within the super-continent of Pangaea. When the new Gondwana split off from what would become eastern North America, the north-central part of the Atlantic Ocean was opened and the western side of modern Africa was formed, but it left Avalonia behind. This same terrane runs in a narrow slice through the Avalon Peninsula of Newfoundland, where its name comes from, and also into southern Ireland and Great Britain.
Q. I am currently trying to gain access to any information available on the research being done by UConn at the open fault located behind 2992 Hebron Ave. Glastonbury Ct. Any information from the Boston geological expedition at the same site would also be helpful. If you could provide me with the info. or where to obtain it from, this would be of great assistance in my research into the lay of the land. Thank You.
A. Correct me if I am mistaken, but this must be the Minnechaug Farm hillside that the Town of Glastonbury bought to protect as Open Space. Prof. Gray of the UConn Geology & Geophysics Dept. took some geology students there last summer, as part of their field geology course. I once saw it with Prof. Wintsch of Indiana University, who had been studying that part of Connecticut and has published a description in a guidebook a few years back, which is available from the DEP bookstore in Hartford. You can also see the geologic map made by the UConn students posted on the wall in Beach Hall, in Storrs. There is no open fault there, but it is a highly deformed zone of the rock type called Glastonbury Gneiss (deformed hundreds of millions of years ago). Probably other geology depts. (such as from Boston schools) have taken students there during field trips. It is an interesting and educational location because of the rock structures.
Q. Hello, I am 42 years old and have lived in the Connecticut Valley (Southern Middletown), and now Newington, all my life. In fact, as a child, my family and cousins were among the first to travel on Rt. 9 South, we waited in the 'Grand Opening" ribbon cutting line (Gov. Dewey) for 2 hours before Dewey finally showed up, and then we drove the "new' highway to our cottage in Saybrook. Needless to say, I've travel 9 quite a bit!
Well, It took until this year before I began to wonder about the scenic rocks along 9.
1) Why are these rocks at an angle to the ground?
2) Why are different shaded lines in the rocks? (what are the 'white' black, etc. color differences?)
3) Why do I see students looking at these and the newer Rt. 9 rocks in Berlin area?
- Is there a 'geology' tour guide for the laymen, naming the locations and their significance? I'd enjoy walking about and learning what is so fascinating in my own area. Thank You
A. I take it you are referring to Rte. 9 near its intersection with the Berlin Turnpike, which is in the Connecticut Valley. These are 'young' rocks formed in Mesozoic time during the interval between 225 and 175 million years ago (50 million years, a very long genesis). The valley collected a lot of sand and gravel from streams and rivers, as well as mud from lakes that came and went over time. What you see in the roadcuts are these sediments after they were cemented by iron and carbonate minerals in the groundwater. Here are some answers:
1. The layers of sediment were formed horizontally, and only afterward became tilted about 10 to 20 degrees generally toward the east. This is due to a huge fault that defines the eastern border of the valley. The entire upper crust of the earth gradually dropped several miles downward along the western side of this fault, causing the tilt in the valley layers.
2. The light layers represent stream sand and gravel exposed to the air (sand colors that are also partly oxidized red), while the dark layers are lake muds that were under water deep enough to escape oxidation. Their alternation of layers is due to Milankovitch Cycles, which are changes in the tilt and orbit of the earth that repeat over 100's of thousands of years. This is an astronomical cycle that affects our climate, and the wetter periods made the lakes and dark mud layers. The dryer times reduced the lakes and allowed more stream gravel layers.
3. The roadcuts along Route 9 are famous among geologists, who visit them often with students (but often without official permission from the highway dept -- it is not always good to stop on limited access highways). Great places to teach geology. You can see some of these same rocks safely behind the new Target stores at Buckland Hills and also up the hill west of Meriden Square Mall.
There are several field guides published about these rocks, available in the DEP bookstore at 79 Elm Street, Hartford. I am working on a book for the state DEP called "Connecticut in the Mesozoic World," which will have a lot more descriptions and information that is designed for teachers and the general public.
Q. I am aware that Gondwana was an old Indian State (near Bhopal), which was once controlled by the Gonds who spoke Gondi. I am also aware that one of the specimens of Glossopteris was discovered close to there & may have had something to do with giving Gondwana(land) its name. But who bestowed the name? I understand it was once called 'Nothogaea', if so was there once a 'Boreogaea?' I believe that Brogniart had something to do with it when he first described the Glossopteris - was he the one who coined the name?
I would be most grateful if you could tell me where to pursue this line of enquiry!
A. Nancy McHone, at the state geologists office, provided me with the following:
"According to the Glossary, Gondwana 'was named by Suess for the Gondwana system of India, which has an age range from Carboniferous to Jurassic and contains glacial tillite in its lower part and coal measures higher up. Similar sequences of the same age are found in all the continents of the hemisphere; this similarity, along with much compelling evidence of other sorts, indicates that all these continents were once joined into a single larger mass.'" So, there was already a group of rocks in India with that name, and you are correct about Suess as the originator.
Also, I looked up Gondwana in a geo history book called "Debate About the Earth" by Takeuchi, Uyeda, and Kanamori (1967, Freeman Pub). Prof. A. L. Du Toit, an early proponent of continental drift who worked at Johannesburg University in South Africa, proposed that there were once two super-continents rather than just one "Pangaea." The southern one included South America, Africa, Australia, Antarctica, and strangely enough, India (based on Glossopteris and other fossils, apparently). Du Toit wrote about this in his 1937 book called "Our Wandering Continents" (Edinburgh, Oliver & Boyd Pub.). The Indian connection led to the use of Gondwana, while the northern continent was named "Laurasia." Gondwana (also called Gondwanaland) and Laurasia were connected for a while around the western side of the ancient Tethys Ocean, which made Pangaea as well. Du Toit was amazingly accurate, considering it was only the 1930's.
Q. Hi, I read your paper on the flood basalts and visited the website on the terranes in Connecticut and I was hoping that you might be able to clarify something for me. I live in California along the coast and I have been readingAssembling California by John McPhee and Roadside Geology of Northern and Central California by Alt and Hyndman. I am struggling to understand the formation of basaltic dikes in the oceanic plate junctions. Both of their descriptions are vague and I haven't been able to find a decent explanation on the internet. Any and all assistance that you can offer will be heartily received. Thanks a million.
A. It won't cost you that much. Where plates are separating in oceans, the ocean crust splits within the central rifts of the mid ocean ridges. Each crack may be dozens to hundreds of of kilometers long, and extends through the crust into the mantle (which is fairly shallow near ridges, maybe 20 km or so deep). The mantle melts at the base of each crack and the liquid basalt flows upward, often oozing out on the ocean floor at the ridges. This is a dike, which solidifies pretty quickly (probably in a few days to months). The actual process is rarely observed because of the remoteness of the locations, except in Iceland. The cooled dikes become new ocean crust, so the ocean plates grow larger in both directions perpendicular to the dikes (and mid ocean ridges). The crustal enlargement by dikes causes the slow movement of diverging plates. On continental land, dikes also form because the crust and upper mantle are being pulled apart, but here the depth to melt zones in the mantle is typically much greater (60 km or more), requiring a more unusual and extreme tectonic event. When liquid basalt does reach the land surface in dikes, the fissure eruption can be much more violent than what we see in the ocean depths, due to the much lower pressure of the air versus the deep water. Also, the lava cools more slowly on land and can generally flow much farther (although there is some question about this). You might examine the well-done digital geology book available on the USGS web:http://pubs.usgs.gov/publications/text/dynamic.html for additional illustrations.
Q. Tell me about the "Great Unconformity" in the Roaring Brook Ravine near Southington, CT. Thanks,A. The Great Unconformity in Roaring Brook exposes the basal conglomerate member of the Triassic New Haven Arkose of the Hartford basin, in contact with the Devonian Straits Schist of the "basement" beneath the Mesozoic rocks. The time gap between the two formations is about 170 million years (from about 390 to 220 m.y.). A lot happened to Connecticut during that time gap, including two major metamorphic events, the Acadian and the Alleghenian.
There are only a few exposures of this unconformity because most of the western border is formed by the Mixville fault, which has dropped the unconformity down and below the surface along the fault. The conglomerate contains a small amount of locally-derived schist and also many pebbles and cobbles of rocks carried in from the west and possibly east. The image for that time is of a wide plain becoming covered by stream gravels and larger rocks washed down from hilly areas that may have been some distance (dozens of miles) away. The arkose materials have been used in arguments of "closed basin" versus "broad terrane" models for the Mesozoic basins, but similar basal conglomerates might form in either environment.The location is on private property and is not accessible to the public. I understand that the Southington Land Trust or the town might be interested in obtaining the land or public access rights, which would certainly be good for earth science fans.
Q. I was wondering where a good place to go would be to see modern sedimentary environments, ancient sedimentary deposits, or rocks affected by mountain building that would be near me. I live in East Lyme, CT and would like something close by. Is lantern hill considered one of these? Please let me know, thanks
A. Some of the rocks around East Lyme and Lantern Hill might have once been sedimentary, but they are all completely metamorphosed by heat and pressure now, so you will not find what you are looking for. Modern sediments are forming at the shoreline and in streams and rivers, and sand and gravel quarries all display sediments concentrated by the glaciers at the end of the last ice age. The Mesozoic sedimentary rocks of the Connecticut Valley are still in good shape and provide excellent opportunities to study sedimentary environments. I recommend that you start by spending some time at Dinosaur State Park, where there are good explanations of how Mesozoic sediments formed in Connecticut. You should also consider attending one or more of the public field trips offered annually by the New England Intercollegiate Field Conference (www.neigc.org) -- the next one will be next October. Several past field guides describe the sedimentary and metamorphic rocks of the region. You can get them at your library or from the state DEP bookstore in Hartford.
Lantern Hill is a thick body of quartz (silicon dioxide) formed along a Mesozoic fault, which continues to the north and south. The fault broke through several terranes of older metamorphic rocks that were affected by the mountain-building event called the Alleghenian Orogeny, which was caused by the last collision of crustal plates near the end of the Paleozoic Era (about 300 to 280 million years ago).
Q. I am interested in learning more about the geology of CT. Do you know of any written material that describes roadside tours of exposed geological formations in CT.
A. There is a book being written by Father Jim Skehan of Boston College on the roadside geology of Ct (and RI), which might be out in 2004. It will be very useful -- I know him to be a very good geologist and writer. You could also sign up for the next annual New England Intercollegiate Geological Conference (NEIGC), which will have some Ct. area field trips next October. Students and the public are welcome -- see their web site at www.neigc.org. Several previous field guide books for Connecticut are available at your library or for sale at the DEP book store in Hartford.
Q. Hi. i am looking for a map of connecticut that has the three types of rocks on it.... but it is impossible to find. I need it for 1/9/03....which is today!! i need it because we are mapping where rocks are found in connecticut... do u know of any rock websites that might have maps... if not... can u tell me a few places of where sedimentary, metamorphic and igneous rocks can be found!! thanks...hope to hear from u soon.
A. "U" can look at the simplified version of the state geology map on the ctgeology web site. It has all three groups of rocks on it, although you may need to know the names of some of them. More details are available from local geology maps published by the Talcott Science Center web site. There is also some explanation of the rock types on that website. If you had more time, you could see some of those maps and books about them at your library, or buy them at the Hartford DEP bookstore.
Q. Hello, Hopefully, you can help us. We are a group of community members very concerned about the "Mixville Fault" in the New Haven area. This fault supposedly runs from New Haven through Woodbridge and there has been some "rumblings" about noxious gases. Can you enlighten us at all or direct us to further research? Thanks so much!
A. Yes, I have read about the geology of the Mixville fault. This is the "western border fault" of the large Hartford basin, which formed in Mesozoic times through central Connecticut and Massachusetts. There is no evidence of earthquake activity for this or most other faults in Connecticut since at least 100 million years ago (Late Cretaceous). Earthquakes in Ct. are generally small, rare, and are not located on known faults such as this one, and our personal risk overall is low.
The only dangerous gas that the Earth (at least in Connecticut) emits is radon, which is colorless and odorless, and radioactive. Radon continuously forms radioactive daughter elements, which can stick to the inside of your lungs and cause cancer. The gas comes up in well water and fractures in the earth, which might include the Mixville fault, but actually, faults and fracture systems are common everywhere and can be conduits for radon. I doubt that the Mixville fault is a worse culprit than any of the other Mesozoic faults in the state. Radon is generated from uranium, which has an irregular distribution, so you cannot predict which houses will get more radon than others. The gas can seep into houses directly from those bedrock fractures into basements, but more commonly it comes from well water (at shower heads, etc.), because it also gets into the water deep underground. Surface reservoirs and shallow wells generally have no appreciable radon, but urban houses can still get it from the earth directly.
A large percentage of houses in Ct. have levels that are above the EPA health guidelines, which is why ALL houses in the state should be tested for radon. It is cheap and easy to do so. If you find high concentrations of radon in your air or water, there are several reasonable ways to reduce it, so no one needs to think this is a disaster or something that will reduce the value of their house if it is found. My concern is mainly about lack of interest and awareness of this problem. For example, many schools have not been tested. You can find out more about radon from both the Ct. Dept. of Health (http://www.dph.state.ct.us/BRS/radon/radon_program.htm) and from the US EPA (http://www.epa.gov/radon/).
Q: Can you explain the rock formations in the 63 acres of Ridgefield town open space off of Cooper Hill Road? It's a combination of hills, swamps, and many outcrops. What types of rock is it? How old is it? Also, is there a field guide that would describe the rock formations of Fairfield County? Thank you.
A: I went to MapQuest (http://www.mapquest.com/) to find Cooper Hill Road and then to the state geological bedrock map. The geology of Ridgefield is wonderfully varied, including several terrane boundaries in the northern part of town. It looks like the road is in Oh, or Ordovician Harrison gneiss, which is "dark to light gray, foliated" and its Paleozoic age might be about 460 million years old or so. Not far away is Og, or "light colored granite gneiss" about the same age or younger.
There is a field guide published for the Bethel area a little farther north, in the 1985 NEIGC Guidebook No. 6 available from the state DEP bookstore in Hartford. You can check with the bookstore (http://dep.state.ct.us/store/) to see if a quadrangle geology bulletin and map is available for Ridgefield, which might be fairly technical but would give you a lot more detail. You might also ask the New York State Geological Association (http://nysga.net) if a field trip guide to your area is in one of their books (they sometimes stray across the border).
Natural ledges and outcrops of hard rocks like these have been sculpted by the glaciers during the recent Ice Age, as you probably know, and sediment from the glaciers has filled and disrupted the previous surface drainage patterns, thus creating the many wetlands, swamps, and ponds of New England.
Q: I am an earth science student in Avon. I am having a lot of trouble finding out exactly what rocks are in the different terranes and how they got there. I need this information for a project. Thank you very much if you can help.A: Hello, I assume you mean the rock groups, which in Connecticut are nearly all metamorphic, except for the sedimentary and igneous rocks of the Connecticut Valley terrane. We have hundreds of formations that are each distinguished by differences in textures and minerals. You need to examine the state bedrock geology map to see brief descriptions of each formation.Much of this detail can be found at the bedrock map on the web published by the Talcott Science Center (http://tmsc.org/geology/bedrock/bedrock.htm) and as summarized in the book called "The Face of Connecticut" by Michael Bell, also on the same web site (http://tmsc.org/face_of_ct/185.htm).The northwestern terrane is sometimes called "proto-North America" and it contains Early Paleozoic marbles and quartzites, sitting above or against Precambrian gneisses similar to those in the Adirondack Mtns. Most of the state is made of several terranes of schists and gneisses that were derived from Iapetus Ocean sediments (mostly various silts and muds) and volcanic rocks of that ocean, also formed in the Early Paleozoic. The Connecticut Valley terrane is built onto these Iapetus rocks, and consists of sandstones, mudstones, and lava flows of Early Mesozoic age. In southeastern Connecticut, the Avalon terrane was pushed as a thick metamorphic layer beneath the Iapetus rocks. The exposed portions of Avalonia include gneisses that look like Iapetus rocks, as well as pink-colored gneisses (formerly granites) that characterize this terrane. The Avalon rocks have a Late Paleozoic metamorphic age but the original rocks are much older, up to 600 million years old.You can see many of these terrane rocks along highways throughout Connecticut.
Q. Dear Greg, My question actually pertains to an area in Pennsylvania not Conn. I hope you can answer my questions.I recently discovered a granite gneiss hma aggregate plant near a house that I have a deposit on. I am relocating to the area and did not realize the site existed until yesterday. The parking lot is about a quarter mile from the house and the mining site about a half a mile from the house. Apparently the granite gneiss is used in the asphalt mix made at the plant.Are you aware of any associated health risk with such an area?
A. Hello, there should be no health risk unless dust from the quarry reaches the house, or if they have polluted the ground water (assuming you will use a well). Rock dust is bad for your lungs, more so than most people might realize. But if the quarry uses good dust abatement procedures, as it is supposed to, there should be no problem for its employees or the neighbors. Ground water pollution can occur from spills or leaks of fuels and cleaning agents, etc., and will show up in a good water test. Sometimes you can smell gasoline in the water, but not always other pollutants. Of course, there might be other concerns such as noise from the quarry or heavy truck traffic -- you will have to judge that.
The owner should provide you with a recent well water test for likely pollutants, unless it is on a public system of course. You should also see a test for radon in the house air, which can occur anywhere but is more prevalent where there are granitic rocks. This is not hard to do and a fix for high radon is not difficult either (maybe a few hundred to a few thousand dollars, typically), so it should not stop you from buying a house. Some states require a radon test any time a house is sold, and the owners could do this for you at low cost. Then any fixes could be negotiated up front and everyone stays satisfied.
Q. I am curious about the history of Lantern Hill in Ledyard, CT. Do you know anything about it? Can you suggest a site or book which might be of help?A. Yes, but I have really only heard about its geology more than its human history. This hill is in an interesting area of nearly pure silicon dioxide (quartz) that has replaced the older rocks along a fault zone. It was mined for many years by the U.S. Silica Company and earlier companies, but the Pequots bought it and closed the mine. Lantern Hill has special significance to them. The geology of Lantern Hill was the subject of a PhD dissertation a few years ago by Robert Altamura, who can be reached at email@example.com. Bob wrote about it in a field guide chapter published by the state geological survey, and available from the DEP bookstore as Guidebook Number 7 (1995).
Lantern Hill's human history is also given a few pages in "Legendary Connecticut" by David Phillips (Curbstone Press, 1992). Your library might have these books, and the Phillip's story is on the web athttp://www.curbstone.org/index.cfm?webpage=69. Using Google I also found a website for cliff climbing at Lantern Hill (http://users.ids.net/~brianps/lantern.htm).
Q. How much will Pike's Peak erode over one million years from today. Just an estimate. FOR A SCHOOL PROJECT!!! PLEASE REPLY ASAP. Thanks
A. Hello, in a dry but frosty climate of our western mountains, a fast erosion rate might be about 0.1 mm per year, or about 100 meters per million years. A hundred meters is about 330 feet. Erosion rates for mountains vary a lot, maybe between 100 and 600 feet per million years, but at the same time as it is eroding, the mountain might also be rising or sinking for other reasons. Also, as the mountain gets lower, the erosion rate will slow down. By the way, in the East, the Great Smoky Mountains appear to be eroding about 20 m per million years, or about 2 kilometers (6600 feet) since the middle of the Cretaceous Period. I HOPE THIS WAS QUICK ENOUGH!!!
Q. Dear Mr. McHone, I ran across a site in where you and/or your colleagues were answering questions about Connecticut geology. I am not sure if you are still doing this, but if you are, I have questions about the Gaillard Graben. I would like to know what it is, how it was formed, it's boundaries, and how one can see it today. If you could provide information about the Graben, or steer me to some information, I would greatly appreciate it. Thank you for your time!
A. Hello, yes, the Mesozoic Gaillard graben is a section of the southeastern Hartford basin, north of East Haven. It is defined by its own faults and a synclinal folded structure, and it is large enough to drive through on several roads. The graben is clearly shown on the state geological map (check out my version on the front page of the CtGeology web site). This structure was studied by the late John Sanders, and there are two of his publications that you can obtain from the state DEP bookstore in Hartford (http://www.dep.state.ct.us/store/), or a library. Although he describes it as Triassic, we now know there are Jurassic strata as well. The graben appears to have formed mainly after the Early Jurassic basalts layers, by folding from differential movements along several faults that cut across the big basin, and possibly by compression as well (this process, called inversion, is an important new proposal for the later history of the basins).
Sanders, J. E., 1970, Stratigraphy and structure of the Triassic strata of the Gaillard Graben, south-central Connecticut: State Geol. Nat. Hist. Survey Conn., Guidebook no. 3, p. 1-15.
Sanders, J. E., Guidotti, C. V., and Wilde, P., 1963, Foxon Fault and Gaillard Graben in the Triassic of southern Connecticut: State Geol. Nat. Hist. Survey Conn., Rept. Invest. n. 2, p. 1-16.
Q. Hi Mr. McHone, I got your e-mail from the UConn website. I’m a freelance photojournalist, and I’m researching a story idea. I thought I had read somewhere that a small gold deposit had been discovered in Connecticut in the last few years. Any truth to that rumor?
A. Hello, yes, tiny bits of gold flakes are sometimes found in streams in various spots around the state. Some of those places are described in a book or two on panning for gold, which I have seen for sale at Nature's Art in Salem. Also, you might be interested in some of the stories on the "Megaliths, caves and other interesting stuff" web site, including a page about a gold stream in Litchfield County:http://members.skyweb.net/~channy/dutchy.html
I have been on a field trip to the place in Cobalt (a village in East Hampton) on Great Hill, where gold was found in a quartz vein in the 1980's by Prof. Norman Gray and his students at UConn (the same department that has recently been slated for abolishment, one of the worst decisions ever made by their university bureaucrats). I understand that the mineral rights were soon bought up by a mineral company, but nothing ever came of it. Most likely, the vein is too small.
Here is a short description about the Cobalt area written by Prof. Jelle de Boer of Wesleyan University (this is his work, and you will need his permission to use it).
Q. The reason for my inquiry is that some students asked me if there were any kettle lakes in the Eastern part of Connecticut, specifically whether Crystal Lake in Ellington and Mashapaug Pond were examples of kettle lakes or ponds. We are currently studying glaciers and in discussing the last ice age, and have tried to include local topological features in our discussions and try to answer their few questions.
I am not familiar with Connecticut geological details. I was very happy to discover the "ask a geologist" icon on the Wesleyan geology website. I'd appreciate anymore help you could give me about Crystal Lake in Ellington and Mashapaug Lake (or pond) in Union...thank you for all your effort and help.
A. I passed your question on to Prof. Clebnik of ECSU, who replies:
"For the two specific lakes of interest to your students, I had to consult both geologic and topographic maps for an answer. As you may know, kettles are commonly associated with stratified drift (the meltwater-deposited sediment generated mostly in valleys as the last ice edge retreated northward). (A) Crystal Lake, Ellington: This lake straddles two quadrangles--Ellington and Stafford Springs--for which surficial geologic maps have been published. Stratified drift is shown along both the S and N parts of the lake. Thus, it appears to me that a block of ice occupied the area of the lake for awhile. (B) Mashapaug L., Union: It occurs on the Wales, Mass./Ct quad. A bedrock but not a surficial geologic map has been published of that quad. I looked at the topographic map to interpret what might be stratified-drift related landforms. I also examined the bedrock map to see where rock outcrop occurs near the lake. From those sources it appears that there may be stratified-drift features along the NW to N and also the S side of the lake. It's harder to be sure on this one, but I'd lean toward the lake basin having been occupied by a mass of stagnant ice at one time. You may be able to access via computer (with broadband connection--not ordinary phone/ modem hookup) a web site at ECSU. I collaborated with a colleague a few summers ago in creating a virtual tour of glacial-related sites in the Willimantic area. The site address is: http://www.easternct.edu/%7ehyattj/ If other glacial puzzlers pop up, I'm happy to help out." Sherman Clebnik, Environ. Earth Science Dept., ECSU, Willimantic 465-4323 or firstname.lastname@example.org
Q. I have another geology question for you. Were the Hartford Basin and the Newark Basin (New Jersey) one continuous basin with the Pomperaug Basin being a remnant? What's the latest theory? Thank you.
A. Hello, this one has gone back and forth during the past 110 years. For most of that time it was generally accepted that yes, the basins were originally continuous, until several distinguished sedimentologists in the 1970's and 80's argued that what we see today is close to what has always been. I disagree with that. When we restore the strata to thicknesses they had before erosion, and rotate them back to horizontal before Jurassic-Cretaceous border fault motions, the Newark and Hartford basins probably were connected across areas that are now southwestern Ct. (including the Pomperaug basin) and western Long Island, although not into NW Ct. There were more regions under Mesozoic rocks to the east as well, possibly across the Gulf of Maine into today's Fundy basin, and similar sediment layers surely ran south and west of New Jersey.
Lava flows of the same magmas we see in Ct. covered all of these regions as well -- my main contribution to this debate. A few fine petrologists support my view, but there is still vigorous disagreement from some strat/sed folks. This "broad-terrane" picture is probably good for Triassic and beginning Jurassic times, but tectonic uplift really got going in the Jurassic Period, so the basins were soon separated by erosion of the regions between them. Also, there were certainly basement hills sticking up around and between the early super-basins through this time, from which coarse gravels and stones washed down mountain valleys as Jurassic alluvial fans.
I have described some of this in my new book to be published by the state DEP in 2004, called Connecticut in the Mesozoic World.
Q. Connecticut has quite a few metamorphic hills which are formed at least in part from ancient sea sediments. Is there or could there be any shale mixed in among these rocks which might contain some dried oil or even pockets of liquid oil? Thanks.
A. Hello, there might have been some oil in our Iapetus Ocean rocks while they were still sediments, but the process of metamorphism involved such high heat and pressure that the hydrocarbons were all destroyed. Oil and gas exploration people put a lot of effort into finding the maximum temperatures that rocks have been subjected to, to help decide if they are worth drilling. Our sedimentary rocks in the Connecticut Valley and Pomperaug River Valley actually do have tiny amounts of coal, oil, and gas, and some companies have evaluated them, but mostly these rocks have been overheated as well and are not considered likely to have economic amounts.
Q. Is the CT Valley considered strictly Triassic or are their other opinions developing that is a cross?
A. Hello, up until the 1970's people thought that all of the Mesozoic rocks of the Connecticut Valley (which geologists call the Hartford basin) were Late Triassic in age. You will see many references in the older literature to the "Triassic" basins and its rocks. However, in 1969 Jelle de Boer at Wesleyan showed that the magnetic directions of the upper layers are different from the lower layers, and in 1977 Bruce Cornet finished PhD work at Penn State in which he proved that the younger sediments (between and above the lava flows) have Early Jurassic microfossils. We now know that lava flows in the basins of eastern North America are all the same age (where they are preserved), so sediments below them are all Late Triassic, and above them are all Early Jurassic, everywhere (even in Morocco). According to Paul Olsen, the Triassic sediments of the New Haven formation were deposited between about 220 to 201 million years ago, the Early Jurassic lava flows formed 201 to 200 million years ago, and Early Jurassic sediments of the Portland formation above them continue up to about 192 million years ago. More than a mile of younger Jurassic sediments have been removed by erosion.
It is hard for everyone to keep up with these developments, so you might see some other ages still stated in the literature. The latest ideas have been published recently by Columbia University Press in two volumes (listed on their web address: http://www.columbia.edu/cu/cup/catalog/data/GEOLOGY534.HTM).
Q. Dear Greg, I was wondering if you could recommend any papers or articles that discuss the geology of southeastern Connecticut, specifically the area around the Thames River basin. Most people I've spoken with have told me that the reason why there isn't much on the area is due to the complicated nature of the metamorphic rocks (Avalonian terrane). I've recently read the "The Face of Connecticut" and an article entitled "Geology of Connecticut". Could you suggest anything else that discusses the local geology in terms of the tectonics?
Thanks, P.S. The Wesleyan Connecticut Geology website is awesome!
A. Hello, the Avalonian terrane is somewhat controversial in origin and makeup, but it is not especially complicated in Connecticut. There have been a few recent suggestions that it should be subdivided according to new work in Atlantic Canada, where the terrane (or group of terranes) has other features, and also new work concerning the ages of its minerals and metamorphic conditions.
Most recent studies of eastern Ct. geology have been spearheaded by Prof. Robert Wintsch of Indiana University. He has several good technical papers and also some field guides that you can buy, or find in your library. See some of the NEIGC field guide books listed at http://neigc.org/NEIGC/Guidebooks.html . Bob Wintsch has papers in the 2003, 1998, and 1993 (GSA) books.
I also like the book by Raymo, Chet and Raymo, Maureen E., 2001: Written in Stone: A Geological History of the Northeastern United States (2nd Edition), The Globe Pequot Press, Old Saybrook, CT.
Thanks for the compliment and good luck.
Q. Hello Greg, I would like to know more about the volcanoes around the Holyoke range. I understand this area was especially active (sometimes violent) during the early Jurassic. I've read about "nested volcano cones" north of Mount Hitchcock. Are the small hills- Big and Little Tinker- part of these cones. I appreciate any info you can provide about this interesting area. Thank you!
A. Hello, yes, the Holyoke range is made of the same lava flows that we have in the Connecticut traprock ridges (except our Talcott basalt is missing), although I am not personally familiar with many Massachusetts locations.
Some local geologists used to be confused about the nature of the eruptions that formed these lavas, which were later tilted to create the hills. There are not volcanic mountains that people know from most modern eruptions because these were fissure eruptions, but some hills likely were formed from ash and lava that concentrated in spots along the fissure, which commonly happens at modern fissures. One of my favorite fissure eruption photos is of the "Krafla fires" of Iceland from the 1970's, a copy of which I posted at http://www.auburn.edu/academic/science_math/res_area/geology/camp/Fissure1.jpg. You can see how crustal fractures are feeding long lava fountains, and the lava is pouring out over the landscape. This is what Ct. and Mass. looked like 200 million years ago, at the beginning of the Jurassic Period.
To see what ash and spatter cones might have looked like where they have broken through the flows, go to http://www.geology.sdsu.edu/how_volcanoes_work/Fissure.html. There were probably similar features in Massachusetts during the eruptive cycles, and some parasitic volcanic spatter cones may still be visible even though surrounded by eroded lavas. The scale is different in that our eruptions were hundreds of times larger than any known in historic times.
Q. Hello, I am a student currently enrolled in high school right now, a junior to be exact. With my high school career coming to a close and decisions to be made about college coming up, I just wanted to know a few things about geology, which I happen to be interested in.
First off, I was curious about what type of math geologists deal with. I do fairly well in my math classes, being enrolled in our Honors program for the past three years and maintaining a steady B, and I just wasn't sure how difficult the math is that you use. Math doesn't come very easily to me, but if I work hard as usually do I can grasp the concept just a little later than the others in my class.
Secondly, I wanted to know what kind of a salary a geologist makes, and what level of college education I should get to make a good living. If you could just provide me with a list of recommended courses to take, and what a good college to go to for geology, I would be very thankful.
Finally, I wanted to know where a geologist would most likely find himself employed. Would it be somewhere here in the States, or does it depend on what I specialize in and whom I would work for? I find myself also interested in studying ancient structures, such as the pyramids and the old Mayan ruins.
If you could provide me with the answers I am looking for, I would be extremely grateful. As I am sure you know from your own experience, looking for the right career and the right college can be quite a daunting task. Anything you can do to help will be greatly appreciated. Thank you for your time.
A. Hello, you have good questions. I can help with some but not all of them.
For math, most of the time you will need to apply fairly simple algebra, plane geometry, and statistics. Hydrologists, geophysicists, and theoretical research people may also use calculus in some of their work. Skills with reading and making maps are helpful (now including simple GIS), and software such as MS Word, Excel, graphics such as Adobe Photoshop, and presentation Powerpoint are widely used in geology. None of it is especially difficult and most people gradually learn everything they need over several years. You will have time and opportunity to improve math and computer skills as part of your college geology work. I can tell from your email that you understand the need to show competence with writing (you don't need to win a prize, but use good organization and spelling).
Unlike the other sciences, a master's degree (usually two years of graduate work after your bachelor's degree) is considered the professional level needed for a career, although many private consultants have done fine with just a bachelor's degree. A PhD is expected for higher-level research work, top administrators, and for four-year college teaching (which usually also requires independent research). High schools and community colleges generally only require a master's degree for their teachers.
In my opinion a small geology department, either public or private, is a good choice for a bachelor's degree. The department should have at least 6 or 7 full-time faculty members and a good selection of course offerings. Your graduate work (master's degree) needs a larger program that has various research projects, and strength in specialties such as hydrology or geophysics. Also, look for a program that does a lot of field trips and field geology training -- even if you don't do field mapping you need to understand what it involves. Don't believe any hype about elite private or ivy-league schools providing a better education -- in geology, most of the larger public universities have good or better than average teaching and training in geology, and professional geology employers know it.
Geologists often feel like they are getting paid to have fun -- that is, their work is really interesting and enjoyable, and they look forward to the new projects that are always coming along. Many like to do a mix of office, lab, and field work, according to personal interests and abilities. The average professional company geologist salary is slightly above $100,000 per year, but many who work in universities and as state employees make less than that. You might expect to start at about $40,000 to $50,000 if you have a graduate degree.
Many U.S. geologists travel several times a year for a few weeks to a few months, both within the country and far away. You may have some choices about that, but of course the work often requires it. If you want stay near home every day you could specialize in GIS or laboratory work rather than field expertise. In Connecticut a lot of geology work is related to environmental problems, engineering, and water issues performed by consulting companies. The larger companies might send you into neighboring states for various projects.
The next biggest job area is with energy (oil, gas, and coal) companies, mainly out west. Those geologists are well paid and treated very well but job security has not always been very good. Otherwise, there are many positions in state and federal government, in colleges and universities, and in teaching high school earth science. Teaching duties can easily take up about all of your time but can be satisfying, so long as you can deal with the stress.
To see about geology careers use the internet, especially by American Geological Institute (http://www.agiweb.org/), and their page of links to career information (http://www.agiweb.org/career/carelink.html). Also see this website of geology jobs: http://www.earthworks-jobs.com/. AGI publishes a directory of geology departments that will be helpful in assessing their value for your interests.
Best of luck, and stick with this -- you will be glad you did.
Q. Dr. McHone, I'm going to be spending much of this summer in western Litchfield County (Warren, CT), and I really want to poke around the area rocks. Problem is, I haven't been able to find a good published guide to the geology of the area, or even that much info online.
Anyways, I was wondering if you could point me to any info about the geology of the area. Since I'm between schools, I can't access any journal articles (big bummer), but if you know of any cool places/roadcuts/streambeds/mineral collecting sites that are worth looking at, that would also be great.
Thanks very much.
A. Hello, there is not a lot written about Litchfield County geology, as far as I know. There is a little bit in my new book called Great Day Trips to Discover the Geology of Connecticut (Wilton, Ct., Perry Heights Press, 207 p.) -- go to http://www.cttrips.com/ for info. I also recommend Raymo, Chet and Raymo, Maureen E., 2001, Written in Stone: A Geological History of the Northeastern United States (2nd ed.): Old Saybrook, Ct., The Globe Pequot Press, 163 p.
A couple of web sites come to mind: http://www.angelfire.com/ct/litchfield/geology.html is privately published, and http://www.lastgreatplaces.org/berkshire/geography/art6358.html is by the Nature Conservancy, and appears to be well done.
You might be able to collect minerals that include our famous garnet in Roxbury (check out Green's Farm Garnet Mine), and I also recommend a visit to the Ct. Mining and Minerals Museum in Kent -- it is close to the Kent iron furnace and also Kent Falls, both of which are also worth a geological visit.
Q. Dear Greg, I live in Torrington, Ct. I am a beginner rockhound. My limited excursions in the Burr Mountain area suggest that we have a wide variety of glacial till materials which I would like to identify. The books in the Torrington library have not been much help. What do you suggest? And where would I be able to purchase any required tools? Thanks.
A. Hello, see the previous question and answer, but I have found another source of geological descriptions. Dr. Charles Merguerian of Hofstra University has produced many good field guides to geology in the northeast, available from him for a modest charge. He has several for western Connecticut. Check them out at http://www.dukelabs.com/On%20the%20Rocks/LocalityListBlurb.htm
Glacial till is pretty monotonous stuff. Your might be able to identify such materials using the Ct. surficial map and the Quaternary geologic map, available from the state DEP bookstore in Hartford (also check their website, http://www.whereeverythingis.com/depstore/). The store has mineral i.d. books and kits for sale as well.
Interesting rocks and minerals are everywhere in the state and I am sure there are good places to find them near you. Take care to collect only where you are sure it is allowed, whether on private or public property. I have a section that describes the tools and gear you will need near the end of my new book, called Great Daytrips to Discover the Geology of Connecticut, published by Perry Heights Press (visit http://www.cttrips.com/). Get a rock hammer from a place like Natures Art in Montville (http://www.enaturesart.com/) or a masonry hammer from a hardware or home store will be OK (do not use a nail hammer). Be sure to use eye protection. Also, consider joining a gem and mineral club -- check the list of clubs I have posted on the geologic web sites page. They will welcome you and provide tips for good places to collect minerals, plus they sponsor some trips. When you have a few hours, drive up to visit the wonderful Ct. Mining and Minerals Museum on Rte. 7, just north of Kent. You will find a great collection of local specimens.
Q. Hi, Greg. I attended a talk by Brendan Hanrahan last night in Cheshire and thoroughly enjoyed it. It was very informative and interesting. If I don’t get the two Daytrips books (yours and Brendan’s) for the holidays, I’ll be buying them for myself. I’m a hiker and have been reading about Connecticut geology recently. I found your site last month and passed it on to a few of the teachers here in Middletown, where I have been a technology facilitator (IT department) for the past two years. It is a great resource. Thank you for your efforts.
My question deals with identifying Connecticut rocks. I’ve read about the geological history of Connecticut, mainly in the Face of Connecticut and other books, but I would like to learn more about identifying rocks. I flipped through your book last night and it looks like it will be helpful to me with some of the pictures and callouts. I started reading a field guide, but it is a little over my head right now. For example, I started reading about the foliation of gneiss vs. schist and wasn’t able to completely understand. I need some more background information. Is there a book you could recommend for a novice such as myself? My wife is getting me the geological bedrock map from the DEP store, and I’d like to be able to identify rocks more readily when I’m out hiking or checking out rock cuts along the highways as I drive around Connecticut.
Any help you could provide would be great. Thanks.
A. Hi,, it is great to have you interested. I think everyone should recognize and be able to name the common types of rocks, just as they should for the most common trees, birds, mammals, etc. But it is certainly confusing for anyone who has not had some introduction to the subject, especially for those metamorphic rocks and mineral textures like banding and foliation. The bedrock map has a legend (in tiny type -- get out your reading glasses!) that briefly describes every rock formation on the map, in alphabetical order.
The DEP bookstore also has a naturalist's handbook guide to geology that is supposed to be pretty good. See http://www.whereeverythingis.com/depstore/index.cfm?fuseaction=shoppingcart.builditem&Product_ID=63 for that. There are some good websites as well, such as http://www.em.gov.bc.ca/Mining/Geolsurv/Publications/InfoCirc/Ic1987-5/intro.htm and http://www.rockhounds.com/rockshop/rockkey/ andhttp://geology.about.com/library/bl/blrockident_tables.htm?nl=1
The last one is on Andrew Alden's "About Geology" website (http://geology.about.com/), which is also on a weekly email newsletter that you can sign up to receive. He is an excellent educator and there is a big library of geology topics on the website where he explains things very well. I recommend it. Good luck.
Q. I was told once that there is a fault where Africa and North America abut along the western side of Prospect Mountain Road in Litchfield. Is this possible? Thanks.
A. Hello, no, the boundary where rocks like those in western Africa remain as part of North America is in southeastern Connecticut. The terrane of "African" rocks is called Avalonia, and it is the group of formations with lavender colors on the Ct. bedrock geology map (see the version I have on the cover page of this web site: http://www.wesleyan.edu/ctgeology/images/CtGeoMap_big.jpg).
On the map, major faults (which include most of the terrane boundaries) are shown as heavy black lines. The terrane boundary faults you see in Litchfield separate rocks of the ancient ocean called Iapetus (in shades of olive to light green) from the older core of the North American continent (darker colors). The faults that bend and curve are Paleozoic, while the straighter faults were mainly formed during the Mesozoic Era. Today's Connecticut rocks now are all part of North America, of course, but prior to 200 million years ago, Africa and North America (along with the other continents) were all combined in the super-continent of Pangaea.
Q. Do you know of any places around Rhode Island where I could photograph nice-looking minerals in their original rocks?
A. Not personally, but for mineral locations in your area, you could check out Minerals of Rhode Island by C. E. Miller, and Rhode Island Geology for the Non-Geologist by Alonzo Quinn. Both are available for low prices from your state's natural history survey -- posted at http://www.uri.edu/ce/rinhs/books_geology.htm#RIGeology.
Q. Can you tell me about the terrain of Bristol, CT, such as Hoppers-Birge Pond area, Chippens Hill, Hurley Hill. How was the area created, etc.
A. Hello, the Bristol landscape is a result of recent Ice Age glaciers, which eroded bedrock of different hardness along the western border fault of the Mesozoic Hartford basin. When the ice sheet melted, it left huge amounts of glacial till, sand, and gravel, which created much of our landscape. I don't have a summary of the local topography to send you, but I did write about the Hoppers in my book called Great Daytrips to Discover the Geology of Connecticut. It is available from Perry Heights Press at http://www.cttrips.com, and at some local bookstores and libraries.
Q. Hi - I just came across your Conn. Geologist Q&A page - and a question regarding the hazard of breathing in rock dust. I've just been reading about the wondrous effects of volcanic rock dust on trees and gardens; if I start using rock dust to treat the soil, should I take precautions, such as wearing a mask when handling? Should care be taken to keep it tightly sealed when it's being stored?
A. Hello, yes, any kind of rock or mineral dust is bad for your lungs, so either stand upwind when spreading it, or be sure to wear a good dust mask, or do both. The dust settles fairly quickly, so if you close up the bag tightly, there should be no storage hazard (it is not a chemical hazard, more of a physical problem for your lungs). I doubt that occasional use will harm you, but people who are surrounded by rock dust all day are supposed to take more precautions.
By the way, men who have worked in quarries of chrysotile asbestos (the most common type) have about the same rates of lung problems as those who work in quarries and mines where other kinds of minerals and stone are blasted and crushed up. The asbestos problem has been exaggerated, while not enough precautions are taken for rock dust in general.
Volcanic rocks have mineral components that enrich the soil for plants, which is why farms often do better near volcanoes that have been recently active. Best wishes for a productive garden.
Q. I was wondering if you had any resources or ideas on geology summer camps or programs for kids? I have a son who is going into 5th grade who is a fanatic about rocks and gemstones. He is constantly going on the Internet to research rocks. I am trying to find a program for him this summer and haven't been able to. I even emailed Nature's Art to ask if they had anything special for the summer.
A. Hello, geology summer camps for kids do exist (maybe not in Ct), although they may include geology or earth science among several science themes. Find them with Google using a search phrase like "geology summer camp kids" -- there is even one in Iceland, and what a great place for it! Kids (and adults) need more opportunities to experience geology.
Q. I happened upon your "ask a geologist" site while trying to research something and am now writing to you as my best hope for some answers.
I belong to a country club in Kensington named "Shuttle Meadow Country Club." We have recently been trying to determine why our club and the surrounding area is called Shuttle Meadow. I entered Shuttle Meadow into the Google search box and immediately found dozens of sites that refer to something called the "Shuttle Meadow Formation." I have read quite a few of the pieces containing references to this formation and have finally found one that gives a pretty good outline of the extent of this formation. But, we still remain in the dark as to why the formation is called Shuttle Meadow.
Do you have any information about the formation that would prove helpful to me? In particular, when was this formation named the Shuttle Meadow Formation and, if you have any idea, why is it called Shuttle Meadow? I would appreciate any information you can provide me on this topic. Thank you for your assistance.
A. Hello, the Early Jurassic Shuttle Meadow Formation is named after rock exposures near the Shuttle Meadow Reservoir (at least, that is what I heard some time ago). I asked Nancy McHone about the origin of the place name -- she works for the Ct. Geological Survey and also has access to the book "Connecticut Place Names" (1976, Ct. Historical Society). Shuttle Meadow itself is (was) partly in Southington and partly in Berlin. The meadow is now under the Shuttle Meadow Reservoir. The dam for the reservoir dates to 1857, so the name must be older than that. Presumably, it is a colonial name, derived from a resemblance of the meadow's shape to an early weaver's shuttle. The word was also sometimes written as skuttle or shekel. I expect that your club is named after the ancient meadow, not the (more ancient) rock formation.