Get Involved
Help us sustain our lough, wildlife & community
Send us a photo
Share your photos

Fire and Ice

Fire
500 million years ago, what is now County Down, was covered by a deep, tropical ocean. Fine ‘silts’ –mudlike particles, fell onto the ocean sea bed. At times coarser grit washed to the coast from the rivers and slid over the fine silts. This was repeated for over 100 million years (through periods known as the ‘Ordovician’ and ‘Silurian’).

Over time these layers hardened into rock known as ‘greywackes’, fine shales and mudstones. Then, as the continental plates of the earth’s crusts shifted there was a period (known as the Caledonian) of massive upheavels and volcanic activity. Under great pressure and the heat the rocks were compressed and folded and in places the shales and mudstones where changed (metamorphosed) into slate. As the rock folded and fractured it was forced up to the surface and can now be seen all these years later in the almost vertical jagged rocks that catch the eye around Strangford Lough at Killard point, Kilclief, Ballyquinton Point, Kearney Point.  

Ice
This sea inlet emerged from under the melting ice-sheets of the Ice Age and is for the most part less than 10m in depth.

The retreating ice left behind the very distinctive hills called drumlins that stretch from this area across to the west of Ireland. The Lough's islands are a drowned drumlin field. 

There is a deeper Y-shaped channel (possibly an old river-valley or geological fault-line) up to 66 m deep which extends from the Narrows up the central portion of the Lough. The underlying rock is largely Silurian. 
  • The surface of the bed and the indented shore of the Lough ranges from bedrock in areas with strong currents to fine mud in sheltered waters. The west shore has numerous islands typical of flooded drumlin topography.
  • The Lough contains extensive areas of mudflat and also sandflats (mainly at the northern end), with gravel, cobble, boulder and rocky shores as one moves further south. It also has areas of saltmarsh, the most extensive being in the Comber river estuary.
  • The water in the Lough is virtually fully saline except at the mouths of the two moderate-sized rivers, the Comber and the Quoile, and where several streams drain into it from the catchment of about 900 km² where it may be somewhat brackish.
  • The area has a mild climate with relatively low rainfall compared with other areas of Ireland, infrequent frosts and prevailing west to southwest winds.
  • The Lough has a huge variety of subtidal and intertidal habitats with over 2,000 recorded species. It is important for marine invertebrates, algae and saltmarsh plants, for wintering and breeding wetland birds, and for marine mammals.
For further information on this area please see related publications - Strangford Lough The Wildlife of an Irish Sea Lough by Robert Brown, Chapter 2, How the Lough was Made.
Mail Print
Related Publications
View All Publications