In Awe of Drumlins

Drumlins to the right of me, drumlins to the left of me.  Everywhere I look there are drumlins. I live and work on a drumlin in a land of drumlins.  What are drumlins?  They are small ridge shaped hills and its not surprising that  the name originates from the Gaelic "droimnin" meaning little ridge. They cover a large swathe of Ireland mainly found north of a line from Mayo in the west to Louth in the east.  In this part of Ireland, (Mayo) they occur in swarms, predominately but not entirely with the ridge axis running roughly east to west.  Further afield they can be found in North America, Northern Europe and also in the southern hemisphere.


No bedrock is to be found in a drumlin because they are composed of deposits of loose material, rocks, clay, silt sometimes with a discernable layering.  In other words they are gigantic earthworks which can reach up to 150 feet in height and can stretch for  a mile or so along the axis of the ridge.  They are higher at one end than the other. In this area they are higher at the eastern end of the ridge axis and tend to taper off towards the western end.


What caused the drumlins?  They emerged as landforms at the end of the last ice age around 16 thousand years ago. They are a legacy of different climate and a testimony to the dynamic impact of climate change.  The material in the drumlin does not reflect the composition of the bedrock on which they stand.  In other words the material has been transported from somewhere else and dropped.  Its been scooped, gauged, scraped  and then carried  in the heart of a glacier and abandoned at a new place.  A single boulder carried and left by a glacier in this manner is known as an erratic; drumlins could be called erratic hills.  If  these hills reach a height of 150 feet then what was the size of the monster that made them?  Evidence suggests that in this area that monster was an outlet glacier to the Atlantic ocean from the Irish ice sheet which was part of the British/Scandinavian ice sheet.  Perhaps up to 2000 feet high with only the tops of the highest local mountains peeking out, this glacier flowed out to sea through the area now known as Clew Bay. As the sea level rose as the ice age ended some of the drumlins in the bay  became  cut off from the mainland to form its many islands.  Still others remained attached to the mainland as long promontories reflecting their east/west axis.


I think the process was wondrous and awesome.  It provides me daily with a reminder of climate change - in this case purely natural.  Now human beings are now promulgating the most profound and dangerous climate change yet.  By dumping more CO2 in the atmosphere than there has been for more than 3 million years in just the span of the past couple of centuries we have put an enormous spanner in the works.


I am full of awe for the climate change of the past and full of fear for climate change of the future.

Drowned drumlins of Clew Bay from Crough Patrick mountain

One of the Clew Bay Drumlins