Mr.
Powers' Earth Science Website
Vergennes
Union High School
Vergennes, Vermont
Vergennes, Vermont
Introduction
The main route that heads north from Vergennes Vermont to Burlington Vermont is route 7 and it generally parallels Lake Champlain as well as the Champlain Thrust Fault that creates some interesting geologic features that are clearly exposed, and in many cases, easily accessible.This website will describe the region we will study and activities that we will perform to carefully analyze the evidence that exists in the local rock record. We will also expand our study of our region beyond the roadcut studies we perform in an effort to better understand the dynamics of the Earth that have shaped our State over time. Students have undoubtedly traveled route 7 from Vergennes to Burlington numerous times in their lives but it is likely that they have never really focused on how the exposed rock along the road changes so dramatically in such a relatively short distance. After this activity the trip to Burlington and back will never be the same.
Geologic History of Western Vermont
Vermont and New Hampshire are a Piedmont that gradually slopes toward the Atlantic Ocean to the east. Vermont is divided into physiographic provinces that run in a generally north-south orientation. The area in which we live and will study is the Champlain Valley and is bordered on the west by Lake Champlain, to the east by the Green Mountains and to the south by the Taconic Mountains. There are a number of important fossil remains in the Valley and ancient reef structures in the northern region are significant Ordovician age indicators of Vermont's early paleoenvironments and latitudinal location.
The tremendous forces of plate tectonics have been important in the last 500 million years in relocating and reshaping the topography of Vermont. The Champlain Valley is geologically bordered on the west by the Adirondack Mountains with Lake Champlain filling a basin between Vermont and upstate New York. There are numerous steep block faults along the Adirondack border and the Champlain Valley is the dropped block of this structure. The eastern side of the Champlain Valley is cut by the Taconic thrust fault that developed during the Taconic orogeny. That shallow angle fault was reactivated during the Acadian orogeny.
The valley has been filled with a glacier during the time of the Laurentide ice sheet, and then by an inland sea as the glacier retreated. Over time the Champlain Sea drained when isostatic rebound allowed the land to rise and subsequently formed Lake Vermont and then Lake Champlain which is now present. Glacial evidence abounds in the region and is another important descriptive topic about Vermont's geologic past that will be addressed in a separate study. During the Ordovician period the area that is now Vermont was covered by a shallow sea that produced many of the shales sandstones and limestones that are the shelf sequence of rocks in the Champlain Valley. The shallow sea that was the proto-Atlantic (Iapetus) ocean began to close by the middle Ordovician with the Taconic orogeny. There are a number of crustal dynamics that occured during this orogeny and the underthrusting crustal slab scraped ocean sediments into subduction zones, created igneous intrusions, and caused up and down shifting along block faults. An offshore island arc that formed eventually merged with the continental mass as the Taconic movement continued west. Shallow angle thrust faults developed and older strata were driven up and over younger rocks that had been previously deposited on top of them. The Champlain Overthrust is dramatically evident at Lone Rock Point in Burlington Vermont.
The Champlain thrust fault runs north and crosses route 7 in a number of locations and the exposed rock cuts provide vivid evidence of the tortuous tectonic forces that have deformed and repositioned the original rock layers of the Champlain Valley. The pressure and temperature associated with the thrust faulting metamorposed sandstone into quartzite and shale into slate.
Thrust faults are a special type of crustal movement that dominate the western geologic structure of Vermont. They are relatively shallow depth faults that produce severe lateral compression. The throw, or distanc that the fault can move is often measured in kilometers due to the rigid nature of the rocks and the shallow nature of the fault (less than 30 degrees).The shallow depth of the fault produces bending and fracturing but little melting. Slightly metamorphosed rocks associated with this type of fault include quartzites, slates, schists and phillites.
Monkton quartzite is prominent in well defined scarps at Mount Philo and Snake Mountain that can be seen from route 7 as one travels north or south. Those structures are one of the slices of the imbricated (overlapping) layers that formed as a result of the westward trending tectonic forces that drove the Champlain Thrust Fault. Thrust faults themselves are inconspicuous in roadcuts but the consequences of the shearing forces often are exhibited in the deformed rock structures and fractures and displaced horizontal beds of the original sedimentary rocks. Those stuctures are the focus of the set of activites this site will present.
The field trip we will take begins in Vergennes Vermont and travels north on Route 7 where we will stop and analyze the rock structures that are visible in various roadcuts along the way.
The map segments below provide a glimpse of the incredible complexity of the bedrock geology of northwestern Vermont. The faultline (black line with points) on the left side of each map represents the Champlain thrust fault that crosses route 7 in several places and is the object of our field study. The left map section would be placed north of the right side map. The general map coordinates for the areas shown is Lat. 44 degrees 20' North, Long. 73 degrees 15' West.
This website was constructed by Mark Powers as a part of the TIG program at Missisippi State University. The following caveat applies.
"The views and opinions expressed on this and following pages are strictly those of the page author or organization. The contents of this page have not been reviewed or approved by Mississippi State University." No photographs include minors.
The main route that heads north from Vergennes Vermont to Burlington Vermont is route 7 and it generally parallels Lake Champlain as well as the Champlain Thrust Fault that creates some interesting geologic features that are clearly exposed, and in many cases, easily accessible.This website will describe the region we will study and activities that we will perform to carefully analyze the evidence that exists in the local rock record. We will also expand our study of our region beyond the roadcut studies we perform in an effort to better understand the dynamics of the Earth that have shaped our State over time. Students have undoubtedly traveled route 7 from Vergennes to Burlington numerous times in their lives but it is likely that they have never really focused on how the exposed rock along the road changes so dramatically in such a relatively short distance. After this activity the trip to Burlington and back will never be the same.
Geologic History of Western Vermont
Vermont and New Hampshire are a Piedmont that gradually slopes toward the Atlantic Ocean to the east. Vermont is divided into physiographic provinces that run in a generally north-south orientation. The area in which we live and will study is the Champlain Valley and is bordered on the west by Lake Champlain, to the east by the Green Mountains and to the south by the Taconic Mountains. There are a number of important fossil remains in the Valley and ancient reef structures in the northern region are significant Ordovician age indicators of Vermont's early paleoenvironments and latitudinal location.
The tremendous forces of plate tectonics have been important in the last 500 million years in relocating and reshaping the topography of Vermont. The Champlain Valley is geologically bordered on the west by the Adirondack Mountains with Lake Champlain filling a basin between Vermont and upstate New York. There are numerous steep block faults along the Adirondack border and the Champlain Valley is the dropped block of this structure. The eastern side of the Champlain Valley is cut by the Taconic thrust fault that developed during the Taconic orogeny. That shallow angle fault was reactivated during the Acadian orogeny.
The valley has been filled with a glacier during the time of the Laurentide ice sheet, and then by an inland sea as the glacier retreated. Over time the Champlain Sea drained when isostatic rebound allowed the land to rise and subsequently formed Lake Vermont and then Lake Champlain which is now present. Glacial evidence abounds in the region and is another important descriptive topic about Vermont's geologic past that will be addressed in a separate study. During the Ordovician period the area that is now Vermont was covered by a shallow sea that produced many of the shales sandstones and limestones that are the shelf sequence of rocks in the Champlain Valley. The shallow sea that was the proto-Atlantic (Iapetus) ocean began to close by the middle Ordovician with the Taconic orogeny. There are a number of crustal dynamics that occured during this orogeny and the underthrusting crustal slab scraped ocean sediments into subduction zones, created igneous intrusions, and caused up and down shifting along block faults. An offshore island arc that formed eventually merged with the continental mass as the Taconic movement continued west. Shallow angle thrust faults developed and older strata were driven up and over younger rocks that had been previously deposited on top of them. The Champlain Overthrust is dramatically evident at Lone Rock Point in Burlington Vermont.
The Champlain thrust fault runs north and crosses route 7 in a number of locations and the exposed rock cuts provide vivid evidence of the tortuous tectonic forces that have deformed and repositioned the original rock layers of the Champlain Valley. The pressure and temperature associated with the thrust faulting metamorposed sandstone into quartzite and shale into slate.
Thrust faults are a special type of crustal movement that dominate the western geologic structure of Vermont. They are relatively shallow depth faults that produce severe lateral compression. The throw, or distanc that the fault can move is often measured in kilometers due to the rigid nature of the rocks and the shallow nature of the fault (less than 30 degrees).The shallow depth of the fault produces bending and fracturing but little melting. Slightly metamorphosed rocks associated with this type of fault include quartzites, slates, schists and phillites.
Monkton quartzite is prominent in well defined scarps at Mount Philo and Snake Mountain that can be seen from route 7 as one travels north or south. Those structures are one of the slices of the imbricated (overlapping) layers that formed as a result of the westward trending tectonic forces that drove the Champlain Thrust Fault. Thrust faults themselves are inconspicuous in roadcuts but the consequences of the shearing forces often are exhibited in the deformed rock structures and fractures and displaced horizontal beds of the original sedimentary rocks. Those stuctures are the focus of the set of activites this site will present.
The field trip we will take begins in Vergennes Vermont and travels north on Route 7 where we will stop and analyze the rock structures that are visible in various roadcuts along the way.
The map segments below provide a glimpse of the incredible complexity of the bedrock geology of northwestern Vermont. The faultline (black line with points) on the left side of each map represents the Champlain thrust fault that crosses route 7 in several places and is the object of our field study. The left map section would be placed north of the right side map. The general map coordinates for the areas shown is Lat. 44 degrees 20' North, Long. 73 degrees 15' West.
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This website was constructed by Mark Powers as a part of the TIG program at Missisippi State University. The following caveat applies.
"The views and opinions expressed on this and following pages are strictly those of the page author or organization. The contents of this page have not been reviewed or approved by Mississippi State University." No photographs include minors.