Geology of Massachusetts
Encyclopedia
The geology of Massachusetts is the result of a process that began over a billion years ago. Massachusetts
currently lies at an edge of a continent, and in the geological past has been the location of many continental collisions and collisions with other microcontinents and volcanic arcs, with their resulting mountain-building events. As a result, the state rock structure is squeezed together. The state has also been the location of a failed attempt at the creation of the Atlantic Ocean
. Recently, multiple Ice Age
s have shaped the modern geology of the state and have created notable landmarks such as Cape Cod
.
s, ancient nuclei of continents and microcontinents begin being found in the geologic record. The ancient continent that was formed, Rodinia
, was a byproduct of these collisions. Worldwide, mountains were being formed in the Grenville orogeny
. Some of the rocks of the Berkshire highlands
are from this era.
Around 750 million years ago, Rodinia began to break up and the Laurentian craton was formed. Two hundred million years later, Gondwana
was formed. Laurentia increased in size because of the addition of Japan
-sized islands. It is possible that the Merrimack, Nashoba, Avalon
, and Meguma
terranes that make up eastern Massachusetts
are remnants of these island arc
s or microcontinents. It is highly likely that these terranes broke off from Gondwana at some point in their history and collided with Laurentia, between 550 and 370 million years ago. These resulting collisions were part of the Taconic orogeny
.The Iapetus Ocean
, separating the two continents began to open up when Rodinia broke apart. The size of the ocean eventually prevented migrations between the two landmasses.
Between 425 and 370 million years ago, the two continents began to collide, forming Pangea. During this time, the Acadian orogeny
, which marked the collision of the two continents, occurred. Around 200 million years ago, Pangea began to break apart. This caused rift valleys to form within the interior of the continent. One of these rift valleys, the Connecticut River Valley is a failed rift of the continent. Basalt dikes present in the underlying rocks of the valleys are the result of volcanism
.
. The Laurentian Terrane is made up of Grenville gneisses of Precambrian
age that formed at the bottom of the continent, continental shelf deposits, and the remains of two volcanic island chains, which constitute the Shelburne Falls and Bronson Hill volcanic chains. The Shelburne Falls chain now lies in the Berkshire foothills, while the Bronson Hill chain lies just east of the present-day Connecticut River Valley. The Taconic Orogeny
, which resulted from the collision of these volcano chains and the continent, helped to thrust, push, and metamorphose the group of Precambrian to early Paleozoic rocks between 485 and 440 million years ago. The terrane is also divided into six structural and stratigraphic divisions.
The divisions are:
. Proof of Avalon being part of Gondwana exists because of trilobite
fossils of the same species that have been found both in Massachusetts
and Africa
. This means that Avalon must have broken away from Gondwana during the end of the Precambrian
, around 550 million years ago. At the very latest, it broke away by the Ordovician
, around 490 million years ago. Fossils of the Meguma terrane also indicate a relation to the northwest Africa margin. The Avalon also originated as a volcanic island chain near the South Pole
, on the fringe of the Gondwanan supercontinent. It is possible that late Precambrian
quartzites of the eastern part of the state were deposited as beach sands on the continental shelf of Gondwana. These deposits were eventually caught in the Avalonian mountain building event, the same deformation which helped to form the Avalonian island chain.
The Nashoba and Merrimack terranes, lying west of the Avalon, probably formed in the ocean near Gondwana
between the Cambrian
and Silurian
time. The basement rocks which form the backbone of the formation dating from the Cambrian
through Silurian
time possibly broke away from Gondwana and headed towards Laurentia
, ahead of the Avalon
terrane. During the Cambrian, the Avalon, along with its companion terranes, began migrating from the South Pole
. These terranes collided with each other over time, as recorded by granite plutons in the rocks.
From west to east:
covered the entire state in thousands of feet of ice. The Wisconsinan glaciation
, thousands of years later, is the most recent glaciation. Estimates of the thickness of this ice have produced results where Mount Wachusett
is covered with slightly more than four hundred feet of ice while Worcester
was covered by anywhere between fifteen hundred and two thousand feet. By 23,000 to 22,000 years ago, New England
was covered in ice. The ice was so thorough in its destruction of the region that the only thing left from the previous glaciation is Nomans Land, to the southwest of Marthas Vineyard.
The ice sheet also contained five glacial lobes which covered the state, the Hudson Valley lobe, the Connecticut Valley-Worcester Plateau lobe, the Narragansett Bay-Buzzards Bay lobe, the Cape Cod Bay lobe, and the South Channel lobe. Where each lobe met, dimples of sediment formed where the meltwater naturally flowed off the glaciers. Terminal moraine
s also formed at the end of these lobes. The lobes that bisected the state helped to form Long Island
, Block Island
, the Elizabeth Islands
, Marthas Vineyard, Cape Cod
, and Nantucket.
between 21,000 and 19,500 years ago. Dating of postglacial materials on Marthas Vineyard indicates that ice melted from it earlier than 15,300 years ago. The Cape Cod Bay lobe was parked outside Boston
for over a thousand years, beginning 16,000 years ago and receded into southwest Maine
by 14,500 years ago. The melting ice released vast amounts of water, resulting in glacial lake
s dotted across the state. The largest, Lake Hitchcock
, stretched from Connecticut
to Vermont
and New Hampshire
. The crust also rebounded at a rate of 4.74 feet per mile, undercutting many of the glacial deposits, especially in the Connecticut River Valley.
Where the moraines met away from the end of the ice also helped deposits. This can be seen in the outer arm of the Cape, originally hills when the ice retreated, they have eroded and shifted over time to help produce the characteristic arm of the Cape.
Massachusetts
The Commonwealth of Massachusetts is a state in the New England region of the northeastern United States of America. It is bordered by Rhode Island and Connecticut to the south, New York to the west, and Vermont and New Hampshire to the north; at its east lies the Atlantic Ocean. As of the 2010...
currently lies at an edge of a continent, and in the geological past has been the location of many continental collisions and collisions with other microcontinents and volcanic arcs, with their resulting mountain-building events. As a result, the state rock structure is squeezed together. The state has also been the location of a failed attempt at the creation of the Atlantic Ocean
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...
. Recently, multiple Ice Age
Ice age
An ice age or, more precisely, glacial age, is a generic geological period of long-term reduction in the temperature of the Earth's surface and atmosphere, resulting in the presence or expansion of continental ice sheets, polar ice sheets and alpine glaciers...
s have shaped the modern geology of the state and have created notable landmarks such as Cape Cod
Cape Cod
Cape Cod, often referred to locally as simply the Cape, is a cape in the easternmost portion of the state of Massachusetts, in the Northeastern United States...
.
Early history
The early history of Massachusetts can be traced to over around 1.2 to 1.1 billion years ago. Ancient rocks made up of cratonCraton
A craton is an old and stable part of the continental lithosphere. Having often survived cycles of merging and rifting of continents, cratons are generally found in the interiors of tectonic plates. They are characteristically composed of ancient crystalline basement rock, which may be covered by...
s, ancient nuclei of continents and microcontinents begin being found in the geologic record. The ancient continent that was formed, Rodinia
Rodinia
In geology, Rodinia is the name of a supercontinent, a continent which contained most or all of Earth's landmass. According to plate tectonic reconstructions, Rodinia existed between 1.1 billion and 750 million years ago, in the Neoproterozoic era...
, was a byproduct of these collisions. Worldwide, mountains were being formed in the Grenville orogeny
Grenville orogeny
The Grenville Orogeny was a long-lived Mesoproterozoic mountain-building event associated with the assembly of the supercontinent Rodinia. Its record is a prominent orogenic belt which spans a significant portion of the North American continent, from Labrador to Mexico, as well as to Scotland...
. Some of the rocks of the Berkshire highlands
The Berkshires
The Berkshires , is a highland geologic region located in the western parts of Massachusetts and Connecticut.Also referred to as the Berkshire Hills, Berkshire Mountains, and Berkshire Plateau, the region enjoys a vibrant tourism industry based on music, arts, and recreation.-Definition:The term...
are from this era.
Around 750 million years ago, Rodinia began to break up and the Laurentian craton was formed. Two hundred million years later, Gondwana
Gondwana
In paleogeography, Gondwana , originally Gondwanaland, was the southernmost of two supercontinents that later became parts of the Pangaea supercontinent. It existed from approximately 510 to 180 million years ago . Gondwana is believed to have sutured between ca. 570 and 510 Mya,...
was formed. Laurentia increased in size because of the addition of Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
-sized islands. It is possible that the Merrimack, Nashoba, Avalon
Avalonia
Avalonia was a microcontinent in the Paleozoic era. Crustal fragments of this former microcontinent underlie south-west Great Britain, and the eastern coast of North America. It is the source of many of the older rocks of Western Europe, Atlantic Canada, and parts of the coastal United States...
, and Meguma
Meguma terrane
The Meguma terrane is a terrane exposed in southern Nova Scotia, that became joined to the present North American landmass as part of the Appalachian orogeny. Composed largely of Cambrian to Ordovician sedimentary deposits, it is joined to the Avalon terrane along the Minas Fault Zone, which runs...
terranes that make up eastern Massachusetts
Massachusetts
The Commonwealth of Massachusetts is a state in the New England region of the northeastern United States of America. It is bordered by Rhode Island and Connecticut to the south, New York to the west, and Vermont and New Hampshire to the north; at its east lies the Atlantic Ocean. As of the 2010...
are remnants of these island arc
Island arc
An island arc is a type of archipelago composed of a chain of volcanoes which alignment is arc-shaped, and which are situated parallel and close to a boundary between two converging tectonic plates....
s or microcontinents. It is highly likely that these terranes broke off from Gondwana at some point in their history and collided with Laurentia, between 550 and 370 million years ago. These resulting collisions were part of the Taconic orogeny
Taconic orogeny
The Taconic orogeny was a mountain building period that ended 440 million years ago and affected most of modern-day New England. A great mountain chain formed from eastern Canada down through what is now the Piedmont of the East coast of the United States...
.The Iapetus Ocean
Iapetus Ocean
The Iapetus Ocean was an ocean that existed in the Neoproterozoic and Paleozoic eras of the geologic timescale . The Iapetus Ocean was situated in the southern hemisphere, between the paleocontinents of Laurentia, Baltica and Avalonia...
, separating the two continents began to open up when Rodinia broke apart. The size of the ocean eventually prevented migrations between the two landmasses.
Between 425 and 370 million years ago, the two continents began to collide, forming Pangea. During this time, the Acadian orogeny
Acadian orogeny
The Taconic, Acadian and Alleghenian orogenies are the three tectonic phases responsible for the formation of the present Appalachian Mountains. The Acadian orogeny is a middle Paleozoic mountain building episode dating back 325-400 million years which should not be regarded as a single event but...
, which marked the collision of the two continents, occurred. Around 200 million years ago, Pangea began to break apart. This caused rift valleys to form within the interior of the continent. One of these rift valleys, the Connecticut River Valley is a failed rift of the continent. Basalt dikes present in the underlying rocks of the valleys are the result of volcanism
Volcanism
Volcanism is the phenomenon connected with volcanoes and volcanic activity. It includes all phenomena resulting from and causing magma within the crust or mantle of a planet to rise through the crust and form volcanic rocks on the surface....
.
Laurentian
The rocks of the Berkshire Hills were once the edge of the ancient continent of LaurentiaLaurentia
Laurentia is a large area of continental craton, which forms the ancient geological core of the North American continent...
. The Laurentian Terrane is made up of Grenville gneisses of Precambrian
Precambrian
The Precambrian is the name which describes the large span of time in Earth's history before the current Phanerozoic Eon, and is a Supereon divided into several eons of the geologic time scale...
age that formed at the bottom of the continent, continental shelf deposits, and the remains of two volcanic island chains, which constitute the Shelburne Falls and Bronson Hill volcanic chains. The Shelburne Falls chain now lies in the Berkshire foothills, while the Bronson Hill chain lies just east of the present-day Connecticut River Valley. The Taconic Orogeny
Taconic orogeny
The Taconic orogeny was a mountain building period that ended 440 million years ago and affected most of modern-day New England. A great mountain chain formed from eastern Canada down through what is now the Piedmont of the East coast of the United States...
, which resulted from the collision of these volcano chains and the continent, helped to thrust, push, and metamorphose the group of Precambrian to early Paleozoic rocks between 485 and 440 million years ago. The terrane is also divided into six structural and stratigraphic divisions.
Divisions
The divisions are:
- Taconic thrust sheet
- Vermont-Stockbridge marble belt
- Berkshire Massif, Hoosac thrust sheet and Row-Hadley belt
- Shelburne Falls Volcanic Belt
- Connecticut River Valley rock intrusion
- Bronson Hill volcanic belt
Gondwanan
The rocks of the Gondwanan terrane are made up of four smaller terranes. These terranes were once part of other continents but have become fused onto the continent over the years. It is generally agreed that two of the terranes, the Meguma and Avalon were once part of GondwanaGondwana
In paleogeography, Gondwana , originally Gondwanaland, was the southernmost of two supercontinents that later became parts of the Pangaea supercontinent. It existed from approximately 510 to 180 million years ago . Gondwana is believed to have sutured between ca. 570 and 510 Mya,...
. Proof of Avalon being part of Gondwana exists because of trilobite
Trilobite
Trilobites are a well-known fossil group of extinct marine arthropods that form the class Trilobita. The first appearance of trilobites in the fossil record defines the base of the Atdabanian stage of the Early Cambrian period , and they flourished throughout the lower Paleozoic era before...
fossils of the same species that have been found both in Massachusetts
Massachusetts
The Commonwealth of Massachusetts is a state in the New England region of the northeastern United States of America. It is bordered by Rhode Island and Connecticut to the south, New York to the west, and Vermont and New Hampshire to the north; at its east lies the Atlantic Ocean. As of the 2010...
and Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
. This means that Avalon must have broken away from Gondwana during the end of the Precambrian
Precambrian
The Precambrian is the name which describes the large span of time in Earth's history before the current Phanerozoic Eon, and is a Supereon divided into several eons of the geologic time scale...
, around 550 million years ago. At the very latest, it broke away by the Ordovician
Ordovician
The Ordovician is a geologic period and system, the second of six of the Paleozoic Era, and covers the time between 488.3±1.7 to 443.7±1.5 million years ago . It follows the Cambrian Period and is followed by the Silurian Period...
, around 490 million years ago. Fossils of the Meguma terrane also indicate a relation to the northwest Africa margin. The Avalon also originated as a volcanic island chain near the South Pole
South Pole
The South Pole, also known as the Geographic South Pole or Terrestrial South Pole, is one of the two points where the Earth's axis of rotation intersects its surface. It is the southernmost point on the surface of the Earth and lies on the opposite side of the Earth from the North Pole...
, on the fringe of the Gondwanan supercontinent. It is possible that late Precambrian
Precambrian
The Precambrian is the name which describes the large span of time in Earth's history before the current Phanerozoic Eon, and is a Supereon divided into several eons of the geologic time scale...
quartzites of the eastern part of the state were deposited as beach sands on the continental shelf of Gondwana. These deposits were eventually caught in the Avalonian mountain building event, the same deformation which helped to form the Avalonian island chain.
The Nashoba and Merrimack terranes, lying west of the Avalon, probably formed in the ocean near Gondwana
Gondwana
In paleogeography, Gondwana , originally Gondwanaland, was the southernmost of two supercontinents that later became parts of the Pangaea supercontinent. It existed from approximately 510 to 180 million years ago . Gondwana is believed to have sutured between ca. 570 and 510 Mya,...
between the Cambrian
Cambrian
The Cambrian is the first geological period of the Paleozoic Era, lasting from Mya ; it is succeeded by the Ordovician. Its subdivisions, and indeed its base, are somewhat in flux. The period was established by Adam Sedgwick, who named it after Cambria, the Latin name for Wales, where Britain's...
and Silurian
Silurian
The Silurian is a geologic period and system that extends from the end of the Ordovician Period, about 443.7 ± 1.5 Mya , to the beginning of the Devonian Period, about 416.0 ± 2.8 Mya . As with other geologic periods, the rock beds that define the period's start and end are well identified, but the...
time. The basement rocks which form the backbone of the formation dating from the Cambrian
Cambrian
The Cambrian is the first geological period of the Paleozoic Era, lasting from Mya ; it is succeeded by the Ordovician. Its subdivisions, and indeed its base, are somewhat in flux. The period was established by Adam Sedgwick, who named it after Cambria, the Latin name for Wales, where Britain's...
through Silurian
Silurian
The Silurian is a geologic period and system that extends from the end of the Ordovician Period, about 443.7 ± 1.5 Mya , to the beginning of the Devonian Period, about 416.0 ± 2.8 Mya . As with other geologic periods, the rock beds that define the period's start and end are well identified, but the...
time possibly broke away from Gondwana and headed towards Laurentia
Laurentia
Laurentia is a large area of continental craton, which forms the ancient geological core of the North American continent...
, ahead of the Avalon
Avalon
Avalon is a legendary island featured in the Arthurian legend. It first appears in Geoffrey of Monmouth's 1136 pseudohistorical account Historia Regum Britanniae as the place where King Arthur's sword Excalibur was forged and later where Arthur was...
terrane. During the Cambrian, the Avalon, along with its companion terranes, began migrating from the South Pole
South Pole
The South Pole, also known as the Geographic South Pole or Terrestrial South Pole, is one of the two points where the Earth's axis of rotation intersects its surface. It is the southernmost point on the surface of the Earth and lies on the opposite side of the Earth from the North Pole...
. These terranes collided with each other over time, as recorded by granite plutons in the rocks.
Divisions
From west to east:
- Merrimack Terrane
- Ware belt
- Gardner belt
- Wachusett Mountain belt
- Southbridge belt
- Nashua belt
- Rockingham belt
- Clinton-Newbury fault zone
- Nashoba Terrane
- Bloody Bluff fault zone
- Avalon Terrane
- Dedham granite
- Boston Basin
- Milford granite (part of the Rhode Island batholith)
- Narragansett Basin
- Fall River batholith
- Nauset fault
- Meguma Terrane
Expansion
Around one million years ago, the continent began experiencing regular ice ages. During the Illinoian period, the Laurentide ice sheetLaurentide ice sheet
The Laurentide Ice Sheet was a massive sheet of ice that covered hundreds of thousands of square miles, including most of Canada and a large portion of the northern United States, multiple times during Quaternary glacial epochs. It last covered most of northern North America between c. 95,000 and...
covered the entire state in thousands of feet of ice. The Wisconsinan glaciation
Wisconsinan glaciation
The Wisconsin Glacial Episode was the most recent major advance of the North American Laurentide ice sheet. Globally, this advance is known as the last glacial period. The Wisconsin glaciation extended from approximately 110,000 to 10,000 years ago, between the Eemian interglacial and the current...
, thousands of years later, is the most recent glaciation. Estimates of the thickness of this ice have produced results where Mount Wachusett
Mount Wachusett
Mount Wachusett is located in the towns of Princeton and Westminster in Worcester County, Massachusetts. It is the highest point in Massachusetts east of the Connecticut River. The mountain is named after a Native American term meaning "near the mountain" or "mountain place". The mountain is a...
is covered with slightly more than four hundred feet of ice while Worcester
Worcester, Massachusetts
Worcester is a city and the county seat of Worcester County, Massachusetts, United States. Named after Worcester, England, as of the 2010 Census the city's population is 181,045, making it the second largest city in New England after Boston....
was covered by anywhere between fifteen hundred and two thousand feet. By 23,000 to 22,000 years ago, New England
New England
New England is a region in the northeastern corner of the United States consisting of the six states of Maine, New Hampshire, Vermont, Massachusetts, Rhode Island, and Connecticut...
was covered in ice. The ice was so thorough in its destruction of the region that the only thing left from the previous glaciation is Nomans Land, to the southwest of Marthas Vineyard.
The ice sheet also contained five glacial lobes which covered the state, the Hudson Valley lobe, the Connecticut Valley-Worcester Plateau lobe, the Narragansett Bay-Buzzards Bay lobe, the Cape Cod Bay lobe, and the South Channel lobe. Where each lobe met, dimples of sediment formed where the meltwater naturally flowed off the glaciers. Terminal moraine
Terminal moraine
A terminal moraine, also called end moraine, is a moraine that forms at the end of the glacier called the snout.Terminal moraines mark the maximum advance of the glacier. An end moraine is at the present boundary of the glacier....
s also formed at the end of these lobes. The lobes that bisected the state helped to form Long Island
Long Island
Long Island is an island located in the southeast part of the U.S. state of New York, just east of Manhattan. Stretching northeast into the Atlantic Ocean, Long Island contains four counties, two of which are boroughs of New York City , and two of which are mainly suburban...
, Block Island
Block Island
Block Island is part of the U.S. state of Rhode Island and is located in the Atlantic Ocean approximately south of the coast of Rhode Island, east of Montauk Point on Long Island, and is separated from the Rhode Island mainland by Block Island Sound. The United States Census Bureau defines Block...
, the Elizabeth Islands
Elizabeth Islands
The Elizabeth Islands are a chain of small islands extending southwest from the southern coast of Cape Cod, Massachusetts in the United States. They are located at the outer edge of Buzzards Bay, north of Martha's Vineyard from which they are separated by Vineyard Sound, and constitute the town of...
, Marthas Vineyard, Cape Cod
Cape Cod
Cape Cod, often referred to locally as simply the Cape, is a cape in the easternmost portion of the state of Massachusetts, in the Northeastern United States...
, and Nantucket.
Retreat
Around 21,000 years ago, the ice began to retreat. Ice began retreating from Long IslandLong Island
Long Island is an island located in the southeast part of the U.S. state of New York, just east of Manhattan. Stretching northeast into the Atlantic Ocean, Long Island contains four counties, two of which are boroughs of New York City , and two of which are mainly suburban...
between 21,000 and 19,500 years ago. Dating of postglacial materials on Marthas Vineyard indicates that ice melted from it earlier than 15,300 years ago. The Cape Cod Bay lobe was parked outside Boston
Boston
Boston is the capital of and largest city in Massachusetts, and is one of the oldest cities in the United States. The largest city in New England, Boston is regarded as the unofficial "Capital of New England" for its economic and cultural impact on the entire New England region. The city proper had...
for over a thousand years, beginning 16,000 years ago and receded into southwest Maine
Maine
Maine is a state in the New England region of the northeastern United States, bordered by the Atlantic Ocean to the east and south, New Hampshire to the west, and the Canadian provinces of Quebec to the northwest and New Brunswick to the northeast. Maine is both the northernmost and easternmost...
by 14,500 years ago. The melting ice released vast amounts of water, resulting in glacial lake
Glacial lake
A glacial lake is a lake with origins in a melted glacier. Near the end of the last glacial period, roughly 10,000 years ago, glaciers began to retreat. A retreating glacier often left behind large deposits of ice in hollows between drumlins or hills. As the ice age ended, these melted to create...
s dotted across the state. The largest, Lake Hitchcock
Lake Hitchcock
Lake Hitchcock was a glacial lake that formed approximately 15,000 years ago in the late Pleistocene epoch. After the Laurentide ice sheet retreated, glacial ice melt accumulated at the terminal moraine and blocked up the Connecticut River, creating the long, narrow lake...
, stretched from Connecticut
Connecticut
Connecticut is a state in the New England region of the northeastern United States. It is bordered by Rhode Island to the east, Massachusetts to the north, and the state of New York to the west and the south .Connecticut is named for the Connecticut River, the major U.S. river that approximately...
to Vermont
Vermont
Vermont is a state in the New England region of the northeastern United States of America. The state ranks 43rd in land area, , and 45th in total area. Its population according to the 2010 census, 630,337, is the second smallest in the country, larger only than Wyoming. It is the only New England...
and New Hampshire
New Hampshire
New Hampshire is a state in the New England region of the northeastern United States of America. The state was named after the southern English county of Hampshire. It is bordered by Massachusetts to the south, Vermont to the west, Maine and the Atlantic Ocean to the east, and the Canadian...
. The crust also rebounded at a rate of 4.74 feet per mile, undercutting many of the glacial deposits, especially in the Connecticut River Valley.
Where the moraines met away from the end of the ice also helped deposits. This can be seen in the outer arm of the Cape, originally hills when the ice retreated, they have eroded and shifted over time to help produce the characteristic arm of the Cape.
