Borrowdale Volcanic Group | |
---|---|
Stratigraphic range: Caradocian (late Ordovician) | |
Type | Group |
Sub-units | Birker Fell Andesite Formation, Whorneyside Tuff Formation, Airy's Bridge Tuff Formation, Lingwell Tuff Formation, Seathwaite Fell Sandstone Formation, Lincomb Tarns Tuff Formation, Esk Pike Formation, Tarn Hows Tuff Formation |
Underlies | Windermere Supergroup |
Overlies | Skiddaw Group |
Thickness | probably up to 6000m |
Lithology | |
Primary | volcanic rocks |
Other | siltstone, sandstone |
Location | |
Region | Cumbria |
Country | England |
Extent | Central Lake District & Cross Fell |
Type section | |
Named for | Borrowdale |
The Borrowdale Volcanic Group is a group of igneous rock formations named after the Borrowdale area of the Lake District, in England. They are Caradocian (late Ordovician) in age (roughly 450 million years old). [1] It is thought that they represent the remains of a volcanic island arc, approximately similar to the island arcs of the west Pacific today. This developed as oceanic crust to the (present) north-west and was forced by crustal movement under a continental land-mass to the present south-east. Such forcing under, as two plates meet, is termed subduction. This land-mass has been named Avalonia by geologists. It is now incorporated into England and Wales and a sliver of North America.
At that time the rocks that now comprise most of Scotland (and part of the northern Irish landmass) were not attached to Avalonia. They were separated by an ocean, called the Iapetus Ocean by geologists. The line of joining, or suture, is approximately under the Solway Firth and Cheviot Hills. In the Lake District, the junction between the early Ordovician series, Skiddaw Slate, and the Borrowdale Volcanic that was forced under it, can be seen on the slopes of Fleetwith Pike.
In the English Lake District, the Borrowdale Volcanic Group is composed of lavas (mainly andesites), tuffs and agglomerates, along with some major igneous intrusions. These rocks of the Borrowdale Volcanic Group give rise to dramatic scenery. The mountainous nature of the area, its high rainfall and the relative impermeability of the rock give rise to a high risk of storm flooding as demonstrated by the 2009 flooding of Cockermouth.
Volcanic activity lasted in the region until, at earliest, the Burrellian period (± 455 MYA). [2]
The upper boundary of the group is an unconformity with the overlying Windermere Supergroup. The lower boundary is an unconformity with the underlying Skiddaw Group. [1]
The outcrop of this sequence on Crinkle Crags (and other surrounding peaks in the Lake District), was chosen as one of the top 100 geosites in the United Kingdom by the Geological Society of London. [3]
The geology of Great Britain is renowned for its diversity. As a result of its eventful geological history, Great Britain shows a rich variety of landscapes across the constituent countries of England, Wales and Scotland. Rocks of almost all geological ages are represented at outcrop, from the Archaean onwards.
Avalonia was a microcontinent in the Paleozoic era. Crustal fragments of this former microcontinent underlie south-west Great Britain, southern Ireland, 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. Avalonia is named for the Avalon Peninsula in Newfoundland.
The Acadian orogeny is a long-lasting mountain building event which began in the Middle Devonian, reaching a climax in the Late Devonian. It was active for approximately 50 million years, beginning roughly around 375 million years ago (Ma), with deformational, plutonic, and metamorphic events extending into the early Mississippian. The Acadian orogeny is the third of the four orogenies that formed the Appalachian Mountains and subsequent basin. The preceding orogenies consisted of the Grenville and Taconic orogenies, which followed a rift/drift stage in the Neoproterozoic. The Acadian orogeny involved the collision of a series of Avalonian continental fragments with the Laurasian continent. Geographically, the Acadian orogeny extended from the Canadian Maritime provinces migrating in a southwesterly direction toward Alabama. However, the northern Appalachian region, from New England northeastward into Gaspé region of Canada, was the most greatly affected region by the collision.
Clough Head is a fell, or hill, in the English Lake District. It marks the northern end of the main ridge of the Helvellyn range and is often walked as part of the ridge walk. The fell stands south of the village of Threlkeld and the A66 road, and it forms the steep eastern side of the tranquil valley of St John's in the Vale.
The Caledonian orogeny was a mountain-building cycle recorded in the northern parts of the British Isles, the Scandinavian Caledonides, Svalbard, eastern Greenland and parts of north-central Europe. The Caledonian orogeny encompasses events that occurred from the Ordovician to Early Devonian, roughly 490–390 million years ago (Ma). It was caused by the closure of the Iapetus Ocean when the Laurentia and Baltica continents and the Avalonia microcontinent collided.
The U.S. state of Georgia is commonly divided into four geologic regions that influence the location of the state's four traditional physiographic regions. The four geologic regions include the Appalachian foreland, Blue Ridge, Piedmont, and Coastal Plain. These four geologic regions commonly share names with and typically overlap the four physiographic regions of the state: the Appalachian Plateau and adjacent Valley and Ridge; the Blue Ridge; the Piedmont and the Coastal Plain.
The geology of England is mainly sedimentary. The youngest rocks are in the south east around London, progressing in age in a north westerly direction. The Tees–Exe line marks the division between younger, softer and low-lying rocks in the south east and the generally older and harder rocks of the north and west which give rise to higher relief in those regions. The geology of England is recognisable in the landscape of its counties, the building materials of its towns and its regional extractive industries.
The Iapetus Suture is one of several major geological faults caused by the collision of several ancient land masses forming a suture. It represents in part the remains of what was once the Iapetus Ocean. Iapetus was the father of Atlas in Greek mythology, making his an appropriate name for what used to be called the 'Proto-Atlantic Ocean'. When the Atlantic Ocean opened, in the Cretaceous period, it took a slightly different line from that of the Iapetus suture, with some originally Laurentian rocks being left behind in north-west Europe and other, Avalonian, rocks remaining as part of Newfoundland.
The Tornquist Sea or Tornquist Ocean was a sea located between the palaeocontinents Avalonia and Baltica about 600 to 450 million years ago. The remains of the sea today form a suture stretching across northern Europe.
The geology of Massachusetts includes numerous units of volcanic, intrusive igneous, metamorphic and sedimentary rocks formed within the last 1.2 billion years. The oldest formations are gneiss rocks in the Berkshires, which were metamorphosed from older rocks during the Proterozoic Grenville orogeny as the proto-North American continent Laurentia collided against proto-South America. Throughout the Paleozoic, overlapping the rapid diversification of multi-cellular life, a series of six island arcs collided with the Laurentian continental margin. Also termed continental terranes, these sections of continental rock typically formed offshore or onshore of the proto-African continent Gondwana and in many cases had experienced volcanic events and faulting before joining the Laurentian continent. These sequential collisions metamorphosed new rocks from sediments, created uplands and faults and resulted in widespread volcanic activity. Simultaneously, the collisions raised the Appalachian Mountains to the height of the current day Himalayas.
For the Skiddaw group of hills, see Skiddaw Group
The Dent Group is a group of Upper Ordovician sedimentary and volcanic rocks in north-west England. It is the lowermost part of the Windermere Supergroup, which was deposited in the foreland basin formed during the collision between Laurentia and Avalonia. It lies unconformably on the Borrowdale Volcanic Group. This unit was previously known as the Coniston Limestone Group or Coniston Limestone Formation and should not be confused with the significantly younger Coniston Group.
The Eycott Volcanic Group is a group of volcanic rock formations of Ordovician age named after the locality of Eycott Hill in the English Lake District. The group overlies the Skiddaw Group and is unconformably overlain by a variety of different Devonian and Carboniferous age rocks.
The Causey Pike Fault or Causey Pike Thrust is a major WSW-ENE trending fault within the Lower Paleozoic rocks of the English Lake District. It is named for Causey Pike, where the fault was first recognised.
Hainan Island, located in the South China Sea off the Chinese coast and separated from mainland China by the Qiongzhou Strait, has a complex geological history that it has experienced multiple stages of metamorphism, volcanic and intrusive activities, tectonic drifting and more. The oldest rocks, the Proterozoic metamorphic basement, are not widely exposed, but mostly found in the western part of the Island.
The geology of Maine is part of the broader geology of New England and eastern North America.
The geology of England's Lake District is dominated by sedimentary and volcanic rocks of mainly Ordovician age underpinned by large granitic intrusions. Younger sedimentary sequences outcrop on the edges of the Lake District area, with Silurian to the south, Carboniferous to the north, east, and west and Permo-Triassic to the west and east. The entire area was covered by a Mesozoic sequence that was eroded off during the Paleogene uplift related to the opening of the North Atlantic. During the Quaternary the area was affected by repeated glaciations, which sculpted the current mountainous landscape.
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The geology of the State of New York is made up of ancient Precambrian crystalline basement rock, forming the Adirondack Mountains and the bedrock of much of the state. These rocks experienced numerous deformations during mountain building events and much of the region was flooded by shallow seas depositing thick sequences of sedimentary rock during the Paleozoic. Fewer rocks have deposited since the Mesozoic as several kilometers of rock have eroded into the continental shelf and Atlantic coastal plain, although volcanic and sedimentary rocks in the Newark Basin are a prominent fossil-bearing feature near New York City from the Mesozoic rifting of the supercontinent Pangea.
The geology of Newfoundland and Labrador includes basement rocks formed as part of the Grenville Province in the west and Labrador and the Avalonian microcontinent in the east. Extensive tectonic changes, metamorphism and volcanic activity have formed the region throughout Earth history.