Physical Processes (Leaving Cert Geography): Revision Notes

Physical Processes

The physical geography of the West of Ireland has been shaped by several natural processes that have created the distinctive landscape we see today. This peripheral region displays unique characteristics in its relief, drainage, soils, vegetation and climate patterns.

Relief

The landscape of the West has been formed through three major geological processes that worked together over millions of years to create the current terrain.

Folding

The western section of the region features dramatic upland areas, while the eastern parts are characterised by lower-lying terrain. The mountainous western coastline was created during an ancient period of geological activity.

Over time, weathering and erosion have worn down these ancient mountains to their present height. Notable examples include the Twelve Pins and Maumturk Mountains in Connemara, County Galway, and Croagh Patrick in County Mayo. These fold mountains represent some of Ireland's most challenging and spectacular terrain.

Glaciation

During the most recent ice age, the Pleistocene period, glacial activity dramatically reshaped the mountainous areas of the West. As glaciers moved downslope, they carved out distinctive landscape features through powerful erosive processes.

The glacial activity created cirques and deep valleys that characterise much of the upland areas today. When the ice age ended, these glaciers left behind significant deposits that continue to influence the region's geography.

The eastern portion of the region forms part of the Irish Central Plain, where underlying limestone bedrock lies beneath these glacial deposits. In areas like Clew Bay in County Mayo, glacial movement shaped boulder clay into distinctive landscape features.

The post-glacial rise in sea levels flooded many former glacial and river valleys, creating features like the fiord at Killary Harbour in County Mayo.

Coastal processes

The Atlantic Ocean's powerful influence has significantly shaped the western coastline through continuous erosion and deposition processes. The prevailing Atlantic weather systems approach from the southwest, giving coastal features a distinctive directional pattern.

Coastal erosion has created numerous headlands and dramatic cliffs, while areas of deposition have formed beaches and sheltered bays. This ongoing interaction between land and sea continues to modify the coastline, with most cliffs and bays showing a south-westerly orientation due to the direction of the prevailing winds and wave action.

Drainage

The region contains several significant river systems and lakes, though drainage quality varies considerably across different areas.

Major rivers and lakes

The main river systems include:

• River Moy in County Mayo
• River Corrib in County Galway
• River Clare in County Galway
• River Suck in County Roscommon
• River Shannon, which flows along the eastern boundary

Important lakes in the region are:

• Lough Corrib in County Galway
• Lough Mask in County Mayo
• Lough Conn in County Mayo

Drainage problems

Much of the West suffers from poor drainage conditions that create ongoing challenges for land use. The impermeable boulder clay covering large areas prevents effective water drainage, leading to frequent waterlogging.

The River Shannon demonstrates typical drainage issues found throughout the region. Its gentle profile means water flows very slowly, causing regular flooding of surrounding areas. Evidence of poor drainage can be seen in the numerous lakes along the river's course, including Lough Allen and Lough Ree.

Drumlin formations further complicate drainage patterns by forcing streams to flow around them, creating deranged drainage systems where water channels change direction repeatedly rather than following straight paths to the sea.

Soil

Soil quality varies throughout the West, influenced by local relief, drainage conditions and climate patterns. However, soils are generally of poor quality, limiting agricultural potential across much of the region.

Peat soils

Extensive areas of upland terrain in Mayo and Galway are covered by peat soils that form shallow blanket bogs. These soils develop in waterlogged conditions where organic matter accumulates faster than it can decompose.

The poor mineral content and inaccessibility of blanket bogs makes them unsuitable for mechanised agriculture. In areas with particularly poor drainage, deeper raised bogs have developed in former lake beds and natural hollows.

Podzols

Heavy rainfall combined with naturally acidic conditions creates podzol soils across much of the region. These soils form through a process where minerals are washed downward through the soil layers.

As minerals accumulate in lower soil layers, they create an impermeable barrier called a hardpan between different soil horizons. This hardpan prevents effective drainage, leading to waterlogging that persists throughout the year, particularly during winter months.

Gleys

Gley soils develop where clay deposits and drumlin formations create poorly drained conditions. In these waterlogged environments, soil becomes severely saturated and loses its oxygen content.

When water fills all the soil pores and removes oxygen, very little vegetation can survive these conditions. However, rushes have adapted to thrive in gley soils, making these areas suitable primarily for rough grazing of livestock rather than intensive agriculture.

Brown earths

Although brown earths make up 64% of all Irish soils, they occupy only limited areas within the West region, mainly in parts of south Galway and other low-lying locations.

In the West, these soils tend to be shallow rather than the deeper brown earths found elsewhere in Ireland. They developed from the humus created by deciduous forests that originally covered the lowland areas.

Brown earths in this region are normally fertile and well-drained, making them valuable for agricultural use. However, year-round rainfall causes some leaching, making the soils slightly acidic and less suitable for certain crops compared to brown earths in drier regions.

Vegetation

Natural vegetation patterns across the West depend heavily on soil types and local drainage conditions. The challenging environmental conditions support distinctive plant communities adapted to wet, acidic conditions.

Bog cotton, heather and scrub grasses dominate the blanket bogs found in mountainous regions. Rough grassland grows on podzolic and gley soils, with rushes frequently becoming the dominant vegetation type.

Brown earths originally supported thick deciduous grasslands before human settlement, but these areas are now primarily used for agricultural grassland production where drainage permits.

Climate

The West experiences a cool temperate oceanic climate similar to the rest of Ireland, but with some distinctive regional characteristics due to its Atlantic coastal location.

Precipitation

Precipitation levels in the West exceed those found anywhere else in Ireland. Several factors combine to create these high rainfall totals.

Ireland's position places it at the meeting point of warm south-westerly air masses and cold polar air masses. This creates cyclonic weather systems that move inland from the Atlantic, bringing heavy rainfall.

The prevailing south-westerly winds absorb moisture from warm ocean currents as they blow towards Ireland. When these warm air masses encounter the mountain ranges of the western coastline, they are forced to rise upward. As the air rises and cools, it condenses into rain clouds, producing heavy precipitation.

Upland regions receive over $2,500\text{mm}$ of precipitation annually, while lowland areas still receive over $1,100\text{mm}$ per year. This greatly exceeds the $800\text{mm}$ average for eastern Ireland. Most precipitation falls as rain, with snowfall rarely occurring except on mountain peaks during winter and early spring.

Temperatures

The West maintains a small temperature range regulated by the moderating influence of the Atlantic Ocean. Winters are mild, with average temperatures around $6°\text{C}$, while summers remain relatively cool at $15°\text{C}$, giving an annual temperature range of just $9°\text{C}$.

Several factors influence regional temperature patterns:

The North Atlantic Drift, a warm ocean current, increases air temperatures during winter months. This current prevents extreme cold conditions and keeps the coastline ice-free even when other countries at similar latitudes experience harsh winter weather.

Prevailing south-westerly winds help moderate temperatures year-round, keeping conditions mild during winter and drawing cooling effects from the North Atlantic Drift during summer.

Altitude significantly affects local temperatures, making mountainous regions much colder than low-lying areas. Upland regions are also more exposed to winds, creating additional cooling effects known as wind chill.