![Bedrock of Finland](https://upload.wikimedia.org/wikipedia/commons/1/1a/Bedrock_of_Finland.png)
The geology of Finland is made up of a mix of
geologically very young and very old materials. Common rock types are
orthogneiss
Gneiss ( ) is a common and widely distributed type of metamorphic rock. It is formed by high-temperature and high-pressure metamorphic processes acting on formations composed of igneous or sedimentary rocks. Gneiss forms at higher temperatures an ...
,
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 ...
,
metavolcanic
Metavolcanic rock is volcanic rock that shows signs of having experienced metamorphism. In other words, the rock was originally produced by a volcano, either as lava or tephra. The rock was then subjected to high pressure, high temperature or both ...
s and
metasedimentary
In geology, metasedimentary rock is a type of metamorphic rock. Such a rock was first formed through the deposition and solidification of sediment
Sediment is a naturally occurring material that is broken down by processes of weathering and e ...
rocks. On top of these lies a widespread thin layer of unconsolidated deposits formed in connection to the
Quaternary ice ages, for example
esker
An esker, eskar, eschar, or os, sometimes called an ''asar'', ''osar'', or ''serpent kame'', is a long, winding ridge of stratified sand and gravel, examples of which occur in glaciated and formerly glaciated regions of Europe and North Ame ...
s,
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 ...
and
marine clay
Marine clay is a type of clay found in coastal regions around the world. In the northern, deglaciated regions, it can sometimes be quick clay, which is notorious for being involved in landslides.
Marine clay is a particle of soil that is dedica ...
. The
topographic relief
Terrain or relief (also topographical relief) involves the vertical and horizontal dimensions of land surface. The term bathymetry is used to describe underwater relief, while hypsometry studies terrain relative to sea level. The Latin w ...
is rather subdued because mountain
massif
In geology, a massif ( or ) is a section of a planet's crust that is demarcated by faults or flexures. In the movement of the crust, a massif tends to retain its internal structure while being displaced as a whole. The term also refers to a ...
s were worn down to a
peneplain
390px, Sketch of a hypothetical peneplain formation after an orogeny.
In geomorphology and geology, a peneplain is a low-relief plain formed by protracted erosion. This is the definition in the broadest of terms, albeit with frequency the usage ...
long ago.
Precambrian shield
The
bedrock of
Finland
Finland ( fi, Suomi ; sv, Finland ), officially the Republic of Finland (; ), is a Nordic country in Northern Europe. It shares land borders with Sweden to the northwest, Norway to the north, and Russia to the east, with the Gulf of B ...
belongs to the
Fennoscandian Shield and was formed by a succession of
orogenies during the
Precambrian.
The oldest rocks of Finland, those of
Archean
The Archean Eon ( , also spelled Archaean or Archæan) is the second of four geologic eons of Earth's history, representing the time from . The Archean was preceded by the Hadean Eon and followed by the Proterozoic.
The Earth during the Arc ...
age, are found in the east and north. These rocks are chiefly
granitoid
A granitoid is a generic term for a diverse category of coarse-grained igneous rocks that consist predominantly of quartz, plagioclase, and alkali feldspar. Granitoids range from plagioclase-rich tonalites to alkali-rich syenites and from quartz- ...
s and
migmatitic gneiss
Gneiss ( ) is a common and widely distributed type of metamorphic rock. It is formed by high-temperature and high-pressure metamorphic processes acting on formations composed of igneous or sedimentary rocks. Gneiss forms at higher temperatures a ...
.
[ Rocks in central and western Finland originated or were emplaced during the Svecokarelian orogeny.][ Following this last orogeny ]rapakivi granite
Rapakivi granite is a hornblende-biotite granite containing large round crystals of orthoclase each with a rim of oligoclase (a variety of plagioclase). The name has come to be used most frequently as a textural term where it implies plagioclase r ...
s intruded
Intrusive rock is formed when magma penetrates existing rock, crystallizes, and solidifies underground to form '' intrusions'', such as batholiths, dikes, sills, laccoliths, and volcanic necks.Intrusive RocksIntrusive rocks accessdate: March 2 ...
various locations of Finland during the Mesoproterozoic
The Mesoproterozoic Era is a geologic era that occurred from . The Mesoproterozoic was the first era of Earth's history for which a fairly definitive geological record survives. Continents existed during the preceding era (the Paleoproterozoic), ...
and Neoproterozoic
The Neoproterozoic Era is the unit of geologic time from 1 billion to 538.8 million years ago.
It is the last era of the Precambrian Supereon and the Proterozoic Eon; it is subdivided into the Tonian, Cryogenian, and Ediacaran periods. It is prec ...
, especially in Åland
Åland ( fi, Ahvenanmaa: ; ; ) is an autonomous and demilitarised region of Finland since 1920 by a decision of the League of Nations. It is the smallest region of Finland by area and population, with a size of 1,580 km2, and a populat ...
and in the southeast.[ Jotnian sediments occur usually together with rapakivi granites.]
Mountains that existed in Precambrian time were eroded into a level terrain already during the Late Mesoproterozoic. With Proterozoic erosion amounting to tens of kilometers, many of the Precambrian rocks seen today in Finland are the "roots" of ancient massifs.[
As Finland is in the older part of the Fennoscandian Shield, its basement rocks are within three of the shield's older subdivisions known as domains: the Kola, Karelian and Svecofennian domains. This subdivision, established by Gaál and Gorbachev in 1987, is based on the different geological histories of the domains prior to their final amalgamation 1,800 million years ago.][
]
Kola Domain
The extreme northeast of Finland is part of the Kola Domain because it shows considerable affinity with the geology of the Kola Peninsula
sjd, Куэлнэгк нёа̄ррк
, image_name= Kola peninsula.png
, image_caption= Kola Peninsula as a part of Murmansk Oblast
, image_size= 300px
, image_alt=
, map_image= Murmansk in Russia.svg
, map_caption = Location of Murmansk Oblas ...
in Russia. Around Lake Inari
Lake Inari ( fi, Inarijärvi/Inarinjärvi, se, Anárjávri, smn, Aanaarjävri, sms, Aanarjäuʹrr, sv, Enare träsk, no, Enaresjøen) is the largest lake in Sápmi and the third-largest lake in Finland. It is located in the northern part of L ...
there are paragneiss
Gneiss ( ) is a common and widely distributed type of metamorphic rock. It is formed by high-temperature and high-pressure metamorphic processes acting on formations composed of igneous or sedimentary rocks. Gneiss forms at higher temperatures an ...
, orthogneiss
Gneiss ( ) is a common and widely distributed type of metamorphic rock. It is formed by high-temperature and high-pressure metamorphic processes acting on formations composed of igneous or sedimentary rocks. Gneiss forms at higher temperatures an ...
and greenstone belts. Rocks in this part of Finland are of Archean
The Archean Eon ( , also spelled Archaean or Archæan) is the second of four geologic eons of Earth's history, representing the time from . The Archean was preceded by the Hadean Eon and followed by the Proterozoic.
The Earth during the Arc ...
and Proterozoic age.[
To the south and west of Lake Inari lies an elongate and arcuate zone of granulite rock known as the Lapland Granulite Belt. The belt is up to 80 km wide. The main rocks of the belt are migmatized ]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 ...
and argillite
:''"Argillite" may also refer to Argillite, Kentucky.''
Argillite () is a fine-grained sedimentary rock composed predominantly of indurated clay particles. Argillaceous rocks are basically lithified muds and oozes. They contain variable amounts ...
s. Studies of detrital
Detritus (; adj. ''detrital'' ) is particles of rock derived from pre-existing rock through weathering and erosion.Essentials of Geology, 3rd Ed, Stephen Marshak, p G-7 A fragment of detritus is called a clast.Essentials of Geology, 3rd Ed, Stephe ...
zircon
Zircon () is a mineral belonging to the group of nesosilicates and is a source of the metal zirconium. Its chemical name is zirconium(IV) silicate, and its corresponding chemical formula is Zr SiO4. An empirical formula showing some of t ...
show that the sedimentary protolith
A protolith () is the original, unmetamorphosed rock from which a given metamorphic rock is formed.
For example, the protolith of a slate is a shale or mudstone. Metamorphic rocks can be derived from any other kind of non-metamorphic rock and ...
of the metamorphic rocks of the belt could not be more than 2900–1940 million years old. The belt has norite
Norite is a mafic intrusive igneous rock composed largely of the calcium-rich plagioclase labradorite, orthopyroxene, and olivine. The name ''norite'' is derived from ''Norge'', the Norwegian name for Norway.
Norite also known as orthopyrox ...
and enderbite intrusions of calc-alkaline chemistry.
Karelian Domain
The Karelian Domain, or Karelian Block, makes up most of the bedrock of the northeastern part of Finland[Vaasjoki ''et al''. 2005, pp. 4–5.] extending into nearby areas of Russia.[Sorjonen-Ward & Luukkonen 2005, pp. 22–23.] The Karelian domain is made up of a collage of rock formed during Archean
The Archean Eon ( , also spelled Archaean or Archæan) is the second of four geologic eons of Earth's history, representing the time from . The Archean was preceded by the Hadean Eon and followed by the Proterozoic.
The Earth during the Arc ...
and Paleoproterozoic
The Paleoproterozoic Era (;, also spelled Palaeoproterozoic), spanning the time period from (2.5–1.6 Ga), is the first of the three sub-divisions ( eras) of the Proterozoic Eon. The Paleoproterozoic is also the longest era of the Earth's ...
times.[Vaasjoki ''et al''. 2005, pp. 6–7.] The boundary to the Kola Domain is made up of a gently dipping décollement
Décollement () is a gliding plane between two rock masses, also known as a basal detachment fault. Décollements are a deformational structure, resulting in independent styles of deformation in the rocks above and below the fault. They are ass ...
where the Lapland Granulite Belt has been thrust southward over rocks of the Karelian Domain.[
Archean rocks in the Karelian Domain are north-south medium grade greenstone and ]metasediment
In geology, metasedimentary rock is a type of metamorphic rock. Such a rock was first formed through the deposition and solidification of sediment
Sediment is a naturally occurring material that is broken down by processes of weathering and e ...
ary belts. The belts are intruded by granitoids
A granitoid is a generic term for a diverse category of coarse-grained igneous rocks that consist predominantly of quartz, plagioclase, and alkali feldspar. Granitoids range from plagioclase-rich tonalites to alkali-rich syenites and from quart ...
, usually monzogranite
Monzogranites are biotite granite rocks that are considered to be the final fractionation product of magma. Monzogranites are characteristically felsic (SiO2 > 73%, and FeO + MgO + TiO2 < 2.4), weakly granodiorite
Granodiorite () is a coarse-grained ( phaneritic) intrusive igneous rock similar to granite, but containing more plagioclase feldspar than orthoclase feldspar.
The term banatite is sometimes used informally for various rocks ranging from gr ...
. Besides these belts and intrusions there is also metasedimentary
In geology, metasedimentary rock is a type of metamorphic rock. Such a rock was first formed through the deposition and solidification of sediment
Sediment is a naturally occurring material that is broken down by processes of weathering and e ...
gneiss
Gneiss ( ) is a common and widely distributed type of metamorphic rock. It is formed by high-temperature and high-pressure metamorphic processes acting on formations composed of igneous or sedimentary rocks. Gneiss forms at higher temperatures a ...
formed at intermediate pressures.[ Along the central part of the ]Finland–Russia border
The Finnish–Russian border is the roughly north–south international border between the Republic of Finland and the Russian Federation. Some long, it runs mostly through uninhabited taiga forests and sparsely populated rural areas, not fo ...
lies the Belomorian terrane, a subunit of the Karelian Domain thought to have formed by a collision
In physics, a collision is any event in which two or more bodies exert forces on each other in a relatively short time. Although the most common use of the word ''collision'' refers to incidents in which two or more objects collide with great fo ...
between the Kola Domain with the Karelian Domain in the Paleoproterozoic
The Paleoproterozoic Era (;, also spelled Palaeoproterozoic), spanning the time period from (2.5–1.6 Ga), is the first of the three sub-divisions ( eras) of the Proterozoic Eon. The Paleoproterozoic is also the longest era of the Earth's ...
.[Sorjonen-Ward & Luukkonen 2005, pp. 24–25.] This collision marked the final merger of both crustal blocks.[Sorjonen-Ward & Luukkonen 2005, pp. 70–71.] Rocks of the Belomorian terrane, like the granitoid
A granitoid is a generic term for a diverse category of coarse-grained igneous rocks that consist predominantly of quartz, plagioclase, and alkali feldspar. Granitoids range from plagioclase-rich tonalites to alkali-rich syenites and from quartz- ...
gneiss
Gneiss ( ) is a common and widely distributed type of metamorphic rock. It is formed by high-temperature and high-pressure metamorphic processes acting on formations composed of igneous or sedimentary rocks. Gneiss forms at higher temperatures a ...
es common there, are of high grade.[
The Central Lapland granitoid complex covers up much of the interior of northern Finland. These rocks were formed in the final stages of the Svecofennian orogeny and are mostly made up of coarse-grained granites.][Nironen 2005, pp. 457–458.] An alignment of granitoid intrusions southeast of Oulu likely shares the same origin.[Nironen 2005, pp. 459–460.]
Finland's three ophiolite
An ophiolite is a section of Earth's oceanic crust and the underlying upper mantle that has been uplifted and exposed above sea level and often emplaced onto continental crustal rocks.
The Greek word ὄφις, ''ophis'' (''snake'') is found ...
s crop out within the Karelian Domain. These are the Jormua, Outokumpu and Nuttio ophiolite complexes.[ All of them were emplaced in Paleoproterozoic times.][Peltonen 2005, pp. 241–242.] The Jormua and Outokumpu ophiolites lie parallel to and near the boundary with the Svecofennian Domain.[Peltonen 2005, pp. 239–240.] Also towards the border with the Svecovefennian Domain there is a series of metamorphosed
Metamorphic rocks arise from the transformation of existing rock to new types of rock in a process called metamorphism. The original rock (protolith) is subjected to temperatures greater than and, often, elevated pressure of or more, causi ...
Archean rocks that are stacked into an imbrication pattern.[
]
Svecofennian Domain
The southwestern part of Finland is mainly made up of rocks of the Svecofennian Domain or Svecofennian orogen.[ These rocks are invariably of Proterozoic age. Its boundary with the Karelian Domain (of mixed ]Archean
The Archean Eon ( , also spelled Archaean or Archæan) is the second of four geologic eons of Earth's history, representing the time from . The Archean was preceded by the Hadean Eon and followed by the Proterozoic.
The Earth during the Arc ...
and Paleoproterozoic
The Paleoproterozoic Era (;, also spelled Palaeoproterozoic), spanning the time period from (2.5–1.6 Ga), is the first of the three sub-divisions ( eras) of the Proterozoic Eon. The Paleoproterozoic is also the longest era of the Earth's ...
rocks) is a northwest-southeast diagonal.[ ]Plutonic rock
Intrusive rock is formed when magma penetrates existing rock, crystallizes, and solidifies underground to form '' intrusions'', such as batholiths, dikes, sills, laccoliths, and volcanic necks.Intrusive RocksIntrusive rocks accessdate: March ...
s that formed during accretion of volcanic arcs or continental collisions of the Svecofennian orogeny are common in Svecofennian Domain.[Nironen 2005, pp. 445–446.][Nironen 2005, pp. 447–448.] Among these rocks the largest grouping is the Central Finland granitoid complex covering up much of Central Finland
Central Finland ( fi, Keski-Suomi; sv, Mellersta Finland) is a region ( / ) in Finland. It borders the regions of Päijät-Häme, Pirkanmaa, South Ostrobothnia, Central Ostrobothnia, North Ostrobothnia, North Savo, and South Savo. The city o ...
, Southern Ostrobothnia
South Ostrobothnia ( fi, Etelä-Pohjanmaa; sv, Södra Österbotten) is one of the 19 regions of Finland. It borders the regions of Ostrobothnia, Central Ostrobothnia, Central Finland, Pirkanmaa, and Satakunta. Among the Finnish regions, South ...
and Pirkanmaa
Pirkanmaa (; sv, Birkaland; la, Birkaria, link=no), also known as ''Tampere Region'' in government documents, is a region of Finland. It borders the regions of Satakunta, South Ostrobothnia, Central Finland, Päijät-Häme, Kanta-Häme an ...
.[ Granitoids that intruded in the aftermath of the Svercofennian orogeny are common in southern Finland occurring mostly within ca. 100 km of the Gulf of Finland or Lake Ladoga.][Nironen 2005, pp. 455–456.] These so-called Lateorogenic granites are distinguished by usually containing garnet
Garnets () are a group of silicate minerals that have been used since the Bronze Age as gemstones and abrasives.
All species of garnets possess similar physical properties and crystal forms, but differ in chemical composition. The different s ...
and cordierite
Cordierite (mineralogy) or iolite (gemology) is a magnesium iron aluminium cyclosilicate. Iron is almost always present and a solid solution exists between Mg-rich cordierite and Fe-rich sekaninaite with a series formula: to . A high-temperat ...
and being accompanied by rather few rocks of mafic
A mafic mineral or rock is a silicate mineral or igneous rock rich in magnesium and iron. Most mafic minerals are dark in color, and common rock-forming mafic minerals include olivine, pyroxene, amphibole, and biotite. Common mafic rocks incl ...
and intermediate composition.[ Scattered small granitoids crop out within the same zone. Formed 1810–1770 million years ago, these are the youngest granitoids in southern Finland associated with the Svecofennian orogeny.][
]
Rapakivi granite and Jotnian sediment
Jotnian
In north European geology, Jotnian sediments are a group of Precambrian rocks more specifically assigned to the Mesoproterozoic Era ( Riphean), albeit some might be younger. Jotnian sediments include the oldest known sediments in the Baltic area ...
sediments are the oldest known sediments in the Baltic area that have not been subject to significant metamorphism
Metamorphism is the transformation of existing rock (the protolith) to rock with a different mineral composition or texture. Metamorphism takes place at temperatures in excess of , and often also at elevated pressure or in the presence of ch ...
.
These sediments are typically quartz
Quartz is a hard, crystalline mineral composed of silica ( silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical ...
-rich sandstone
Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks.
Most sandstone is composed of quartz or feldspar (both silicates ...
s, siltstones, arkose, shale and conglomerates.[Kohonen & Rämö 2005, p. 567.] The characteristic red colour of Jotnian sediments is due to their deposition in subaerial (e.g. non-marine) conditions.[ In Finland, Jotnian sediments occur in the Muhos Graben near Oulu at the northeastern end of the Gulf of Bothnia][ and further south near the coast at ]Satakunta
Satakunta (in both Finnish and Swedish, ) is a region ( / ) of Finland, part of the former Western Finland Province. It borders the regions of Southwest Finland, Pirkanmaa, South Ostrobothnia and Ostrobothnia. The capital city of the region ...
. Jotnian rocks are also found offshore between Finland and Sweden in the Gulf of Bothnia and the Åland Sea including South Kvarken. Known Jotnian rocks at the Åland Sea are sandstones belonging to the informally defined Söderarm Formation. Above these there are Upper Riphean and Vendian
The Ediacaran Period ( ) is a geological period that spans 96 million years from the end of the Cryogenian Period 635 million years ago (Mya), to the beginning of the Cambrian Period 538.8 Mya. It marks the end of the Proterozoic Eon, and the ...
sandstones and shales. There is evidence suggesting that Jotnian rocks, or even a Jotnian platform
Platform may refer to:
Technology
* Computing platform, a framework on which applications may be run
* Platform game, a genre of video games
* Car platform, a set of components shared by several vehicle models
* Weapons platform, a system or ...
, once covered much of Fennoscandia and were not restricted to a few localities like today. The limited geographical extent of Jotnian sediments at present is indebted to their erosion
Erosion is the action of surface processes (such as water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust, and then transports it to another location where it is deposited. Erosion is dis ...
over geological time
The geologic time scale, or geological time scale, (GTS) is a representation of time based on the rock record of Earth. It is a system of chronological dating that uses chronostratigraphy (the process of relating strata to time) and geochron ...
.[ Sedimentary rocks as old as the Jotnian sediments have a low preservation potential.]
The distribution of some Jotnian sediments is spatially associated with the occurrence of rapakivi granite.[ Korja and co-workers (1993) claim the Jotnian sediment–rapakivi granite coincidence at the Gulf of Finland and the Gulf of Bothnia is related to the existence of thin crust at these locations.][
]
Alkaline rocks
Small outcrops of alkaline rocks, carbonatite
Carbonatite () is a type of intrusive or extrusive igneous rock defined by mineralogic composition consisting of greater than 50% carbonate minerals. Carbonatites may be confused with marble and may require geochemical verification.
Carbonati ...
s and kimberlite
Kimberlite is an igneous rock and a rare variant of peridotite. It is most commonly known to be the main host matrix for diamonds. It is named after the town of Kimberley in South Africa, where the discovery of an diamond called the Star of S ...
s exist in Finland[O'Brien ''et al''. 2005, pp. 607–608.] including the western and southernmost outcrops of the 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 ...
-aged Kola Alkaline Province
The Kola Alkaline Province or Kola Alkaline Carbonatite Province is a discontiguous group of unusual igneous rocks centered in the Kola Peninsula of Russia and with ouliers in nearby areas of Finland and in Arkhangelsk Oblast across the White Se ...
.[ The Kola Alkaline Province is commonly presumed to represent an igneous hotspot created by a ]mantle plume
A mantle plume is a proposed mechanism of convection within the Earth's mantle, hypothesized to explain anomalous volcanism. Because the plume head partially melts on reaching shallow depths, a plume is often invoked as the cause of volcanic hot ...
. Carbonatites in Finland have wide range in ages but they all derive from a "well-mixed" portion of the upper mantle
The upper mantle of Earth is a very thick layer of rock inside the planet, which begins just beneath the crust (at about under the oceans and about under the continents) and ends at the top of the lower mantle at . Temperatures range from appr ...
. The Siilinjärvi carbonatite complex of Archean age is one of the Earth's oldest carbonatites.[ All known kimberlites are concentrated near the towns of Kuopio and ]Kaavi
Kaavi is a municipality of Finland. It is located in the Northern Savonia region. Kaavi is also a part of historical Karelia. The municipality has a population of () and covers an area of of which is water. The population density is . It is fr ...
. These are grouped in two clusters and include diatreme
A diatreme, sometimes known as a maar-diatreme volcano, is a volcanic pipe formed by a gaseous explosion. When magma rises up through a crack in Earth's crust and makes contact with a shallow body of groundwater, rapid expansion of heated wate ...
s and dykes.
Caledonian rocks
The youngest rocks in Finland are those found near Kilpisjärvi
Kilpisjärvi (; se, Gilbbesjávri ) is a village in the municipality of Enontekiö, Lapland, Finland. It is located in Finland's northern "arm" near the very northwesternmost point of Finland.
Although Kilpisjärvi is one of the largest village ...
in Enontekiö
Enontekiö (; sme, Eanodat ; sv, Enontekis; smn, Iänudâh; sms, Jeänõk) is a municipality in the Finnish part of Lapland with approx. inhabitants. It is situated in the outermost northwest of the country and occupies a large and very spars ...
(the northwesternmost part of the country's northwestern arm
In human anatomy, the arm refers to the upper limb in common usage, although academically the term specifically means the upper arm between the glenohumeral joint (shoulder joint) and the elbow joint. The distal part of the upper limb between th ...
). These rocks belong to the Scandinavian Caledonides
The Scandinavian Caledonides are the vestiges of an ancient, today deeply eroded orogenic belt formed during the Silurian–Devonian continental collision of Baltica and Laurentia, which is referred to as the Scandian phase of the Caledonian or ...
that assembled in Paleozoic
The Paleozoic (or Palaeozoic) Era is the earliest of three geologic eras of the Phanerozoic Eon.
The name ''Paleozoic'' ( ;) was coined by the British geologist Adam Sedgwick in 1838
by combining the Greek words ''palaiós'' (, "old") and ' ...
times.[ During 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 ...
Finland was likely a sunken foreland basin covered by sediments; subsequent uplift and erosion would have eroded all of these sediments. In Finland, Caledonian nappe
In geology, a nappe or thrust sheet is a large sheetlike body of rock that has been moved more than or above a thrust fault from its original position. Nappes form in compressional tectonic settings like continental collision zones or on the o ...
s overlie shield rocks of Archean age.[ Despite occurring in about the same area the Scandinavian Caledonides and the modern Scandinavian Mountains are unrelated.]
Quaternary deposits
The ice sheet
In glaciology, an ice sheet, also known as a continental glacier, is a mass of glacial ice that covers surrounding terrain and is greater than . The only current ice sheets are in Antarctica and Greenland; during the Last Glacial Period at La ...
that covered Finland intermittently during the Quaternary grew out from the Scandinavian Mountains. By some estimates the Quaternary glaciers eroded away on average 25 m of rock in Finland,[ with the degree of erosion being highly variable.] Some of the material eroded in Finland has ended up in Germany, Poland, Russia and the Baltic states.[ Ground ]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 ...
left by the Quaternary ice sheets is ubiquitous in Finland.[ Relative to the rest of Finland, the southern coastal areas have a thin and patchy cover of till evidencing a more prominent role of glacial erosion in the area, whereas Ostrobothnia and parts of Lapland stand out for their thick till cover. The central parts of the Weichsel ice sheet had cold-based conditions during the times of maximum extent. Therefore, pre-existing landforms and deposits in northern Finland escaped glacial erosion and are now particularly well preserved.] Northwest to southeast movement of the ice has left a field of aligned drumlin
A drumlin, from the Irish word ''droimnín'' ("littlest ridge"), first recorded in 1833, in the classical sense is an elongated hill in the shape of an inverted spoon or half-buried egg formed by glacial ice acting on underlying unconsolidated ...
s in central Lapland. Ribbed moraines found in the same area reflect a later west to east change in movement of the ice.[
During the last deglaciation, the first part of Finland to become ice-free was the southeastern coast; this occurred shortly before the ]Younger Dryas
The Younger Dryas (c. 12,900 to 11,700 years BP) was a return to glacial conditions which temporarily reversed the gradual climatic warming after the Last Glacial Maximum (LGM, c. 27,000 to 20,000 years BP). The Younger Dryas was the last stag ...
cold-spell 12,700 years before present
Before Present (BP) years, or "years before present", is a time scale used mainly in archaeology, geology and other scientific disciplines to specify when events occurred relative to the origin of practical radiocarbon dating in the 1950s. Becau ...
(BP). While the ice cover continued to retreat in the southeast after Younger Dryas, retreat also occurred in the east and northeast. The retreat was fastest from the southeast resulting in the lower course of the Tornio
Tornio (; sv, Torneå; sme, Duortnus ; smn, Tuárnus) is a city and municipality in Lapland, Finland. The city forms a cross-border twin city together with Haparanda on the Swedish side. The municipality covers an area of , of which is ...
river in northwest Finland becoming the last part of the country to be ice-free. Finally, by 10,100 years BP, the ice cover had all but left Finland, retreating to Sweden and Norway before fading away. Ice retreat was accompanied by the formation of esker
An esker, eskar, eschar, or os, sometimes called an ''asar'', ''osar'', or ''serpent kame'', is a long, winding ridge of stratified sand and gravel, examples of which occur in glaciated and formerly glaciated regions of Europe and North Ame ...
s and the dispersal of fine-grained sediment deposited as varve
A varve is an annual layer of sediment or sedimentary rock.
The word 'varve' derives from the Swedish word ''varv'' whose meanings and connotations include 'revolution', 'in layers', and 'circle'. The term first appeared as ''Hvarfig lera'' (va ...
s.[
As the ice sheet became thinner and retreated, the land began to rise due to ]post-glacial rebound
Post-glacial rebound (also called isostatic rebound or crustal rebound) is the rise of land masses after the removal of the huge weight of ice sheets during the last glacial period, which had caused isostatic depression. Post-glacial rebound ...
. Much of Finland was under water when the ice retreated and was gradually uplifted in a process that continues today.[ Not all areas were drowned at the same time and it is estimated that, at one time or another, about 62% has been under water.] The maximum height of the ancient shoreline varied from region to region: in southern Finland 150 to 160 m, in central Finland about 200 m and in eastern Finland up to 220 m. Once free of ice and water, soils have developed in Finland. Podzol
In soil science, podzols are the typical soils of coniferous or boreal forests and also the typical soils of eucalypt forests and heathlands in southern Australia. In Western Europe, podzols develop on heathland, which is often a construct of ...
s with till as parent material
Parent material is the underlying geological material (generally bedrock or a superficial or drift deposit) in which soil horizons form. Soils typically inherit a great deal of structure and minerals from their parent material, and, as such, are ...
now cover about 60% of Finland's land area.
Economic geology
Mining for metals in Finland began in 1530 at the Ojamo iron mine[ but mining in the country was minimal until the 1930s.] The Outokumpu
Outokumpu Oyj is a group of international companies headquartered in Helsinki, Finland, employing 10,600 employees in more than 30 countries. Outokumpu is the largest producer of stainless steel in Europe and the second largest producer in the A ...
ore
Ore is natural rock or sediment that contains one or more valuable minerals, typically containing metals, that can be mined, treated and sold at a profit.Encyclopædia Britannica. "Ore". Encyclopædia Britannica Online. Retrieved 7 Apr ...
deposit, discovered in 1910, was key to the development of mining in Finland during the 20th century. When Outokumpu opened in 1910 it was Finland's first sulphide ore to be mined. This mine closed in 1989. Another important Finnish mining resource was the nickel
Nickel is a chemical element with symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive but large pieces are slow ...
of Petsamo, which was mined by Canadian INCO
Vale Canada Limited (formerly Vale Inco, CVRD Inco and Inco Limited; for corporate branding purposes simply known as "Vale" and pronounced in English) is a wholly owned subsidiary of the Brazilian mining company Vale. Vale's nickel mining and ...
from the 1920s onwards. Petsamo and its mines were, however, lost to the Soviet Union
The Soviet Union,. officially the Union of Soviet Socialist Republics. (USSR),. was a List of former transcontinental countries#Since 1700, transcontinental country that spanned much of Eurasia from 1922 to 1991. A flagship communist state, ...
in 1944 as result of the Moscow Armistice
The Moscow Armistice was signed between Finland on one side and the Soviet Union and United Kingdom on the other side on 19 September 1944, ending the Continuation War. The Armistice restored the Moscow Peace Treaty of 1940, with a number of mo ...
.[
From 2001 to 2004 the number of metallic ores being mined dropped from eleven to the following four:][
* Pyhäsalmi ]zinc
Zinc is a chemical element with the symbol Zn and atomic number 30. Zinc is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodi ...
mine, Immet Mining Corporations (Canadian financed)
*Nivala
Nivala is a town and municipality of Finland. It is located in the Northern Ostrobothnia region. The town has a population of
() and covers an area of of
which
is water. The population density is
. The municipality is unilingually Finnish.
Ge ...
nickel
Nickel is a chemical element with symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive but large pieces are slow ...
mine, Outokumpu
*Keminmaa
Keminmaa (until 1979 Kemin maalaiskunta) ( smn, Kiemâeennâm; sms, Ǩeeʹmmjânnam) is a municipality of Finland.
The municipality has a population of
() and covers an area of of
which
is water. The population density is
.
Geography
Neighbou ...
chromium mine, Avesta Polarit
*Sodankylä
Sodankylä (; sme, Soađegilli ; smn, Suáđigil; sms, Suäʹđjel) is a municipality of Finland. It is located in the region of Lapland, and lies at the northern end of Highway 5 ( E63) and along Highway 4 ( E75). The Kitinen River flows nea ...
gold mine, ScanMining (Swedish financed)
There are some uranium resources in Finland, but to date no commercially viable deposits have been identified for exclusive mining of uranium. In the Karelian Domain, there are various layered mafic intrusions of early Paleoproterozoic age that have been exploited for vanadium.[Iljina & Hanski 2005, p. 103.]
Most of Finland's metallic ores formed in the Paleoproterozoic
The Paleoproterozoic Era (;, also spelled Palaeoproterozoic), spanning the time period from (2.5–1.6 Ga), is the first of the three sub-divisions ( eras) of the Proterozoic Eon. The Paleoproterozoic is also the longest era of the Earth's ...
during the Svecofennian orogeny or during the period of complex extensional tectonics that preceded it.
Non-metallic resources
Non-metallic resources Finland include phosphorus
Phosphorus is a chemical element with the symbol P and atomic number 15. Elemental phosphorus exists in two major forms, white phosphorus and red phosphorus, but because it is highly reactive, phosphorus is never found as a free element on Ear ...
that has been mined at the Siilinjärvi
Siilinjärvi () is a municipality of Finland. It is located in Northern Savonia, north of the city of Kuopio, which largely surrounds Siilinjärvi. Another neighbour municipality with Kuopio is Lapinlahti. The name, in Finnish, apparently transla ...
carbonatite since 1979, the outcrop being originally discovered in 1950.[ The bedrock of Finland contain various types of gemstones.][ The Lahtojoki kimberlite has gem quality ]garnet
Garnets () are a group of silicate minerals that have been used since the Bronze Age as gemstones and abrasives.
All species of garnets possess similar physical properties and crystal forms, but differ in chemical composition. The different s ...
and diamond xenocryst
A xenolith ("foreign rock") is a rock fragment ( country rock) that becomes enveloped in a larger rock during the latter's development and solidification. In geology, the term ''xenolith'' is almost exclusively used to describe inclusions in ign ...
s.[O'Brien ''et al''. 2005, pp. 637–638.]
Finland has a thriving quarrying industry. Finnish dimension stone has been used historically for buildings in Helsinki and imperial Russia's Saint Petersburg
Saint Petersburg ( rus, links=no, Санкт-Петербург, a=Ru-Sankt Peterburg Leningrad Petrograd Piter.ogg, r=Sankt-Peterburg, p=ˈsankt pʲɪtʲɪrˈburk), formerly known as Petrograd (1914–1924) and later Leningrad (1924–1991), i ...
and Reval
Tallinn () is the most populous and capital city of Estonia. Situated on a bay in north Estonia, on the shore of the Gulf of Finland of the Baltic Sea, Tallinn has a population of 437,811 (as of 2022) and administratively lies in the Harju ''m ...
. Today, the main importers of Finnish stone are China, Germany, Italy and Sweden. The dimension stone quarried in Finland includes granites, such as the wiborgite variety of rapakivi granite, and marble
Marble is a metamorphic rock composed of recrystallized carbonate minerals, most commonly calcite or dolomite. Marble is typically not foliated (layered), although there are exceptions. In geology, the term ''marble'' refers to metamorphose ...
. Soapstone
Soapstone (also known as steatite or soaprock) is a talc-schist, which is a type of metamorphic rock. It is composed largely of the magnesium rich mineral talc. It is produced by dynamothermal metamorphism and metasomatism, which occur in the ...
from Finland's schist
Schist ( ) is a medium-grained metamorphic rock showing pronounced schistosity. This means that the rock is composed of mineral grains easily seen with a low-power hand lens, oriented in such a way that the rock is easily split into thin flakes ...
zone is also quarried for use in ovens.
See also
*Salpausselkä
Salpausselkä (; "Bar Ridge") is an extensive ridge system left by the ice age in Southern Finland. It is a large terminal moraine formation that formed in front of the Baltic ice lake during the Younger Dryas period about 12,250–10,400 years ...
Notes
References
;Bibliography
*
:*Iljina, M.; Hanski, E. "Layered Mafic Intrusions of the Tornio-Näränkävaara Belt". pp. 100–137
:*Kohonen, J.; Rämö, O.T. "Sedimentary Rocks, Diabases, and Late Cratonic Evolution". pp. 563–603.
:*Nironen, M. "Proterozoic Orogenic Granitoid Rocks". pp. 442–479.
:*O'Brien, H.E.; Peltonen, P.; Vartiainen, H. "Kimberlites, Carbonantites, and Alkaline Rocks". pp. 237–277.
:*Peltonen, P. "Ophiolites". pp. 237–277.
:*Sorjonen-Ward, P.; Luukkonen, E.J. "Archean Rocks". pp. 18–99.
:*Vaasjoki, M.; Korsman, K.; Koistinen, T. "Overview". pp. 1–17.
External links
{{Geology of Europe