by Vincent Roche, UCD

Old fractures, new heat

Unlocking the subsurface for the energy transition in the Dublin Basin

January 2026

Friday, 22nd December: Under blue skies and enjoying unexpectedly pleasant weather conditions, Simon Vokes, a PhD student at University College Dublin, and I, Dr Vincent Roche, Assistant Professor in Structural Geology at UCD, carried out low-tide fieldwork along the coastal outcrops near Rush, County Dublin.

The work forms part of a broader field campaign led by the UCD GEMINI team, which began a few months ago. The aim of this campaign is to characterize fracture systems across the Dublin region, using data collected from quarries and coastal outcrops. 

what is a fracture?

A fracture is any break or structural discontinuity in rock in which two rock fracture surfaces (usually planar) are separate. Fractures range in scale from microscopic cracks to kilometre-wide zones.

These fractures, inherited from past tectonic deformation millions of years ago, play a fundamental role in the development of deep geothermal energy systems in the Dublin area. In carbonate rocks such as limestone, widely present beneath the city, the ability of these hot/warm fluids to circulate is largely controlled by fracture networks - interconnected cracks in the rock layers. These networks act as preferential pathways for fluid flow that enable geothermal energy to be collected at depth and used for heating.

During our fieldwork, Simon measured key fracture parameters including length, orientation and frequency. When combined with data collected across the wider Dublin area, these measurements help to build a 3D picture of subsurface fracture networks. Such insights are crucial for predicting permeability (and therefore how easy it is to move and replenish the heat from below ground) in locations identified as potential sites for deep geothermal reservoirs, such as the Grangegorman site.

By linking surface observations with subsurface models, this research contributes to a better understanding of Dublin’s geothermal potential.

Images: Simon Vokes makes notes on the rocky shore near Rush, County Dublin; inset: Dr Vincent Roche.

UCD is a GEMINI partner.