Good morning! It’s 6:22am! I’ll get through questions quickly and before I start sharing my research, I need to highlight the official volcanic hazard map of La Soufrière on the main island of St. Vincent. The following information has been featured on @uwiseismic and NEMO (1/?) https://twitter.com/scarlett_jazmin/status/1344033589969747974

The red zone is Hazard Zone 1 which means “Very High Hazard”. This means areas from Fancy to Georgetown could experience maximum damage from 2 deadly hazards Soufrière can produce: volcanic mudflows called ‘lahars’ and ‘pyroclastic density currents’ (PDCs). I will define the 2.

Lahars or volcanic mudflows are a mixture of water, volcanic material and debris and are channelled down the river valleys directly connected to Soufrière, the most prone is Rabacca Dry River east of the volcano. What is dangerous about them is that they can happen before...

...during and sometimes long after an EXPLOSIVE eruption occurs. This happened in the previous explosive eruptions of 1812, 1902 and 1979 (research about these events coming after this thread). However, lahars DID NOT happen for the effusive event of 1971-1972.

The other hazard is pyroclastic density currents (PDCs) or the ‘old’ volcanology term you might be familiar with is “pyroclastic flows”. These are super hot, super fast (generally) gravity-driven volcanic ash, gases and debris flows. They are dangerous due to being...

...not only channelled down most river valleys on the western, northern and eastern sides of Soufrière, but also because they can blanket entire sides of the volcano, travel ‘uphill’ and surmount barriers and flow over water. For Soufrière, this occur when there is ash column...

collapse brought on by gravity occurs during EXPLOSIVE activity. This occurred in 1812, 1902 and 1979. BUT NOT during the effusive episode of 1971-1972, similar to what is happening now. PDCs are faster than you think. They can go up to 300 miles per hour.

Additional hazards in the red zone to be concerned about are volcanic ballistics and bombs that are bits of old and new volcanic material thrown out by the volcano and also volcanic ash up to 30cm deep. However, these occur from EXPLOSIVE activity at Soufrière, please remember.

The next hazard zone is Hazard Zone 2 (orange). This area that would affect Chateaubelair on the Leeward side, and about up to Byera, could experience smaller pyroclastic flows (PDCs), within 5 km be impacted by volcanic ballistics and bombs and between 10-30 cm of ash...

...however, in large EXPLOSIVE eruptions similar to 1902 or even bigger (I will share mine and others research on this eruption after this thread), the orange zone is treated as the red zone. But please remember, this is in explosive eruptions NOT what is happening right now.

Next is Hazard Zone 3 (yellow) this also known as the “moderate” zone. This includes on the Leedward side between about Westwood to Barrouallie, and Windward side about Chester Cottage to Union. In this zone, only ash up to 5-10cm, minor volcanic earthquakes and (potential)...

...lightning strikes from the volcanic ash cloud would happen (lightning will also occur in the red and orange zones BUT depends on the direction of the wind). This was not a feature in my research, but this is official information associated with the SRC and the hazard map.

Lastly, Hazard Zone 4 (green), is “Low Hazard”. These are all areas south of Barrouallie on the Leeward side and about Union on the Windward side, and also include the Grenadines. This area would receive up to 5cm of ash but if not managed, can impact crops and water supply.

Impacts on crops was a focus of my research, so will talk about that later! However just to highlight, if ash is not removed effectively and promptly from roofs, it can cause collapse and can damage crops and fruit. Banana and plantain can be especially impacted, so take care!