Physical Processes (Leaving Cert Geography): Revision Notes

Physical Processes

The Greater Dublin Area (GDA) is shaped by three main physical factors that work together to create its distinctive geographical characteristics. Understanding these physical processes helps explain why this region differs significantly from other parts of Ireland, particularly the western regions.

Relief and drainage

The landscape of the Greater Dublin Area is predominantly characterised by gently rolling lowland terrain. This undulating lowland relief forms the foundation of the region's physical geography and influences many other geographical processes.

Mountain formations

The main exceptions to this lowland pattern are the Dublin and Wicklow Mountains, located to the south of the region. These upland areas were created during the Caledonian folding period, approximately 400 million years ago. The mountains serve an important function by providing shelter to the southern parts of the region.

The mountainous terrain consists largely of resistant metamorphic rock, which creates distinctive landscape features. For example, Wicklow Head demonstrates how this hard rock forms prominent headlands along the coast. In contrast, areas of softer rock along the lowland coast experience more deposition, creating features such as the beaches at Portmarnock.

Drainage characteristics

The region benefits from excellent natural drainage systems. This occurs because limestone serves as the main bedrock throughout much of the area. The permeable nature of limestone allows water to drain efficiently through the soil, preventing waterlogging during the wetter months of the year.

Several major rivers, including the Liffey, Tolka, Vartry and Boyne, flow through the region before reaching the Irish Sea. These waterways not only provide drainage but also contribute to soil fertility through the deposition of sediments.

Coastal processes

Unlike Ireland's western coastline, the Greater Dublin Area experiences less severe coastal erosion and weathering. The Irish Sea provides some shelter from the most powerful Atlantic currents, meaning that coastal processes operate with reduced intensity compared to the exposed western shores.

Climate

The Greater Dublin Area experiences a cool temperate oceanic climate, similar to the rest of Ireland. However, several factors combine to create subtle but important differences from other regions, particularly those in the west.

Temperature patterns

The region enjoys slightly more sunshine than western areas, receiving approximately four hours per day compared to just 2.3 hours in western regions. Winter temperatures average around 5°C, which is marginally colder than western Ireland's winter averages. Summer temperatures reach an average of 16°C in July, making them slightly warmer than western regions.

These temperature differences result from the region's distance from the moderating effect of the Atlantic Ocean. During winter months, the Atlantic Ocean loses heat slowly, creating a warming effect on areas close to the western coast. The Greater Dublin Area lies too far inland to benefit significantly from this effect, while the Irish Sea is too small to provide substantial temperature moderation.

Precipitation patterns

Annual precipitation in the Greater Dublin Area averages 750mm, which represents less than half the rainfall received by western regions (1500-2500mm annually). This significant difference results from the region's position relative to Ireland's dominant weather patterns.

The rain-shadow effect plays a crucial role in creating these drier conditions. As moisture-laden air masses move inland from the Atlantic, they encounter the mountains of western Ireland. The air rises, cools, and deposits most of its moisture on the western slopes. By the time these air masses reach the Greater Dublin Area, they contain much less moisture.

The Dublin and Wicklow Mountains contribute to this effect by reducing the impact of Ireland's prevailing south-westerly winds. These mountains receive higher levels of relief rainfall, which further reduces precipitation in the surrounding lowland areas.

Soil

The soils of the Greater Dublin Area are generally fertile and well-suited to agricultural activities. This fertility results from the region's unique combination of climate, relief, and historical vegetation patterns.

Soil formation

The region's soils developed beneath extensive deciduous forests that once covered the landscape. As these trees shed their leaves each autumn and winter, the organic matter accumulated on the forest floor and gradually decomposed to form humus. Over thousands of years, this process created the brown earth soils that characterise much of the area today.

Soil characteristics and distribution

The region's major rivers have contributed additional fertility through the deposition of alluvial materials. Areas such as the Boyne Valley in County Meath represent some of Ireland's most productive agricultural land due to these river-deposited sediments.

Marine deposition has created distinctive light, sandy soils along the North County Dublin coastline. These soils combine good drainage with reasonable fertility, making them particularly suitable for market gardening and horticulture.

The underlying limestone bedrock in parts of County Meath and County Kildare contributes to unusually high calcium content in the brown earth soils of these areas. This characteristic enhances soil fertility and supports intensive agricultural production.

Mountain soils

Along the slopes of the Dublin and Wicklow Mountains, different soil conditions prevail. Here, infertile peat soils have developed due to the combination of higher altitude, increased precipitation, and cooler temperatures. These conditions slow decomposition processes and lead to the accumulation of organic matter in waterlogged conditions.