: ''This article describes the

geology Geology () is a branch of natural science concerned with Earth and other astronomical objects, the features or rocks of which it is composed, and the processes by which they change over time. Modern geology significantly overlaps all other Ea ...

of the historic county of Northumberland. It does not include that southeastern part of the historic county which has since 1974 formed a part of the metropolitan county of

Tyne and Wear Tyne and Wear () is a metropolitan county in North East England, situated around the mouths of the rivers Tyne and Wear. It was created in 1974, by the Local Government Act 1972, along with five metropolitan boroughs of Gateshead, Newc ...

'' The geology of Northumberland in northeast

England England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe b ...

includes a mix of

sedimentary Sedimentary rocks are types of rock that are formed by the accumulation or deposition of mineral or organic particles at Earth's surface, followed by cementation. Sedimentation is the collective name for processes that cause these particles ...

, intrusive and extrusive igneous rocks from the Palaeozoic and Cenozoic eras. Devonian age volcanic rocks and a

granite Granite () is a coarse-grained ( phaneritic) intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly cools and solidifies under ...

pluton form the Cheviot massif. The geology of the rest of the county is characterised largely by a thick sequence of sedimentary rocks of Carboniferous age. These are intruded by both

Permian The Permian ( ) is a geologic period and System (stratigraphy), stratigraphic system which spans 47 million years from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.9 Mya. It is the last ...

and

Palaeogene The Paleogene ( ; also spelled Palaeogene or Palæogene; informally Lower Tertiary or Early Tertiary) is a geologic period and system that spans 43 million years from the end of the Cretaceous Period million years ago ( Mya) to the beginning o ...

dykes and sills and the whole is overlain by unconsolidated sediments from the last ice age and the post-glacial period. The

Whin Sill The Whin Sill or Great Whin Sill is a tabular layer of the igneous rock dolerite in County Durham, Northumberland and Cumbria in the northeast of England. It lies partly in the North Pennines Area of Outstanding Natural Beauty and partly in Nort ...

makes a significant impact on Northumberland's character and the former working of the

Northumberland Coalfield The Northumberland Coalfield is a coalfield in north-east England. It is continuous with the Durham Coalfield to its south. It extends from Shilbottle in the north to the boundary with County Durham along the River Tyne in the south, beyond which ...

significantly influenced the development of the county's economy. The county's geology contributes to a series of significant landscape features around which the

Northumberland National Park Northumberland National Park is the northernmost national park in England. It covers an area of more than between the Scottish border in the north to just south of Hadrian's Wall, and it is one of least visited of the National Parks. The park ...

was designated.

Silurian

Rocks of the Gala Group outcrop near Berwick.

Greywacke Greywacke or graywacke (German ''grauwacke'', signifying a grey, earthy rock) is a variety of sandstone generally characterized by its hardness, dark color, and poorly sorted angular grains of quartz, feldspar, and small rock fragments or lit ...

s originating during the Wenlock epoch of the Silurian Period are assigned to the Riccarton Group and occupy an area either side of the border to the north of

Byrness Byrness is a village within Rochester civil parish in Northumberland, England. It is approximately north-west of Newcastle upon Tyne on the A68, and is the last village in England before the A68 climbs the Cheviot Hills to cross Carter Bar i ...

Devonian

Old Red Sandstone

The late Devonian Stratheden Group is characterised by sandstones with subordinate siltstones and mudstones. A small area of these rocks straddles the border to the southwest of

The Cheviot The Cheviot () is an extinct volcano and the highest summit in the Cheviot Hills and in the county of Northumberland. Located in the extreme north of England, it is a walk from the Scottish border and, with a height of above sea-level, is lo ...

Igneous rocks

Rocks assigned to the Cheviot Volcanic Formation, itself within the

Reston Group The Reston Group is a Silurian to Devonian lithostratigraphic group (a sequence of rock strata) in the Southern Uplands terrane of southern Scotland Scotland (, ) is a Countries of the United Kingdom, country that is part of the Unit ...

, straddle the border with Scotland. This thick pile (over 1000m) of

andesitic Andesite () is a volcanic rock of intermediate composition. In a general sense, it is the intermediate type between silica-poor basalt and silica-rich rhyolite. It is fine-grained (aphanitic) to porphyritic in texture, and is composed predomin ...

lava Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a moon onto its surface. Lava may be erupted at a volcano or through a fracture in the crust, on land or un ...

s was erupted during the early Devonian. The sequence includes rhyolites, agglomerates and

tuff Tuff is a type of rock made of volcanic ash ejected from a vent during a volcanic eruption. Following ejection and deposition, the ash is lithified into a solid rock. Rock that contains greater than 75% ash is considered tuff, while rock ...

. The Cheviot Pluton is a mass of Devonian

Carboniferous

Yoredale Group

The

Inverclyde Group The Inverclyde Group is a Carboniferous lithostratigraphic group (a sequence of rock strata) in southern Scotland and northernmost England. The name is derived from Inverclyde. The rocks of the Inverclyde Group have also previously been referre ...

extends from to the Scottish border near

. Rocks of the

Border Group The Border Group is a Carboniferous lithostratigraphic group (a sequence of rock strata) in southern Scotland and northernmost England. The name is derived from the Scottish Borders The Scottish Borders ( sco, the Mairches, 'the Marche ...

extend in a broken and faulted belt south from Berwick towards Alnwick then southwest via Rothbury then onward to the county boundary west of Kielder Water. Within the Border Group the Fell Sandstone Formation reaches up to 370m thickness and is locally prominent around Rothbury Forest where it also forms the

Simonside Hills The Simonside Hills are a hill range in Northumberland, England near the town of Rothbury. Most of the hills are around high and are popular spots for hikers in the area. The highest point is Tosson Hill at . There are several single pitch roc ...

which reach a height of 440m at Tosson Hill. The Yoredale Group comprises, in stratigraphic order i.e. lowermost/oldest first, the Tyne Limestone Formation, Alston Formation and Stainmore Formation. This succession is formed from mudstones, siltstones, sandstones and limestone. The Tyne Limestone forms a narrow and faulted belt of country south and southeast from

Berwick-upon-Tweed Berwick-upon-Tweed (), sometimes known as Berwick-on-Tweed or simply Berwick, is a town and civil parish in Northumberland, England, south of the Anglo-Scottish border, and the northernmost town in England. The 2011 United Kingdom census reco ...

to Alnwick. It also occupies a large area around Otterburn, Bellingham and Kielder Reservoir extending west to the Cumbrian border. The overlying Alston Formation extends south from the Scottish border along the coastal strip before turning inland through Alnwick towards Greenhead. It plays host to the intrusive

. Besides a few inliers further north, the main outcrop of the Stainmore Formation stretches from the coast south of

Craster Craster is a small fishing village on the Northumberland coast of England, from Alnwick. The next village to the north is Embleton. It has a small harbour and offers a view northwards along the rocky shore to the ruins of Dunstanburgh Cast ...

towards Hexham and west along the valley of the

South Tyne South is one of the cardinal directions or compass points. The direction is the opposite of north and is perpendicular to both east and west. Etymology The word ''south'' comes from Old English ''sūþ'', from earlier Proto-Germanic ''*sunþaz ...

Coal Measures

The sandstones, siltstones, mudstones and

coal Coal is a combustible black or brownish-black sedimentary rock, formed as rock strata called coal seams. Coal is mostly carbon with variable amounts of other elements, chiefly hydrogen, sulfur, oxygen, and nitrogen. Coal is formed when ...

s of the

Pennine Coal Measures Group The Pennine Coal Measures Group is a lithostratigraphical term referring to the coal-bearing succession of rock strata which occur in the United Kingdom within the Westphalian Stage of the Carboniferous Period. In formal use, the term replaces ...

overlie the Stainmore Formation and, from a line roughly between

Amble Amble is a town on the North Sea coast of Northumberland, England, at the mouth of the River Coquet; Coquet Island is visible from its beaches and harbour. In 2011, it had a population of 6,025. Etymology There are two suggested origins of ...

and Derwent Reservoir via

Morpeth Morpeth may refer to: *Morpeth, New South Wales, Australia ** Electoral district of Morpeth, a former electoral district of the Legislative Assembly in New South Wales * Morpeth, Ontario, Canada * Morpeth, Northumberland, England, UK ** Morpeth (UK ...

Ponteland Ponteland ( ) is a large village and civil parish in Northumberland, England, north of Newcastle upon Tyne. The name means "island in the Pont", after the River Pont which flows from west to east and joins the River Blyth further downstream, be ...

and

Stocksfield Stocksfield is a small, yet sprawling commuter village situated close to the River Tyne, about west of Newcastle upon Tyne in the southern part of Northumberland, England. There are several smaller communities within the parish of Stocksfie ...

, extend eastwards to the coast with a gentle regional dip towards the North Sea basin. The upper Coal Measures are absent from Northumberland. Further small

outliers In statistics, an outlier is a data point that differs significantly from other observations. An outlier may be due to a variability in the measurement, an indication of novel data, or it may be the result of experimental error; the latter are ...

of the lower Coal Measures extend westwards to the Cumbrian border southwest of

Haltwhistle Haltwhistle is a market town and civil parish in Northumberland, England, east of Brampton. It had a population of 3,811 at the 2011 Census. Stone-built houses are a feature of Haltwhistle. It is one of two settlements in Great Britain which c ...

. The

is contiguous with the

Durham Coalfield The Durham Coalfield is a coalfield in north-east England. It is continuous with the Northumberland Coalfield to its north. It extends from Bishop Auckland in the south to the boundary with the county of Northumberland along the River Tyne in the ...

to its south. the Tyne valley outliers gave rise to the very minor Stublick,

Plenmeller Plenmeller is a village and former civil parish, now in the parish of Plenmeller with Whitfield, in Northumberland, England about a mile (1½ km) southeast of Haltwhistle. In 1951 the parish had a population of 107. Governance Plenme ...

and Midgeholme

coalfield A coalfield is an area of certain uniform characteristics where coal is mined. The criteria for determining the approximate boundary of a coalfield are geographical and cultural, in addition to geological. A coalfield often groups the seams of ...

Permian

The

tholeiitic The tholeiitic magma series is one of two main magma series in subalkaline igneous rocks, the other being the calc-alkaline series. A magma series is a chemically distinct range of magma compositions that describes the evolution of a mafic magma ...

basalt Basalt (; ) is an aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the surface of a rocky planet or moon. More than 90 ...

of the

was emplaced during early Permian times. As much as 215 cubic kilometres of quartz-dolerite may have been emplaced within lower Carboniferous bedrock in a sheet which extends to more than 4500 square kilometres of Northumberland and county Durham and which is typically 30m thick. A series of dyke sub-swarms is associated with the sill. Those within Northumberland are referred to as the Holy Island, High Green and St. Oswald's subswarms. The sill provides for characterful topography at Dunstanburgh, Bamburgh, Lindisfarne and neighbouring districts including the

Farne Islands The Farne Islands are a group of islands off the coast of Northumberland, England. The group has between 15 and 20 islands depending on the level of the tide.

, offering several good sites for the construction of castles. Further south it provides the extended north-facing scarp on which the Roman emperor Hadrian had his eponymous wall built.

Palaeogene

Numerous dykes of

age cut the sedimentary rocks of the county. The most significant is the Acklington Dyke which running roughly east-southeastwards from the vicinity of the Scottish town of

Hawick Hawick ( ; sco, Haaick; gd, Hamhaig) is a town in the Scottish Borders council area and historic county of Roxburghshire in the east Southern Uplands of Scotland. It is south-west of Jedburgh and south-south-east of Selkirk. It is one ...

parallels the course of the Coquet, running just north of

Rothbury Rothbury is a market town and civil parish in Northumberland, England, on the River Coquet. It is northwest of Morpeth and of Newcastle upon Tyne. At the 2001 Census, it had a population of 2,107. Rothbury emerged as an important town be ...

and through the village of

Acklington Acklington is a small village in Northumberland, England. It is situated to the south-west of Amble, inland from the North Sea coast. It is served by Acklington railway station. The name is Anglo-Saxon Old English 'farmstead of Eadlac's people'. ...

towards the coast. The dyke occasionally achieves a width of 30m. A Blyth subswarm and a Sunderland subswarm of broadly parallel dykes are recognised as likely emanating from the same source, the

Mull Mull may refer to: Places *Isle of Mull, a Scottish island in the Inner Hebrides ** Sound of Mull, between the Isle of Mull and the rest of Scotland * Mount Mull, Antarctica *Mull Hill, Isle of Man * Mull, Arkansas, a place along Arkansas Highway ...

igneous centre in the west of Scotland.

Structure

Northumberland sits above the

Iapetus Suture The Iapetus Suture is one of several major Fault (geology), geological faults caused by the collision of several ancient land masses forming a suture (geology), suture. It represents in part the remains of what was once the Iapetus Ocean. Iapet ...

, the line along which the former Iapetus Ocean closed during the Palaeozoic, thereby causing the

Caledonian Orogeny The Caledonian orogeny was a mountain-building era recorded in the northern parts of the British Isles, the Scandinavian Mountains, Svalbard, eastern Greenland and parts of north-central Europe. The Caledonian orogeny encompasses events that ...

. During Carboniferous times, the Northumberland basin occupied the ground between the Cheviot block to the north and the Alston Block to the south.

Quaternary

Glacial legacy

The larger part of the county is mantled by glacial

till image:Geschiebemergel.JPG, Closeup of glacial till. Note that the larger grains (pebbles and gravel) in the till are completely surrounded by the matrix of finer material (silt and sand), and this characteristic, known as ''matrix support'', is d ...

from the last i.e. Devensian glaciation. There are also a number of areas of glacio-fluvial sands and gravels representing glacially derived material re-worked by rivers. All of this material, till and glacio-fluvial deposits, is assigned to the Caledonia Glacigenic Group; within Northumberland, several different sub-groups are recognised according to the source of the material. North of the Cheviot massif, the till is assigned to the Borders Subgroup and to the south to the North Pennine Subgroup whilst that associated with the massif itself is classed as Cheviot Subgroup. Material originating from offshore (in terms of the present position of the coastline) is assigned to the North Sea Coast Subgroup, though the material along the coast from around

Beadnell Beadnell is a village and civil parish in Northumberland, England. It is situated about south-east of Bamburgh, on the North Sea coast, and has a population of 528(2001), increasing to 545 at the 2011 Census. It takes its name from the Anglo Sa ...

southwards is of mixed North Sea/Pennine provenance. The Pennine tills are generally dark grey reflecting the nature of the Carboniferous bedrock from which they largely originate.

Blown sand

Much of the coast is backed by areas of blown sand, notably at Ross Links south of Lindisfarne,

Druridge Bay Druridge Bay is a long bay on the North Sea in Northumberland, England, stretching from Amble in the north to Cresswell in the south. Druridge Bay Country Park is situated on the bay, and part of the bay (the section near the farmstead of Dru ...

, at

Lynemouth Lynemouth is a village in Northumberland, England, northeast of Ashington, close to the village of Ellington to the north west. It was built close to coal mines, including Lynemouth Colliery. Lynemouth and the surrounding industrial area feat ...

and to the north and south of Blyth.

Raised beach

Raised beach deposits are recorded at Spittal, Berwick-upon-Tweed, at Lindisfarne and around

Budle Bay Budle Bay is a wide bay on the North Sea in Northumberland, England, between Bamburgh to the southeast and Lindisfarne to the northwest. The bay is roughly square in plan opening to the North Sea along its northeastern side. Budle Point forms it ...

and elsewhere.BGS 1:50,000 scale geological map sheets (England and Wales series) sheet 1&2 Berwick-upon-Tweed and Norham & sheet 4 Holy Island

Peat

Large parts of Northumberland's uplands are blanketed by

peat Peat (), also known as turf (), is an accumulation of partially decayed vegetation or organic matter. It is unique to natural areas called peatlands, bogs, mires, moors, or muskegs. The peatland ecosystem covers and is the most efficient ...

Alluvium

The floors of the main river valleys are formed by

alluvium Alluvium (from Latin ''alluvius'', from ''alluere'' 'to wash against') is loose clay, silt, sand, or gravel that has been deposited by running water in a stream bed, on a floodplain, in an alluvial fan or beach, or in similar settings. ...

, sand, silts and gravel laid down by rivers and streams.

River terrace Fluvial terraces are elongated terraces that flank the sides of floodplains and fluvial valleys all over the world. They consist of a relatively level strip of land, called a "tread", separated from either an adjacent floodplain, other fluvial te ...

s are evident along the Tyne valley and three terraces are developed along that of the

River Tweed The River Tweed, or Tweed Water ( gd, Abhainn Thuaidh, sco, Watter o Tweid, cy, Tuedd), is a river long that flows east across the Border region in Scotland and northern England. Tweed cloth derives its name from its association with the ...

. Terraces are also developed along the course of the Till, Aln, Coquet, Font, Wansbeck and Breamish.

References

{{Geology of England , state=expanded Geography of Northumberland Geology of England