The omens and warnings of Anything Can Happen and In Iowa ensure that the mere mention of natural phenomena in decline awakens fear of global threat. The first-person speaker recounts a personal experience flying above the massive glacier behind the town of Hōfn in south-east Iceland.

Heaney toured Iceland in 2004 with piper  Liam O’Flynn on a joint poetry/ music venture; en route to their next destination Heaney overflew ‘ this stony grey scar of ice …we learned that the ice is actually melting. As a ‘child of earth’ I’ve rarely felt more exposed’ (DOD p.411)

Heaney writes his headline: an ice mass of huge magnitude is thawing: The three-tongued glacier has begun to melt.

 The Icelanders foresee a bleak scenario as things warm up – boulder milt (very possibly a porte-manteau combination of ‘melt’ and ‘silt’) – liquid momentum sending geological debris seawards (wallowing across the delta flats) and age-old miles-deep shag-ice shifting.

Seen from a plane the moving (undead) glacier appears as he might have expected: irregular projecting surfaces laid on rock ridged and rock-set, flour coloured (grey-gristed), with animal skin textures (earth-pelt), its nap resulting from the age-old inter-grinding of ice and rock (aeon scruff).

He felt the glacier’s hostility (feared its coldness), its low temperatures sufficient to ice up and prevent him looking out (iceblock) through plane window dimmed with breath and, as a consequence of its deepfreeze  grip,  thwart the exploitation of rich deposits (the seep of adamantine tilth)

… and put a block on the speaker’s mental ability to compose and transmit his feelings: every warm, mouthwatering word of mouth.

 When  first and last lines are juxtaposed an ironic contrast is generated between Nature’s three-tongued glacier and the single-tongued human mouth – Man, acknowledged by most to be the major threat to the environment, is inhibited from reporting it.

• glacier: slowly moving ice mass;
• boulder: large, generally rounded rocks
• milt: elusive word – Irish does not seem to offer much; indo European suggests connotations of crushing and grinding; meanings to do with fish sperm seem out of context;
• wallow: flounder;
• delta: silted river mouth;
• shag-ice: ice that from a distance has a scarred pock-marked surface;
• ridged: with raised strips;
• rock-set: of solid, immoveable state
• grey-gristed: the colour and texture of ground corn;
• pelt: an animal’s outer skin;
• aeon: long, long time, since earth was formed;
• scruff: back of an animal’s neck
• dim: darken;
• seep: slow leakage;
• adamantine: unbreakable;
• tilth: tilled ground;
• mouthwatering: appetizing, tempting;

• 10 lines based on 10 syllables with 3 tercets and a final line; a loose, variable rhyme scheme;
• 6 lines contain 7 compound adjectives (Three-tongued) and nouns (boulder-milt)
• terms part geological/ part poetical: boulder-milt (related to melt?); shag-ice coarsely textured ice (see also scruff); vocabulary of cold: iceblock, deepfreeze; of melt: boulder-milt, wallowing, seep, mouthwatering;
• sound effects. In sentence (1) [i:] three/ we/ deep/ aeon; [əʊ] boulder/ wallowing; [ai] miles/ ice; alliterative effects of [w] aspirated what/ when; unaspirated we/ wallowing; [m] miles/ makes;
• compounds in line 6: alliterative grey-gristed  contains notions of colour, ground-up matter  (grist) and grinding materials (grit); earth-pelt ice stretched like a layer of skin; aeon-scruff roughness, the age of the universe;
• final lines contain assonances:[ɪə] undead/ breath; [i:] feared/ seemed/ Deepfreeze/ seep; [ɔː] warm mouthwatering  [ɪ] window dimmed/ tilth  [æ] adamantine and alliterative effect: [w]  warm mouthwatering word; 

• Heaney is a meticulous craftsman using combinations of vowel and consonant to form a poem that is something to be listened to.
• the music of the poem: thirteen assonant strands are woven into the text; Heaney places them grouped within specific areas to create internal rhymes , or reprises them at intervals or threads them through the text:

• alliterative effects allow pulses or beats, soothings or hissings or frictions of consonant sound to modify the assonant melodies; this is sonic engineering of the first order;
• for example, the final five lines are rich in alveolar plosives [t] [d]  nasals [m] [n], alongside sibilant variants [s] [z]  and front-of-mouth sounds: labio-dental fricatives [f] [v], bilabial [p] [b], continuant [w];
• a full breakdown of consonant sounds and where in the mouth they are formed is to be found in the Afterthoughts section;

• ‘Whch isn’t to say that Heaney has taken his eye off new and distinctly contemporary dangers. Whereas his earlier books gave a voice to the most violent phases of the ‘Troubles’, this casts wary glances at the peace and associates its fragility with other and even larger issues. His adoring of the natural world is intensified by worry about the planet – about ‘rising waters’ in Iowa and a melting glacier in Hofn.’ Andrew Motion in the Guardian of April 1st 2006
• The sonnet also teaches us something of Heaney’s personality: the man who on this occasion ‘came’ and ‘saw’, leaving us with an abiding feeling of his and by extension our vulnerability.