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When rainfall is very heavy or extended for a long period, rivers, and groundwater systems in karst areas such as the Gort-Kinvara Lowlands, may not be able to absorb all the extra water. This is when flooding occurs. Unfortunately whilst our predecessors avoided building on river floodplains, pressure for houses has led to reductions in floodplain areas and hence increased flood risk in some locations. Geological data can be essential in analysing the problem and proposing solutions.

Railway flooded
Railway flooded. Photo: Conor MacDermot


Much of the Earth's surface is covered by unconsolidated sediments which can be especially prone to instability. Water often plays a key role in lubricating the slope failure. Instability is often significantly increased by Man's activities in building houses, roads, drainage and agricultural changes. Landslides, mud flows, bog bursts (in Ireland) and debris flows are the result. Bedrock is generally more stable, but rockfalls are a real danger too. Only a geologist will be able to assess the whole problem and help avoid serious loss of life.

Landslides are more common in unconsolidated material than in bedrock, and where the sea constantly erodes the material at the base of a cliff (e.g. near Greystones, Co. Wicklow,) landslides and falls lead to recession of the cliffs.

Landslip near Greystones, Co. Wicklow.
Landslip near Greystones, Co. Wicklow. Photo: Matthew Parkes

For more information about landslides, including the 2003 Pollatomish Landslide in Co. Mayo, Click here.


Mining out coal or minerals leads to rapid creation of underground spaces. Whilst these are made safe for miners during the work, if left alone, they can later collapse and cause subsidence at the surface as the mass of rock adjusts. In modern mines [Tara, Lisheen and Galmoy] all underground spaces are backfilled with waste rock, which prevents the risk, but in older mining districts subsidence may still occur. Geologists can monitor and predict the likelihood depending on the rock type.

Aerial view of Tennant mine collapse in 1990.
Aerial view of Tennant Salt Mine collapse 1990
Photo: Geological Survey of Northern Ireland
and Department of Enterprise, Trade and Investment
Hazards not common to Ireland
See the
Earthquakes , Volcanoes  and Tsunami pages.

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