The river pothole

Hywel Griffiths

Grain by grain,
the presence of
absence
grows
around the slow-wound
depths of cylinders;
abrasion’s eraser
dances, grinds
against the ground,
carving in bare
river beds
pieces of negative space,
slowly,
ever so slowly
etching a line
in the land,
a line etched
by millennia,
a loss
through
coalescence.

The Science

Potholes - cylindrical or hemispherical holes formed by erosion in bedrock rivers - are one of the principal ways in which rivers erode landscapes. Once initiated as small depressions on rock surfaces, potholes can deepen and widen owing to abrasion by sediment. Over time, if they continue to erode, and are not destroyed by faster erosion on surrounding bedrock, neighbouring potholes can coalesce, creating inner channels which can draw water away from older channels at higher elevations. This process is typically very slow - imperceptible over human lifetimes - but creates some of the most striking and beautiful river scenery.

The Poet

Hywel Griffiths is a Senior Lecturer in Physical Geography in the Department of Geography and Earth Sciences, Aberystwyth University, Wales. He is a fluvial geomorphologist and poet, writing mainly in the Welsh strict meter form of cynghanedd, based on alliteration and internal rhyme, elements of which can be seen in this poem. His English-language poetry has been published in Geohumanities, Cultural Geographies and Poetry Wales and he is the author of three Welsh-language volumes. He is currently co-authoring a book on river potholes, incorporating science and the arts. For more information visit hywelgriffiths.cymru or follow him on Twitter @HywelGriffiths.

Next poem: 4 seconds of history by Manan Bhan