Table 1.

Weekly chronology of the main volcanological and terrestrial biodiversity events recorded during the eruption at Hoya de Tajogaite (La Palma, Canaries).

No. of week	Calendar dates	Volcanological event		Biodiversity event
		Main volcanic events	Impact of volcanic activity	Flora	Fauna
1	19–25 September	- 19 Sep.: Opening of a NW–SE eruptive fissure. Alternation of strombolian and vulcanian activity at several (> 4) vents. - Intense lava fountaining. - Very strong outburst of volcanic activity reaches the peak tremor and degassing values of whole eruption. - 24 Sep.: Effusive vent opens and builds an individualized structure on the NW flank; partial collapse of edifice.	- Gas and ash plumes occasionally reaching > 6000 m a.s.l. - 23 & 24 Sep. Rhythmic explosions with pressure waves. - Intense ash falls and rapid cm scale accumulations at ≈1 km from the volcano. - the first two lava flows reach a distance of 3.8 km and cover an area of 2.1 km2.	Rapid drying and wilting of fern fronds. Intense volcanic ash falls cause significant leaf perforation damage to understorey vegetation (in nearest 1 km). Canary pine trees severely affected in close vicinity of crater (≈300 m).	Many lizards die in their shelters in the face of advancing lava flows; Stunned birds; active bats recorded on S and N sides of lava flow (≈2.5 km from crater). Four dead mice found (Mus domesticus).
2	26 September–2 October	- Intermittent strombolian and vulcanian activity with strong explosive phases. - Lava fountains > 200 m high. - 27 Sep.: Short eruptive break (< 24 h); tremor intensity drops, weak passive degassing. - From the night of 27 Sep. eruptive activity returns. - 30 Sep.: a fumarole field emerges on the N flank. - 1 Oct.: opening of two new satellite vents to the NW of the eruptive fissure and intense effusive phases.	- 28 Sep.: Lava flows reach the sea (5500 m from the cone). - Massive ash emissions, especially on 30 Sep. - Volcanic bombs reach the base of the cone. Intense lapilli-falls in first 2 km from crater (~ 30 cm thick). - Vulcanian column > 6000 m a.s.l. - First important salts deposition on the pine forest soils (1200 m a.s.l.). - 1 Oct.: Poor air quality requires indoor confinement of the inhabitants of nearby towns of Los Llanos, El Paso, and Tazacorte (N of the Aridane Valley) (exacerbated by thermal inversion). - 2 Oct.: lava flows cover an area of 4 km2.	Pines in midst of lava flows apparently dead. Pine trees in vicinity of crater (nearest ≈500 m) clearly affected, mostly in S part of crater. Thermophilous woodland vegetation in front of lava flows still in good condition. Xerophytic scrub vegetation clearly affected. Laurel forest on SE face of island covered by abundant volcanic ash.	Many lizards die in their shelters under advancing lava flows. Other shelters collapse due to volcanic ash fall. Stunned birds, change in their predatory behaviour, e.g. kestrel (Falco tinnunculus) tries to catch small passerine birds and doves (Streptopelia decaocto). Six such attempts observed during these two weeks). No lizards seen. Small passerines tend to maintain their territories until arrival of lava flows.
3	3–9 October	High effusive activity with cyclic growth and partial collapse of the effusive vent draining the lava lake. Strong explosive activity (especially 5 Oct.) at more than 3 vents in the crater. - 5 Oct.: End of the activity at the two satellite vents - 9 Oct.: Edifice opens to the WNW	- 3–5 Oct.: Intense explosive activity showers the cone area with decimetric-scale bombs, up to 800 m from the crater. - Several confinements of people due to poor air quality in N zone of the Aridane Valley (3 Oct. and 7 Oct.). - Sustained ash and gas columns. - 8 Oct.: Lava flows cover an area of 5 km2. - Volume of emitted tephra: 8–9 Mm3.	First evidence of chlorosis in pine forest at more than 500 m N of crater (Llano de los Jables).	Sudden death of invertebrates. Birds become accustomed to new setting and display normal behavioral stereotypes. Long-eared owl (Asio otus) seen hunting 1 km from crater.
4	10–16 October	Very intense effusive activity from the NW effusive vent Lava lake overflows and partial obstruction of the channel, leading to overflows and diversion of the lava flows. - 11 Oct. onwards: Extension of the eruptive fracture and explosive vulcanian activity with phreato-magmatic component, to the SE of cone.	- 11&16 Oct.: Arrival of two new lava flows close to the sea (≈200–300 m). - Heavy persistent ashfall with very small grain size forms cohesive deposits in both the N and S sectors, severely affecting at least the nearest 3 km (previous 1949 lava flow). - High magmatic gas and aerosols content in atmosphere. - Air quality affected by burning greenhouses and biomass. - Oct.15: lava flows cover an area of 7.5 km2.	Pine forest chlorosis reaches 3 km S of crater (Los Romanciaderos) and undergrowth also severely affected after first ultrafine ash-fall on 12th Oct. Some branches of trees broken by weight of volcanic ash. Chlorosis of thermophilous woodland vegetation at least 3 km from crater. Xerophytic scrub reduced (> 60%). Lichens (Stereocaulon vesuvianum) on historical lavas of San Juan eruption (1949) covered by 5 cm-thick layer of ash.	First presence of grey colour in rabbit droppings (ingestion of vegetation with ash). Presence of clear vertebrate footprints in fine ash, at least 10 of 12 vertebrate species identified: 1 lizard, 6 birds and 5 mammals. Also, a minimum of two invertebrate species identified (millipedes and grasshoppers). At least 6 lizards seen adrift in midst of an extensive ash surface with no food and its very few remaining shelters obliterated by volcanic ash.
5	17–23 October	Highly effusive activity with lava fountains and channel overflows covers new areas with lava. - Vulcanian-type activity remains important at several vents. - Structural reconfiguration of the effusive vent with instability, collapse and draining of the lava lake. - Oct. 23: Opening of new vent on the SE flank.	- Progression and lateral extension of the northern lava flow. - High magmatic gas and aerosol content in the atmosphere. - Air quality affected by greenhouse and biomass burning. - Oct. 23: lava flows cover an area of 8.9 km2.	Substantial layer of ash (≈40 cm) deposited on vegetation nearest crater (first km). Pine forest understorey vegetation severely affected. Heavy fall of pine needles on the ground, outside their natural phenology.	Rabbits eating resprouting introduced Cenchrus orientalis, a rare case in the Canaries. Continued presence of volcanic ash in rabbit droppings, also in lizard droppings for the first time. Insects scarce, but grasshoppers frequently seen, apparently the arthropods that best withstand the eruption.
6	24–30 October	- Strong effusive and explosive activity. - Instability of the effusive vent causing overflows. - Oct. 26: Partial collapse of the summit of the main cone, followed by heavy pyroclasts showers. - Fumarole activity on the E flank of the main edifice. - Oct. 29: Strong vulcanian activity (shockwaves and lightning).	- Profuse ash falls in the W and NW areas (humid on Oct. 29). - Oct. 24: New lava flows from (1) the Oct. 23 SE vent and (2) a new vent on W flank reaching the coast at end of week. - Oct. 27–28: Poor air quality (SO2 content). - Oct. 30: Lava bombs reaching base of the eruptive cone; lava flows cover an area of 9.7 km2.	First episode of acid rain recorded on arrival of humid rainy trade winds. First resprouting in pine-forest understorey (e.g. Chamaecytisus prolifer). Second great crash of xerophytic scrub, e.g. reducing Euphorbia canariensis to ≈10%. Surprisingly, lichens in pine forest do not yet seem affected.	The endemic ubiquist Pipistrellus maderensis is the most abundant bat, but mainly detected at lower elevations, linked to banana plantations. They are almost absent in pine forest and thermophilous habitat A difficult period for Sauria in general. At least 3 geckos are seen at night in a delicate physical condition, adrift in an extensive ash surface.
7	31 October–6 November	- Strong effusive episodes on 1, 2 & 6 Nov. - Intense vulcanian episodes on 3 and 6 Nov. - 1 Nov.: Strong fumarole activity on the S flank. - 3–5 Nov.: Drop in seismic activity. - 5 Nov.: First yellow sulphur deposits on the main cone. - 6 Nov.: New lava flow from the effusive vent.	- Lava channels overflow on the southern side of lava field. - Heavy ashfalls to the S of crater cone. - Substantial degassing, particularly from effusive vent, leading to dense atmosphere and poor air quality. - 3 Nov.: Second ultrafine ash-fall. - 6 Nov.: lava flows cover an area of 9.9 km2.	Thermophilous woodland and xerophytic habitats seriously affected by lava flows. Damage caused to trunks of endemic succulent plant Euphorbia lamarckii is clear evidence of direct physical damage by intense ash-fall.	Herbivory of threatened endemic plant Cicer canariensis by introduced rabbits. The vertebrate community is at an extreme point in terms of feeding. Clear proof is rabbit herbivory of plants they rarely consume, such as Aeonium davidbramwellii.
8	7–13 November	- Continuation of intense effusive activity with progression of the lava flows. Some reach the sea and rapidly build a large new platform. - Alternation of vulcanian and strombolian activity inside the central crater. - 9 Nov.: Notable fumarole activity. - 12 Nov.: Lava lake overflows at the effusive vent. - 13 Nov.: Yellow sulphur deposits on the S flank.	- Second arrival of the lava flows in the sea (S side). - Mixing of various effusive and vulcanian plumes: hydrothermal component, plumes from the lava flows and from the coastal lava delta. - Strong winds (1) blow the plume down to the ground, causing very high gas concentrations at ground level and (2) remobilize previous ashfalls. - Episodes of high gas emission (SO2 and HCl) towards the pine forest and near the crater. - 13 Nov.: lava flows cover an area of 10.2 km2.	Damage by acid aerosols is clear in pine forest located to S of volcano. It reaches ≈7 km from crater, impact extends in a mosaic pattern, causing a 2nd great fall of pine needles. Chlorosis of pines reaches 1 km from N side of crater.	Feral cat scats contain remains of the scarce endemic lizards (Gallotia galloti) A 2nd ultrafine ash-fall reveals tracks that confirm feral cats are abundant and widely distributed. At the coast, first observations of seagulls Larus michahellis taking advantage of dead benthonic marine animals. The heavy lava flow over and down the sea cliff may destroy nests of the petrel Cory’s Shearwater, Calonectris diomedea.
9	14–20 November	- Continued high effusive activity with progression and spreading of the lava flows. - Alternating strombolian and vulcanian activity at the central cone with intense vulcanian phases every day except 20 Nov.	- 15 Nov.: A third lava flow reaches the sea 150 m S of the 2nd lava platform. - 15–17 Nov.: Large ash emission in both the N-NW and S-SW areas, due to climatic conditions. - First major windstorms drag the plume on the ground, causing very high gas concentrations (especially on 17 Nov.). - Large gas emissions. - 20 Nov.: lava flows cover an area of 10.7 km2.	Xerophytic scrub highly reduced (≈10%). One of the most common shrubs in thermophilous habitat (Rumex lunaria) begins to resprout after second rainfall in previous days. Vegetation in same elevation belt is highly deteriorated < 2 km from crater.	Some saurians (lizards and geckos) found dead, apparently from starvation. A large number of benthonic animals appear on the rocky beach and this resource is exploited by gulls and waders.
10	21–27 November	- High effusive activity: (1) causing overflows of lava channels and (2) at new vents, both extending the area covered. - Alternation between strombolian (200 m high lava fountains) and vulcanian activity. Strong episode on 23 Nov. accompanied by substantial ashfalls. - High fumarole activity. - 25 Nov.: Opening of multiple effusive vents along a W-E fissure to the S of the main edifice.	- High concentration of gases reaching the pine forest. - Large salt precipitation spots appear W of the cone. - 22 Nov.: A new lava flow reaches the sea N of the lava field (close to Tazacorte harbor). - 24 Nov.: lava flows cover an area of 10.9 km2. - 25 Nov.: New lava flows in the S (destruction of Las Manchas graveyard).	Upper belt of pine forest (900–1300 m a.s.l.) clearly affected after 2nd rainfall in previous week A large gas emission causes severe chlorosis of pine forest S of cone. Its encrusting lichens are cleaner (less ash) due to recent rainfall.	Dead saurians (lizards and geckos) continue to appear, apparently from starvation New feeding behaviour in raven Corvus corax, eating invertebrates (millipedes, beetles and silverfish) under bark of rotten branches.
11	28 November–3 December	- 28 Nov.: Formation of a new eruptive vent NE of the crater, with intense strombolian activity rapidly building a spatter cone, accompanied by voluminous highly fluid lava flows. - Decrease in intermittent activity at the other vents. - 1–2 Dec.: intense explosive activity at this new vent with powerful shockwaves. - 3 Dec.: Focused on the spatter cone, a set of fractures dissect the edifice down to its S-facing base. Decrease in volcanic activity at the spatter cone.	- Extension of the area covered by the lava flows. - Poor air quality in nearby towns, El Paso and Aridane Valley. - 3 Dec.: lava flows cover an area of 11.8 km2.	Plants in thermophilous woodland (especially Sonchus hierrensis and Euphorbia lamarckii) start to resprout notably, after 2nd heavy rainfall. Pines in lower S area of volcano (Las Manchas) are clearly affected by acid aerosols from volcano.	The limiting situation of some birds of prey: kestrel Falco tinnunculus with unusual prey, a rat. The vegetation refuge of many passerine birds in the gardens of Las Manchas cemetery is seriously affected.
12	4–10 December	- 4 Dec.: New extension of the Nov. 25 eruptive fissures towards the W, opening several effusive vents SW of the edifice. - New lava flows reaching the S of Todoque (S zone of the Aridane Valley). - Relatively weak activity. - Significant degassing (1) from the effusive vent, (2) from ground fractures in the SW sector.	Poor weather with rainfall (9 Dec.) and strong winds remobilize ash and draw the gas plume down, causing air quality alerts. - Extension of area covered by the lava flows: 12.2 km2 on 9 Dec.	Abundant lichens (fruticose thallus: Usnea articulata) fallen from trees in pine forest (1200 m a.s.l.). Decline in physical condition of pine trees in same zone, while highly affected at lower elevations towards S (Las Manchas). Although pines appear to be in a poor vegetative state, the needle bases are still green, indicating they are still alive.	Appearance of many dead marine species (mainly crustacea, starfish and moray eels) at the volcanic proto-beaches. Intense feeding activity of seagulls.
13	11–14 December	- Mild effusive activity. - 12–13 Dec.: Strong vulcanian episodes (column > 6000 m) with bombs ejected rolling down to the base of the cone, preceding the end of the eruption.	- A new lava lobe reaches the base of the cliff at La Bombilla (S end of the Aridane Valley). - Third episode of ultrafine volcanic ash. - Significant degassing from the central edifice and from the lava flows and punctually along fractures from the cone to the coast near Puerto Naos and La Bombilla. - Dec.14: lava flows cover an area of 12.4 km2.	Pine forest S of volcano clearly deteriorated, with visible chlorosis, mainly caused by episodes of acid rain and gas. The last lava flows reduce xerophytic scrub < 5% of the original surface area. All endemic Euphorbia canariensis have disappeared.	Pipistrellus maderensis is confirmed as the only bat species recorded during this eruption. Five dead birds and two rats found at the coast, probably caused by local gas pockets. First flocks of Serinus canarius present at 300 m from crater.

Areas covered by lava flows were determined by Copernicus.