![Loop Head - geograph](https://upload.wikimedia.org/wikipedia/commons/4/41/Loop_Head_-_geograph.org.uk_-_12618.jpg)
The geology of Ireland consists of the study of the rock formations on the island of
Ireland
Ireland ( ; ga, Éire ; Ulster Scots dialect, Ulster-Scots: ) is an island in the Atlantic Ocean, North Atlantic Ocean, in Northwestern Europe, north-western Europe. It is separated from Great Britain to its east by the North Channel (Grea ...
. It includes rocks from every age from
Proterozoic
The Proterozoic () is a geological eon spanning the time interval from 2500 to 538.8million years ago. It is the most recent part of the Precambrian "supereon". It is also the longest eon of the Earth's geologic time scale, and it is subdivided ...
to
Holocene
The Holocene ( ) is the current geological epoch. It began approximately 11,650 cal years Before Present (), after the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene togethe ...
and a large variety of different rock types is represented. The
basalt
Basalt (; ) is an aphanite, 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 planetary surface, surface of a terrestrial ...
columns of the
Giant's Causeway
The Giant's Causeway is an area of about 40,000 interlocking basalt columns, the result of an ancient volcanic fissure eruption. It is located in County Antrim on the north coast of Northern Ireland, about three miles (5 km) northeast of ...
together with geologically significant sections of the adjacent coast have been declared a
World Heritage Site
A World Heritage Site is a landmark or area with legal protection by an international convention administered by the United Nations Educational, Scientific and Cultural Organization (UNESCO). World Heritage Sites are designated by UNESCO for h ...
. The geological detail follows the major events in Ireland's past based on the geological timescale.
Timeline
![SlieveLeague1](https://upload.wikimedia.org/wikipedia/commons/7/78/SlieveLeague1.jpg)
The oldest known Irish
rock
Rock most often refers to:
* Rock (geology), a naturally occurring solid aggregate of minerals or mineraloids
* Rock music, a genre of popular music
Rock or Rocks may also refer to:
Places United Kingdom
* Rock, Caerphilly, a location in Wales ...
is about 1.7 billion years old and is found on
Inishtrahull Island
Inishtrahull ( ga, Inis Trá Tholl, possibly "island of the empty beach" or "island of the yonder beach") is the Extreme points of Ireland, most northerly island of Ireland. It has an area of and lies about northeast of Malin Head, County Do ...
off the north coast of
Ulster
Ulster (; ga, Ulaidh or ''Cúige Uladh'' ; sco, label= Ulster Scots, Ulstèr or ''Ulster'') is one of the four traditional Irish provinces. It is made up of nine counties: six of these constitute Northern Ireland (a part of the United King ...
. Outcrops at
Annagh Head Annagh or Anagh may refer to:
Places
Republic of Ireland
* Annagh, County Cavan, townland
* Annagh, townland in Kilkenny West
Kilkenny West (), previously Maherquirke or Dillons country, is a barony in west County Westmeath, Ireland. It wa ...
on the
Mullet Peninsula
The Mullet Peninsula ( ga, Leithinis an Mhuirthead)—also known as the Mullet (''an Mhuirthead'') and sometimes as the Erris Peninsula—is a peninsula in the barony of Erris in County Mayo, Ireland. As of 2016 it has a population of 3963. I ...
are almost as old. In other parts of Donegal, scientists have discovered rocks that originated as
glacial
A glacial period (alternatively glacial or glaciation) is an interval of time (thousands of years) within an ice age that is marked by colder temperatures and glacier advances. Interglacials, on the other hand, are periods of warmer climate betw ...
deposits, demonstrating that at this early period, part of what was to become Ireland was in the grip of an
ice age
An ice age is a long period of reduction in the temperature of Earth's surface and atmosphere, resulting in the presence or expansion of continental and polar ice sheets and alpine glaciers. Earth's climate alternates between ice ages and gree ...
. However, because of the effects of later upheavals, it is almost impossible to sequence these early rock layers correctly.
About 600 million years ago, at the end of the
Precambrian
The Precambrian (or Pre-Cambrian, sometimes abbreviated pꞒ, or Cryptozoic) is the earliest part of Earth's history, set before the current Phanerozoic Eon. The Precambrian is so named because it preceded the Cambrian, the first period of the ...
super-eon, what would later become the Irish landmass was in two parts, with one half on the north-western side of the
Iapetus Ocean
The Iapetus Ocean (; ) was an ocean that existed in the late Neoproterozoic and early Paleozoic eras of the geologic timescale (between 600 and 400 million years ago). The Iapetus Ocean was situated in the southern hemisphere, between the paleoco ...
in
Laurentia
Laurentia or the North American Craton is a large continental craton that forms the ancient geological core of North America. Many times in its past, Laurentia has been a separate continent, as it is now in the form of North America, although ...
and the other on the south-eastern side in the micro-continent
Avalonia
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 Wester ...
, both at a
latitude
In geography, latitude is a coordinate that specifies the north– south position of a point on the surface of the Earth or another celestial body. Latitude is given as an angle that ranges from –90° at the south pole to 90° at the north pol ...
of around 80° South, close to what is now northwest Africa. From the evidence of the
Oldhamia
''Oldhamia'' is an ichnogenus describing burrows produced by worm-like organisms mining underneath microbial mats. It was common from the Early Cambrian deep-water deposits.
The Ediacaran species ''Oldhamia recta'' are body fossils of a rod-lik ...
fossils found at
Bray Head
Bray Head ( ga, Ceann Bhré) is a hill and headland located in northern County Wicklow, Ireland, between the towns of Bray and Greystones. It forms part of the Wicklow Mountains and is a popular spot with hillwalkers. At the top of the head i ...
in
Leinster
Leinster ( ; ga, Laighin or ) is one of the provinces of Ireland, situated in the southeast and east of Ireland. The province comprises the ancient Kingdoms of Meath, Leinster and Osraige. Following the 12th-century Norman invasion of Ir ...
, both parts of Ireland were below sea level at this time.
Over the next 150 million years, these two parts moved towards each other, eventually uniting about 440 million years ago.
Fossil
A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...
s discovered near
Clogherhead
Clogherhead () is a fishing village in County Louth, Ireland. Located in a natural bay on the east coast it is bordered by the villages of Annagassan to the north and Termonfeckin to the south. It has a population of 2,145 according to the 2 ...
,
County Louth
County Louth ( ; ga, An Lú) is a coastal county in the Eastern and Midland Region of Ireland, within the province of Leinster. Louth is bordered by the counties of Meath to the south, Monaghan to the west, Armagh to the north and Down to the ...
, show the coming together of shoreline
fauna
Fauna is all of the animal life present in a particular region or time. The corresponding term for plants is ''flora'', and for fungi, it is '' funga''. Flora, fauna, funga and other forms of life are collectively referred to as '' biota''. Zoo ...
from both sides of the original dividing ocean. The mountains of northwest Ireland were formed during the collision, as was the
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 undergro ...
that is found in locations in
Donegal Donegal may refer to:
County Donegal, Ireland
* County Donegal, a county in the Republic of Ireland, part of the province of Ulster
* Donegal (town), a town in County Donegal in Ulster, Ireland
* Donegal Bay, an inlet in the northwest of Ireland b ...
and Wicklow. The Irish landmass was now above sea level and lying near the
equator
The equator is a circle of latitude, about in circumference, that divides Earth into the Northern and Southern hemispheres. It is an imaginary line located at 0 degrees latitude, halfway between the North and South poles. The term can als ...
, and fossil traces of land-based life forms survive from this period. These include fossilised trees from Kiltorcan,
County Kilkenny
County Kilkenny ( gle, Contae Chill Chainnigh) is a county in Ireland. It is in the province of Leinster and is part of the South-East Region. It is named after the city of Kilkenny. Kilkenny County Council is the local authority for the cou ...
, widespread bony fish and
freshwater mussel
Freshwater bivalves are one kind of freshwater mollusc, along with freshwater snails. They are bivalves that live in fresh water as opposed to salt water, which is the main habitat type for bivalves.
The majority of species of bivalve molluscs ...
fossils and the footprints of a four-footed
amphibian
Amphibians are tetrapod, four-limbed and ectothermic vertebrates of the Class (biology), class Amphibia. All living amphibians belong to the group Lissamphibia. They inhabit a wide variety of habitats, with most species living within terres ...
preserved in
slate
Slate is a fine-grained, foliated, homogeneous metamorphic rock derived from an original shale-type sedimentary rock composed of clay or volcanic ash through low-grade regional metamorphism. It is the finest grained foliated metamorphic rock. ...
on
Valentia Island
Valentia Island () is one of Ireland's most westerly points. It lies off the Iveragh Peninsula in the southwest of County Kerry. It is linked to the mainland by the Maurice O'Neill Memorial Bridge at Portmagee. A car ferry also departs from R ...
in
Munster
Munster ( gle, an Mhumhain or ) is one of the provinces of Ireland, in the south of Ireland. In early Ireland, the Kingdom of Munster was one of the kingdoms of Gaelic Ireland ruled by a "king of over-kings" ( ga, rí ruirech). Following the ...
.
Old Red Sandstone
The Old Red Sandstone is an assemblage of rocks in the North Atlantic region largely of Devonian age. It extends in the east across Great Britain, Ireland and Norway, and in the west along the northeastern seaboard of North America. It also exte ...
also formed at this time.
Between 400 million and 300 million years ago, parts of
Northwest Europe
Northwestern Europe, or Northwest Europe, is a loosely defined subregion of Europe, overlapping Northern and Western Europe. The region can be defined both geographically and ethnographically.
Geographic definitions
Geographically, Northw ...
, including much of Ireland, sank beneath a warm tropical sea. Great
coral reef
A coral reef is an underwater ecosystem characterized by reef-building corals. Reefs are formed of colonies of coral polyps held together by calcium carbonate. Most coral reefs are built from stony corals, whose polyps cluster in groups.
Co ...
s formed in these waters, eventually creating the
limestone
Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms whe ...
that still makes up about 65 per cent of the area of the island. As the waters receded,
tropical forest
Tropical forests (a.k.a. jungle) are forested landscapes in tropical regions: ''i.e.'' land areas approximately bounded by the tropic of Cancer and Capricorn, but possibly affected by other factors such as prevailing winds.
Some tropical fores ...
s and
swamp
A swamp is a forested wetland.Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. 497 p. Swamps are considered to be transition zones because both land and water play a role in ...
s flourished. The resulting vegetation eventually formed coal, most of which was later
eroded
Erosion is the action of surface processes (such as Surface runoff, water flow or wind) that removes soil, Rock (geology), rock, or dissolved material from one location on the Earth's crust#Crust, Earth's crust, and then sediment transport, tra ...
. This period, known as the
Carboniferous
The Carboniferous ( ) is a geologic period and system of the Paleozoic that spans 60 million years from the end of the Devonian Period million years ago ( Mya), to the beginning of the Permian Period, million years ago. The name ''Carbonifero ...
period, ended with further
tectonic movement
Plate tectonics (from the la, label=Late Latin, tectonicus, from the grc, τεκτονικός, lit=pertaining to building) is the generally accepted scientific theory that considers the Earth's lithosphere to comprise a number of large ...
which saw Ireland drift further northward. The resulting pressure created those Irish mountain and hill ranges that run in a northeast to southwest direction.
Mesozoic
![burren2](https://upload.wikimedia.org/wikipedia/commons/6/6f/Burren2.jpg)
By 250 million years ago, Ireland was at the latitude of present-day
Egypt
Egypt ( ar, مصر , ), officially the Arab Republic of Egypt, is a transcontinental country spanning the northeast corner of Africa and southwest corner of Asia via a land bridge formed by the Sinai Peninsula. It is bordered by the Mediter ...
and had a
desert climate
The desert climate or arid climate (in the Köppen climate classification ''BWh'' and ''BWk''), is a dry climate sub-type in which there is a severe excess of evaporation over precipitation. The typically bald, rocky, or sandy surfaces in desert ...
. It was at this time that most of the
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 dea ...
and
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) ...
were eroded. The thinner layers of limestone in the south of the country were also partially affected by this erosion. The limestone that was exposed by the disappearance of its sandstone mantle was subject to solution by weakly acidic water resulting in a
karst
Karst is a topography formed from the dissolution of soluble rocks such as limestone, dolomite, and gypsum. It is characterized by underground drainage systems with sinkholes and caves. It has also been documented for more weathering-resistant ro ...
ic landscape that can still be seen in
the Burren
The Burren (; ) is a karst/glaciokarst landscape centred in County Clare, on the west coast of Ireland.
Burren ...
in
County Clare
County Clare ( ga, Contae an Chláir) is a county in Ireland, in the Southern Region and the province of Munster, bordered on the west by the Atlantic Ocean. Clare County Council is the local authority. The county had a population of 118,817 ...
. Shortly after this period, organic debris in the seas around Ireland began to form the
natural gas
Natural gas (also called fossil gas or simply gas) is a naturally occurring mixture of gaseous hydrocarbons consisting primarily of methane in addition to various smaller amounts of other higher alkanes. Low levels of trace gases like carbo ...
and
petroleum
Petroleum, also known as crude oil, or simply oil, is a naturally occurring yellowish-black liquid mixture of mainly hydrocarbons, and is found in geological formations. The name ''petroleum'' covers both naturally occurring unprocessed crud ...
deposits that now play a role in the
economy of Ireland. Then, about 150 million years ago, Ireland was again submerged, this time in a chalky sea that resulted in the formation of
chalk
Chalk is a soft, white, porous, sedimentary carbonate rock. It is a form of limestone composed of the mineral calcite and originally formed deep under the sea by the compression of microscopic plankton that had settled to the sea floor. Chalk ...
over large parts of the surface. Traces of this survive under the
basalt
Basalt (; ) is an aphanite, 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 planetary surface, surface of a terrestrial ...
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 ...
that is found in parts of the north.
About 66 million years ago, the
volcanic
A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface.
On Earth, volcanoes are most often found where tectonic plates a ...
activity that formed this lava began. The
Mourne Mountains
The Mourne Mountains ( ; ga, Beanna Boirche), also called the Mournes or Mountains of Mourne, are a granite mountain range in County Down in the south-east of Northern Ireland. They include the highest mountains in Northern Ireland, the high ...
and other mountains in the northern part of the island formed as a result of this activity. Climatic conditions at this time were warm and vegetation thrived. Vegetable debris in the
Antrim Depression formed deposits of brown coal or
lignite
Lignite, often referred to as brown coal, is a soft, brown, combustible, sedimentary rock formed from naturally compressed peat. It has a carbon content around 25–35%, and is considered the lowest rank of coal due to its relatively low heat ...
which remain untouched down to the present time.
The warm conditions produced high rainfall that accelerated processes of erosion and the formation of karstic landscape forms.
Cenozoic
By 25 million years ago, Ireland was close to assuming its present position. From then on, a long period of erosion resulted in considerable
soil
Soil, also commonly referred to as earth or dirt, is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life. Some scientific definitions distinguish ''dirt'' from ''soil'' by restricting the former te ...
formation mantling most of the bedrock. In areas with good
drainage
Drainage is the natural or artificial removal of a surface's water and sub-surface water from an area with excess of water. The internal drainage of most agricultural soils is good enough to prevent severe waterlogging (anaerobic conditio ...
, the covering consisted of brown or grey soil, while in poorly drained areas, black
clay
Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4).
Clays develop plasticity when wet, due to a molecular film of water surrounding the clay par ...
tended to dominate. As the climate cooled, soil formation slowed, and a
flora
Flora is all the plant life present in a particular region or time, generally the naturally occurring (indigenous) native plants. Sometimes bacteria and fungi are also referred to as flora, as in the terms '' gut flora'' or '' skin flora''.
E ...
and fauna that would millions of years later be familiar to the first human inhabitants began to emerge. The present landscape of Ireland had more or less formed.
Before the Quaternary glaciations affected Ireland the landscape had a thick weathered
regolith
Regolith () is a blanket of unconsolidated, loose, heterogeneous superficial deposits covering solid rock. It includes dust, broken rocks, and other related materials and is present on Earth, the Moon, Mars, some asteroids, and other terrestria ...
on the uplands and
karst
Karst is a topography formed from the dissolution of soluble rocks such as limestone, dolomite, and gypsum. It is characterized by underground drainage systems with sinkholes and caves. It has also been documented for more weathering-resistant ro ...
in the lowlands. Pre-Quaternary relief was more dramatic than today's smoothed landforms.
Since about 1.7 million years ago, the Earth has been subjected to a cycle of warm and cold stages and these have, inevitably, affected Ireland. The earliest evidence we have for this effect comes from the period known as the
Ballylinian Warm Stage, some half a million years ago. At this time, most of what are now considered to be native Irish trees were already established on the island. The action of the ice during the cold stages was the major factor in bringing the Irish landscape to its current form.
Obvious impacts of the
ice
Ice is water frozen into a solid state, typically forming at or below temperatures of 0 degrees Celsius or Depending on the presence of impurities such as particles of soil or bubbles of air, it can appear transparent or a more or less opaq ...
on the landscape include the formation of
glacial valley
U-shaped valleys, also called trough valleys or glacial troughs, are formed by the process of glaciation. They are characteristic of mountain glaciation in particular. They have a characteristic U shape in cross-section, with steep, straight s ...
s such as
Glendalough
Glendalough (; ) is a glacial valley in County Wicklow, Ireland, renowned for an Early Medieval monastic settlement founded in the 6th century by St Kevin. From 1825 to 1957, the head of the Glendalough Valley was the site of a galena lead mine. ...
in Wicklow and of
corries, or glacial lakes. The depositing of mounds of debris under the melting ice created
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, a common feature of the landscape across the north midlands. Streams also formed under the ice and the material deposited by these formed
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 Amer ...
s (
Irish
Irish may refer to:
Common meanings
* Someone or something of, from, or related to:
** Ireland, an island situated off the north-western coast of continental Europe
***Éire, Irish language name for the isle
** Northern Ireland, a constituent unit ...
''eiscir''). The greatest of these, the
Esker Riada
The Esker Riada ( ga, Eiscir Riada) is a system of eskers that stretch across the middle of Ireland, between Dublin and Galway.
Geography
The Esker Riada is a collection of eskers that passes through the counties of Dublin, Meath, Kildare, Wes ...
, divides the northern and southern halves of the island and its ridge once served as the main highway connecting the east and west coasts. About one half of the coastline consists of a low-lying dune pasture land known as ''
machair
A machair (; sometimes machar in English) is a fertile low-lying grassy plain found on part of the northwest coastlines of Ireland and Scotland, in particular the Outer Hebrides. The best examples are found on North and South Uist, Harris an ...
''.
Rocks and soil types
![Ireland-CliffsofMoher](https://upload.wikimedia.org/wikipedia/commons/e/e8/Ireland-CliffsofMoher.jpg)
The large central lowland is of
limestone
Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms whe ...
covered with glacial deposits of clay and sand, with widespread
bogs and lakes. The
Bog of Allen is one of the largest bogs. The coastal mountains vary greatly in geological structure. In the south, the mountains are composed of
Old Red Sandstone
The Old Red Sandstone is an assemblage of rocks in the North Atlantic region largely of Devonian age. It extends in the east across Great Britain, Ireland and Norway, and in the west along the northeastern seaboard of North America. It also exte ...
with limestone river valleys. Around the
Ulster
Ulster (; ga, Ulaidh or ''Cúige Uladh'' ; sco, label= Ulster Scots, Ulstèr or ''Ulster'') is one of the four traditional Irish provinces. It is made up of nine counties: six of these constitute Northern Ireland (a part of the United King ...
/
Connacht
Connacht ( ; ga, Connachta or ), is one of the provinces of Ireland, in the west of Ireland. Until the ninth century it consisted of several independent major Gaelic kingdoms (Uí Fiachrach, Uí Briúin, Uí Maine, Conmhaícne, and Delbhn ...
border, the mountains are made from
Carboniferous
The Carboniferous ( ) is a geologic period and system of the Paleozoic that spans 60 million years from the end of the Devonian Period million years ago ( Mya), to the beginning of the Permian Period, million years ago. The name ''Carbonifero ...
sandstones with softer Carboniferous limestones below them. In central Ulster, the mountains are predominantly made from metamorphic rocks. In the west of both Connacht and Ulster, the mountains are mostly metamorphic rocks with some granite. The
Mourne and
Wicklow Mountains
The Wicklow Mountains (, archaic: ''Cualu'') form the largest continuous upland area in the Republic of Ireland. They occupy the whole centre of County Wicklow and stretch outside its borders into the counties of Dublin, Wexford and Carlow. Wh ...
are mainly
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 undergro ...
. Much of the northeast of Ireland is a
basalt
Basalt (; ) is an aphanite, 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 planetary surface, surface of a terrestrial ...
plateau. An area of particular note is the
Giant's Causeway
The Giant's Causeway is an area of about 40,000 interlocking basalt columns, the result of an ancient volcanic fissure eruption. It is located in County Antrim on the north coast of Northern Ireland, about three miles (5 km) northeast of ...
on the north coast, a mainly basalt formation caused by volcanic activity between 50 and 60 million years ago. The basalts were originally part of the great
Thulean Plateau
The North Atlantic Igneous Province (NAIP) is a large igneous province in the North Atlantic, centered on Iceland. In the Paleogene, the province formed the Thulean Plateau, a large basaltic lava plain, which extended over at least in area and ...
formed during the
Paleogene
The Paleogene ( ; British English, also spelled Palaeogene or Palæogene; informally Lower Tertiary or Early Tertiary) is a geologic period, geologic period and system that spans 43 million years from the end of the Cretaceous Period million yea ...
period.
The soils of the north and west tend to be poorly drained
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 efficien ...
s and
gleys, including peaty
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 hum ...
s. In contrast, in the south and east the soils are free-draining brown earths and brown and grey-brown podzols.
An unusual environment is present in north Clare, in
the Burren
The Burren (; ) is a karst/glaciokarst landscape centred in County Clare, on the west coast of Ireland.
Burren ...
. This
karst
Karst is a topography formed from the dissolution of soluble rocks such as limestone, dolomite, and gypsum. It is characterized by underground drainage systems with sinkholes and caves. It has also been documented for more weathering-resistant ro ...
landscape consists of limestone
bedrock
In geology, bedrock is solid Rock (geology), rock that lies under loose material (regolith) within the crust (geology), crust of Earth or another terrestrial planet.
Definition
Bedrock is the solid rock that underlies looser surface mater ...
, with little or no soil in the innermost areas. There are numerous
sinkhole
A sinkhole is a depression or hole in the ground caused by some form of collapse of the surface layer. The term is sometimes used to refer to doline, enclosed depressions that are locally also known as ''vrtače'' and shakeholes, and to openi ...
s, where surface water disappears through the
porous
Porosity or void fraction is a measure of the void (i.e. "empty") spaces in a material, and is a fraction of the volume of voids over the total volume, between 0 and 1, or as a percentage between 0% and 100%. Strictly speaking, some tests measure ...
rock surface, and extensive cave systems have been formed in some areas.
Doolin Cave is the site of one of the world's longest known free-hanging
stalactite
A stalactite (, ; from the Greek 'stalaktos' ('dripping') via
''stalassein'' ('to drip') is a mineral formation that hangs from the ceiling of caves, hot springs, or man-made structures such as bridges and mines. Any material that is soluble an ...
s.
References
External links
Geological Survey Maps Collection Irish Virtual Research Library and Archive, University College Dublin
{{Geology of Europe