Glenmacnass Waterfall () is an 80-metre high waterfall situated at the head of the Glenmacnass Valley in the

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 ...

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 ...

. The Glenmacnass Waterfall is a popular tourist destination and scenic viewpoint area in the Wicklow Mountains. The Waterfall is bounded to the west by

Tonelagee Tonelagee () at , is the 25th–highest peak in Ireland on the Arderin scale, and the 33rd–highest peak on the Vandeleur-Lynam scale.Mountainviews, (September 2013), "A Guide to Ireland's Mountain Summits: The Vandeleur-Lynams & the Arderins ...

, and to the east by

Scarr Scarr Mountain at , is the 174th–highest peak in Ireland on the Arderin scale, and the 207th–highest peak on the Vandeleur-Lynam scale.Mountainviews, (September 2013), "A Guide to Ireland's Mountain Summits: The Vandeleur-Lynams & the Arde ...

mountain. The entire Glenmacnass Valley can be accessed by the R115 road (also called the ''Military Road''), which connects the

Sally Gap The R759 road is a regional road in Ireland running south-east to north-west through the Sally Gap in the Wicklow Mountains, from the R755 near Roundwood in East Wicklow to the N81 in West Wicklow. The other route through the Wicklow Mounta ...

in the north, to the village of Laragh in the south.

Geography

The Glenmacnass River begins high up on the southeast slopes of

Mullaghcleevaun Mullaghcleevaun () at , is the 15th–highest peak in Ireland on the Arderin scale, and the 20th–highest peak on the Vandeleur-Lynam scale.Mountainviews, (September 2013), "A Guide to Ireland's Mountain Summits: The Vandeleur-Lynams & the Ar ...

, with smaller tributaries flowing in from the eastern slopes of

; the river then reaches the top of the waterfall at an elevation of above sea-level, where it falls down the waterfall in 3 staggered drops to an elevation of above sea-level, where it reaches the Glenmacnass Valley floor. The river continues through the

U-shaped Many shapes have metaphorical names, i.e., their names are metaphors: these shapes are named after a most common object that has it. For example, "U-shape" is a shape that resembles the letter U, a bell-shaped curve has the shape of the vertical ...

valley until it joins the Avonmore River () at the village of Laragh. It is later joined by the Avonbeg () to become the Avoca and eventually flows into the

Irish Sea The Irish Sea or , gv, Y Keayn Yernagh, sco, Erse Sie, gd, Muir Èireann , Ulster-Scots: ''Airish Sea'', cy, Môr Iwerddon . is an extensive body of water that separates the islands of Ireland and Great Britain. It is linked to the Ce ...

at the coastal town called

Arklow Arklow (; ; , ) is a town in County Wicklow on the southeast coast of Ireland. The town is overlooked by Ballymoyle Hill. It was founded by the Vikings in the ninth century. Arklow was the site of one of the bloodiest battles of the 1798 re ...

Geology

Geological Survey of Ireland Geological Survey Ireland or Geological Survey of IrelandS.I. No. 300/2002 - Communications, Energy and Geological Survey of Ireland (Transfer of Departmental Administration and Ministerial Functions) Order 2002 ( ga, Suirbhéireacht Gheolaíochta ...

(GSI) regard the valley as a "stunning example of a glaciated U-shaped valley, with oversteepened cliff sides and a flat floor". The valley dates from the last

glacial period 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 ...

called the

quaternary glaciation The Quaternary glaciation, also known as the Pleistocene glaciation, is an alternating series of glacial and interglacial periods during the Quaternary period that began 2.58 Ma (million years ago) and is ongoing. Although geologists describe ...

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 ...

, and contains

moraines A moraine is any accumulation of unconsolidated debris (regolith and rock), sometimes referred to as glacial till, that occurs in both currently and formerly glaciated regions, and that has been previously carried along by a glacier or ice shee ...

marking the positions of the ice-front as it retreated back towards the source area higher up in the centre of the Wicklow mountains. The GSI highlight an impressive moraine about halfway between the waterfall and Laragh and can be seen as a boulder-strewn mound running right across the valley. Glenmacnass Waterfall flows over grey-colored, smooth

porphyritic Porphyritic is an adjective used in geology to describe igneous rocks with a distinct difference in the size of mineral crystals, with the larger crystals known as phenocrysts. Both extrusive and intrusive rocks can be porphyritic, meaning all ...

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 ...

bedrock (part of the

Lugnaquilla LugnaquillaLugnaquilla
.

pluton In geology, an igneous intrusion (or intrusive body or simply intrusion) is a body of intrusive igneous rock that forms by crystallization of magma slowly cooling below the surface of the Earth. Intrusions have a wide variety of forms and com ...

, which is itself from the late-Caledonian (405 Ma) Leinster Granite

Batholith A batholith () is a large mass of intrusive igneous rock (also called plutonic rock), larger than in area, that forms from cooled magma deep in Earth's crust. Batholiths are almost always made mostly of felsic or intermediate rock types, such ...

Formation). Further down the valley, on each side of the waterfall, dark grey-to-black, jagged

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 o ...

rock (part of the Lower

Palaeozoic 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 '' ...

Maulin Formation) can be seen jutting out; thus the waterfall has formed at the boundary between these two major rock types.

Access

The Glenmacnass Waterfall is a popular tourist destination and scenic viewpoint area in the Wicklow Mountains, and the entire Glenmacnass Valley can be accessed by the R115 road (also called the ''Military Road''), which connects the

to Laragh. There are parking facilities at the top of the waterfall, and the waterfall and valley are in the

Wicklow Mountains National Park Wicklow Mountains National Park () is a protected area in Ireland, one of six national parks in the country. The park stretches through County Wicklow as well as small areas of South Dublin and Dún Laoghaire–Rathdown in County Dublin. Th ...

Gallery

File:Misty Glenmacnass.jpg, Mist on the waterfall File:Glenmacnass waterfall from the south - geograph.org.uk - 64540.jpg, From south File:Glenmacnass Waterfall, Wicklow.jpg, Heavy flow File:Glenmacnass Waterfall - geograph.org.uk - 19567.jpg, From ''Military Road'' File:Glenmacnass - geograph.org.uk - 627290.jpg, Glenmacnass valley File:Glenmacnass River Wicklow Way.jpg, Glenmacnass River above Laragh

References

External links