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 Ireland. They occupy the whole centre of County Wicklow and stretch outside its borders into the counties of Dublin, Wexford and Carlow. Where the mountai ...

Ireland Ireland (, ; ; Ulster Scots dialect, Ulster-Scots: ) is an island in the North Atlantic Ocean, in Northwestern Europe. Geopolitically, the island is divided between the Republic of Ireland (officially Names of the Irish state, named Irelan ...

. 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 (), is 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 Arder ...

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

Sally Gap Sally or Sallie may refer to: People and characters Persons * Sally (name), a female given name, and list of notable people with the name; a diminutive of Sarah. * , French influencer and activist * Axis Sally, the name given to female radio pr ...

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 Ard ...

, 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 shape A shape is a graphics, graphical representation of an object's form or its external boundary, outline, or external Surface (mathematics), surface. It is distinc ...

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 is a body of water that separates the islands of Ireland and Great Britain. It is linked to the Celtic Sea in the south by St George's Channel and to the Inner Seas off the West Coast of Scotland in the north by the North Ch ...

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 Battle of Arklow, bloodiest battles ...

Geology

Geological Survey of Ireland Geological Survey Ireland or Geological Survey of Ireland (), founded in 1845, is the National Earth Science agency of Ireland. Overview Geological Survey Ireland is a division of the Department of Communications, Climate Action and Environment a ...

(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 period, glacial and interglacial, interglacial periods during the Quaternary period that began 2.58 Year#SI prefix multipliers, Ma (million ...

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 g ...

, 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 sh ...

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 ...

granite Granite ( ) is a coarse-grained (phanerite, phaneritic) intrusive rock, 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 coo ...

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 rock, intrusive igneous rock (also called plutonic rock), larger than in area, that forms from cooled magma deep in the Earth's crust. Batholiths are almost always made mostly of felsic or intermediate ...

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

schist Schist ( ) is a medium-grained metamorphic rock generally derived from fine-grained sedimentary rock, like shale. It shows pronounced ''schistosity'' (named for the rock). This means that the rock is composed of mineral grains easily seen with a l ...

rock (part of the Lower

Palaeozoic The Paleozoic ( , , ; or Palaeozoic) Era is the first of three geological eras of the Phanerozoic Eon. Beginning 538.8 million years ago (Ma), it succeeds the Neoproterozoic (the last era of the Proterozoic Eon) and ends 251.9 Ma at the start of ...

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.

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 File:Glenmacnass Waterfall in 1974 or 1975.jpg, Young people visiting the waterfall in the 1970s

References

External links