- Barrier Beach
- Basalt Erratics
- Basalt Flows
- Columnar Basalt
- Connecticut River Valley
- Differential Weathering
- Drainage Basin
- Drainage Patterns
- Glacial Erratic
- Glacial Groove / Striations
- Glacial Lake Hitchcock
- Glacial Till
- Hartford Basin
- Lava Pillows
- Meander
- Metacomet Ridge
- Moraine
- Oxbow Lake
- Potholes
- Rift Valley
- Spit
- Taconics
- Talus Slope or Scree
- Trap rock Ridge
- Volcanic Lava Dome
- Waterbury Dome
Barrier Beach: A barrier island is an island of sand and pebbles just off the main shore that runs parallel to it and protects it from the turbulent ocean waters. New Jersey has clear examples of barrier island. Check out this satellite image of the Point Pleasant, Seaside Heights, etc, barrier island.
A barrier beach is roughly the same thing but one end is connected to mainland and it also must not become submerged at high tide.
Where in CT? Bluff Point Spit is also a mile long barrier beach protecting the salt marsh behind it from the full storm surges of the Atlantic. Swimming or wading in the calmer salt marsh is often quite relaxing.
Basalt Erratic --erratics are rocks moved by glaciers. Basalt tends to break up easily when transported by water or ice so the occurrence of a basalt erratic is unlikely.
I am not 100% convinced the picture on the left is a basalt erratic. It fits the description (color?, size, shape) and was found in the area the CT DEP said it would be (location) so there is a good chance this is in fact a basalt erratic. If anyone knows with certainty one way or the other feel free to contact me. I'll try to head back this summer when the leaves are gone. This is from the CT DEP on Southford Falls:
"Continuing on around to the east side of the park, the trail passes through a valley. Along the trail about half way to the pond, you may start to see dark brown potato-shaped stones in the trail. Some are as large as a foot across. These are pieces of basalt moved south by the glacier from somewhere north of I-84 where there are the remains of small basalt flows from about 200 million years ago. Basalt tends to break up easily when transported by water or ice, so it is unusual to see basalt erratics, as rocks moved by glaciers are called. Basalt is dark gray, but weathers to a rusty brown color because of its iron content."
Where in CT? At Southford Falls half way between the Fire Tower and the back end of the Pond.
Columnar Basalt: During the cooling of a thick lava flow, contractional joints or fractures form. If a flow cools relatively rapidly, significant contraction forces build up. While a flow can shrink in the vertical dimension without fracturing, it cannot easily accommodate shrinking in the horizontal direction unless cracks form; the extensive fracture network that develops results in the formation of columns. The topology of the lateral shapes of these columns can broadly be classed as a random cellular network. These structures are often erroneously described as being predominantly hexagonal. In reality, the mean number of sides of all the columns in such a structure is indeed six (by geometrical definition), but polygons with three to twelve or more sides can be observed[5]. Note that the size of the columns depends loosely on the rate of cooling; very rapid cooling may result in very small (<1 cm diameter) columns, while slow cooling is more likely to produce large columns.
Where in CT? They are certainly not the nicest columnar basalt around. Look at the examples from wikipedia such as Devil's Tower or Ireland's. These can look remarkable but the ones in Connecticut are still worth looking at. You can find them in the trap rock ridges of the CT river valley. Giufridda Park, On the way to Mount Higby, from I691 and so on.
Drainage Basin: A drainage basin is an extent of land where water from rain or snow melt drains downhill into a body of water, such as a river, lake, reservoir, estuary, wetland, sea or ocean.
The drainage basin includes both the streams and rivers that convey the water as well as the land surfaces from which water drains into those channels, and is separated from adjacent basins by a drainage divide. The drainage basin acts like a funnel, collecting all the water within the area covered by the basin and channeling it into a waterway. Each drainage basin is separated topographically from adjacent basins by a geographical barrier such as a ridge, hill or mountain, which is known as a water divide.
Drainage Basin's are often referred to as Watersheds. The Connecticut River is a very significant New England drainage basin .
Drainage Patterns-- four basic drainage types are delineated on the left. In addition to these parallel, centripetal and deranged patterns also exist. Rectangular usually form in areas of faulting. Streams follow the path of least resistance and tributaries mark sharp turns when entering the main stream. Radial occur at a highly elevated point, such as on a volcano. Water flows down it on all sides. Trellis drainage occurs in areas of folded topography (e.g. synclines). Dendritic is the most common and occurs when regions are underlain by homogenous material. AKA the sub-surface geology weathers in a similar fashion so there is no apparent control over the path tributaries take. Look at the map of CT rivers and determine what type of drainage pattern Connecticut has.
Click the map for a larger picture. Connecticut has areas where tributaries connect with larger rivers at virtually right angles and many of them generally head towards the coast (parallel to an extent) and some head more E-W then N-S but for the most part, Connecticut has a dendritic drainage pattern.
Glacial Grooves / Striations -- place the mouse over the image to see a rollover.
Glacial grooves or striations are scratches or gouges cut into bedrock by processes of glacial abrasion. As glaciers advance they pick up rocks and other debris which are constantly churning inside the advancing ice sheet (entrainment and/or plucking). Glacial till is what we see scattered all around New England and was once churning about inside a thick ice sheet which was so thick and heavy the ice experienced a "plastic flow". Plastic flow occurs when ice sheets have a depth greater than 50 meters. it is thought that the last ice age in Connecticut featured ice sheets a mile thick in some places! Till unsorted glacial sediment and is left around various types of glacial moraines and results from glacial meltouts.
The griding or abrasive motion of churning and moving sedminets inside glaciers carve out grooves or scratches in rock surfaces they move over. lkm
Where in CT? A few spots in CT have glacial striations and grooves. I took the photograph on the left on the Mattabasset trail on top of Mount Higby just off of where the I691 expressway ends. This area features one of the most exciting
Lava Pillows are a lava structure typically formed when lava emerges from an underwater volcanic vent or subglacial volcano or a lava flow enters the ocean. However, pillow lava can also form when lava is erupted beneath thick glacial ice. The viscous lava gains a solid crust on contact with the water, and this crust cracks and oozes additional large blobs or "pillows" as more lava emerges from the advancing flow. Since water covers the majority of Earth's surface and most volcanoes are situated near or under bodies of water, pillow lava is very common.
Remember that Lava starts as magma from within the Earth and once it breaches the surface it acquires its new name (Lava).
Where in CT? These pillows are visible in Connecticut behind the Target next to the Meriden Mall which is a conservation area and also features a Talus Slope. I have a full page devoted to these lava pillows.
Meander -- a loop like bend in the course of a river or stream. A meander is formed when the moving water in a river erodes the outer banks and widens its valley. A stream of any volume may assume a meandering course, alternatively eroding sediments from the outside of a bend and depositing them on the inside. The result is a snaking pattern as the stream meanders back and forth across its down-valley axis.
Here on the left is a meander in the Connecticut River. These are common in numerous rivers and streams throughout Connecticut. This is the beginning of the formation of an oxbow lake.
Oxbow Lake -- that is not an oxbow lake but it is one of the closest examples I could find in CT and it occurs on the Farmington River just before it dumps into the Connecticut River. The Connecticut River actually does have an oxbow in Northhampton Massachusetts.
Notice around the bend where I put the red E. That appears to be widening a bit due to erosion and the fact that water at that outer end is moving faster than at the opposite side of the river. It a significant amount of further erosion occurred over time eventually it could erode so much that the bend reaches the next river. Thus we would be left with a small u shaped cutoff lake that has the shape of an "oxbow". In this case the trees and the fact that erosion exists on only one said makes it unlikely to me that an oxbow lake could form anytime soon. But using the Google Earth ruler there is only 1/10 of a mile in the way of an oxbow lake forming.
Usually significant amounts of erosion occur during flooding events and this is the idea condition for the formation of an Oxbow lake. Erosion is working from two ends to cut off the river:
POTHOLE FORMATION: When you have rapidly moving water small trapped rocks and pebbles in eddy currents can spin because of the water pressure. As the rocks and particles spin they burrow a hole into the rock below (like a screw or drill in a sense). Once those particles grind into nothing others replace them and continue the process
Pothole: depression formed in a stream channel by the abrasive action of the water's sediment load.
Where in CT? Potholes are found allover, wherever there are or were turbulent streams. They can be seen at Kent Falls, around Buttermilk Falls, the Prospect Water Control Falls and numerous other rivers throughout Connecticut. The best Potholes probably occur in Devil's Hopyard State Park in East Haddam, however. I have a whole page dedicated to this area.
Principal Peaks in CT -- All CT's principal peaks occur in the Northwestern Hills and are part of the Taconics Mountain Range. They as are visible in the NorthWest here and once stood at 20,000 feet. Bear Mountain offers the highest elevation gain for probably any hike strictly in Connecticut (ca. 1500ft).
Some Principle Peaks around CT: (once around 20,000 ft)
- Bear Mountain 2316'—highest mt. : in CT.
- Mount Frissell 2453'– highest point in CT; slope of Frissell.
- Round Mountain 2296' —on the Frissell trail
- Mount Brace (not in CT) 2311' ---on the Frissell trail.
- South Brace (not in CT) 2304' on Frissell trail.
- Mount Gridley 2,192 ' South of Bear Mountain
Click the image on the left for a zoomed in contour image of Bear Mountain and Mount Frissell. If you look close enough at the contours it is easy to see that Bear Mountain is the highest summit in CT but that the slope up to Mount Frissell is actually higher at the CT border than Bear Mt. summit. Note the contour scale is 40 feet per line on Google Maps.
Spit --a long ridge of sand that is a deposition landform found off coasts. At one end, spits connect to land, while at the far end they exist in open water. A spit is a type of bar or beach that develops where a re-entrant occurs, such as at cove's headlands, by the process of long shore drift.
From CT DEP: "Sand at Bluff Point generally moves from east to west. The beach would probably extend over to the airport area if the Poquonock River didn't move the sand out into the Sound. At one time the beach did extend to Bushy Point, but the 1938 hurricane breached the beach, separating it from what is now Bushy Point Island, at least at high tide. The beach is now a spit. When it was connected to the island it was a tombolo. Since beaches are constantly changing, due to wind and waves, the beach may at some time again be connected to the island. Or another storm could breach the spit of sand and break it into more islands."
Where in Connecticut? Bluff Point State Park. This mile long barrier beach actually connects to a smaller island at its tip. I walked out to it on a sand bar. The water was about 3' deep at max and I walked 50 yards or so. In this regard it is pretty close to a tombolo, even at low tide. The island was fun to explore!
The Taconics are a subset of the Appalachian Range and consist of a narrow range of mountains that straddle the borders of Connecticut, New York, Vermont and Massachusetts. These are the Principal peaks of CT as are visible in the NorthWest here.
- Location: Northwestern Section of Connecticut.
- Age: Some of the rock in this area is almost 1.4 byo from Proto-North America and the taconics formed about 415 million years ago during the Taconic Oregeny.
- Mountain Type: Thrust fault, collision of continent with volcanic island arc.
- Rock Type: primarily Gneiss (pronounced nice) which is a metamorphic rock.
Taconic Oregeny—this is the mountain building event that occurred during the early formation of Pangea long after super-continent Rodinia disassembled. 445 mya Europe and North America drifted towards each other. There were volcanic island arcs off the coast (similar to Japan) which were pushed into the mainland (ca. 435 mya) which caused the formation of the Taconic mountains. At this point they reached their terminal peak of probably around 20,000 feet. Now they are just bigger than 1/10th of their original terminal peak due to weathering and erosion. Note that a continent-continent collision will produce higher mountains than a continent-volcanic island arc collision.
WHERE in CT? Northwest Portion of Connecticut identifiable here. You can also take a nice Taconic Drive through New York on the border of Connecticut (follow Country Route 63 and/or Route 22 and then stop at the Taconic State Park and see Bash Bish Falls in Mass!
Talus or Scree Slopes Scree, also called talus, is a term given to an accumulation of broken rock fragments at the base of crags, mountain cliffs, or valley shoulders. Landforms associated with these materials are sometimes called scree slopes or talus piles. These deposits typically have a concave upwards form, while the maximum inclination of such deposits corresponds to the angle of repose of the mean debris size.
They appear to form due to frost wedging and are common in connecticut on the slopes of its trap rock ridges. Talus slopes are sometimes difficult to walk up depending on the size of the debris. If its small then "two steps up, one step back" might apply due to sliding.
Where in CT? Around the Merimere Reservoir in Hubbard Park, Behind Target in Meriden, On the Slope of Chauncey Peak in Giuffrida Park and other places throughout CT.
Trap Rock Ridge --I am referring to the basaltic trap rock ridges in the Connecticut River valley in the Hartford Basin and along the Metacomet Ridge. The Metacomet ridge consists of faulted and lifted basalt flows; aka igneous rock that was once molten lava but has cooled and solidified.
From Wiki: "Trap rock is a form of plutonic igneous rock that tends to form polygonal vertical fractures, most typically hexagonal, but also four to eight sided. The fracture pattern forms when magma of suitable chemical composition (typically basaltic) intrudes as a sill or extrudes as a thick lava flow, and slowly cools. Because of the regular vertical fracture planes plus frequent horizontal fractures, trap rock tends to appear in orderly structures resembling piles of blocks, sometimes reminiscent of stairs and inspiring the term "trap", which derives from a Scandinavian word meaning "steps" or "stairs"." So it is very similar to the columnar basalt discussed above.
Just realize these are volcanic extrusions of igneous rock (dried up lava) that tells how how active Connecticut was in its past. According to Greg Mchone, "The traprock ridges of the Hartford Basin were formed by three, huge volcanic flows known to have occurred in the valley about 200 million years ago. They are not very high, perhaps a few hundred feet, but their rugged western faces and tall cliffs of eroded, columnar basalt give these central ridges their appearance." (Great Day Trips, TDTGOC, p. 97) The Metacomet ridge consists of faulted and lifted diabese (basalt).
When you walk over this stone stop and pick a piece up and realize that you are holding 200 million year old lava; the result of the breakup of Pangea which led to a rift valley forming in Connecticut with three huge lava flows.
Where in CT? You can find them very well pronounced in the Meriden Area. The road cuts on I691 are basaltic trap rock and so is Mount Higby, Castle Craig, etc. Mount Higby is right at the end of the I691 expressway (there is a parking lot) and a blue trail leading up into the woods provides visitors with arguably, the best cliff walking in Connecticut. We also have Talcott Mountain, Sleeping Giant, West Rock Ridge State Park, East Rock, Stratton Brook State Park and the Coginchaug River which cascades over columnar basalt at Wadsworth Falls State Park.
Volcanic Lava Domes in Connecticut
I bought "Roadside Geology of Connecticut and Road Island" by James W. Skehan (a great book!) and found out much to my surprise and astonishment, my own home town lies on the heart of an ancient volcanic lava dome--and there are several throughout CT. Who would have thought? I lived here my entire life not knowing I was sitting on the remnants of an ancient volcano.
This volcano existed 480 million years ago as the Shelburne falls volcanic island arc collided with Laurentia. This is similar to what is occurring in Japan today (Island Arc to Continent collision). The south-flowing Naugatuck river has cut deep through the cambrian aged Waterbury Gneiss. So this volcano existed long before Pangea broke up or had even formed. The Iapetus ocean was still extant and Gondowana and Laurentia had separated (formerly the supercontnent Rodinia) and Pangea was just starting to come together. Some more information about the Waterbury dome with many thank to Skehan:
- 11 miles at the surface though its truncated by faults on the E and W. Width probably increases with depth.
- Eastern margin was cut by Seymour Fault and the Western area is bound by the Pomperaug fault.
- Overlying the WD is a narrow band of a felsic granular basal member from the Taine Mountain Formation from the Ordovician period which is interleaved with silvery schists from the Collinsville formation.
- Circling the WD is Straights Schist which was deposited over the top of the volcanic domes in Devonian time.
- The dominant metamorphism in the WD occurred during the Taconic orogeny (ca. 460mya).
- Ordovician strata around the core delineate Devonian metamorphisism from the Acadian mountain building event.
A sense of scale of the Waterbury Dome can be seen here (a free geo-map software I have found). You are looking for the feature labeled Wtby Dome in the image on the left.
Where in CT? There is the Bristol Dome, Seymore Dome, and several others that formed hundreds of millions of years ago but very spectacular outcrops of Waterbury Gneiss are visible in the Waterbury Dome. The Waterbury Dome can be seen in the rock outcrops on I84 across from the mall where Holy Land is located between exits 23 and 22. This rock is called Waterbury Gneiss (pronounced nice) and it is metamorphic (forms under immense heat and pressure--in this case at least significantly the Taconic orogeny or mountain building event). As this is my hometown and I pass by it every day I will put a very good picture of it up soon. In reality, all you will see is a picture of a mound of Gneiss, a very abundant metamorphic rock throughout our state but considering its history, I find it fascinating.