The transformation of St. Vincent commenced with a cracklike thunder followed by a storm of ash late last week. Within the passage of a day, the once vibrant city of Richmond Vale on the island of St. Vincent was coated in a thick, monotonous layer of ash and soot. As the eruption of La Soufrière continued early this week, the accumulating ash dulled not only the lush green around the city, but also made a dramatic spectacle of the area in infrared satellite images. New satellite images showed the extent of the ash's reach as of April 13, the day after Monday's "huge explosion," which created an ash cloud that turned day to night as far away as Barbados. This third explosion since Friday also marked 42 years since the volcano had last erupted back in 1979. An estimated 16,000 to 20,000 residents -- up to 20% of the island's population -- have been displaced by the eruptions, according to the World Food Programme, the United Nations said in a press briefing this week. Initial estimates indicated around 3,500 people were in shelters as of April 12 with other evacuees housed in private homes. Even after the government of St. Vincent declared a red alert and issued an evacuation order for the northern areas of the island on April 8, Coast Guard crews rescued evacuees near the volcano by boat. On Wednesday, the St. Vincent and the Grenadines National Emergency Management Organization (NEMO) announced the volcano's explosive eruptions continued, and La Soufrière had once again begun to generate pyroclastic density currents. These currents, also known as pyroclastic flows, are made up of a mixture of ash, rock fragments and gas, and can travel down volcanoes at speeds of up to 120 mph. Richard Robertson, a geologist with the University of the West Indies Seismic Research Centre, warned on an update over NBC Radio on Wednesday that these flows cannot only effortlessly reach farther distances after previous flows have cleared the way, but can even pose a hazard when reaching the ocean. When the pyroclastic flows hit the sea, Robertson explained, they tend to accelerate, moving forward not just in a line, but spreading out as they boil the water. "Therefore it moves faster in all directions, and it moves very quickly towards anything that is in its way, really," Robertson said. "So that's why when we think of the hazards from pyroclastic flows, particularly on islands like ours -- we can't think of it as just being on land. We have to think of it as also being extended outside, beyond the land." Cars drive under the ashes raining from the sky over Black Rock, the main road on the outskirts of the capital city Bridgetown, Barbados, Sunday, April 11, 2021, due to the eruption of La Soufriere volcano arrived from the neighboring island of St Vincent, which is about 100 miles to the west. (AP Photo / Chris Brandis) He added that people working around the areas where pyroclastic is occurring, such as those in the fishing industry, need to consider a buffer of a mile or two out to sea where the red zone extends. The ongoing explosions and accompanying ashfall are likely to continue to occur over the next few days, according to NEMO. In addition to the dangers of pyroclastic flows, NEMO officials are also asking people to refrain from playing in the ash after receiving a few reports. "Though ash may fall like snow, it is deadly," the organization said. Volcanic ash is comprised of jagged, sand-sized pieces of rock, minerals and glass, and can taint water supply, damage crops, and even cause health concerns for humans. These can range from respiratory issues, such as a runny nose or a sore throat, itchy or bloodshot eyes, or even scratched eyes.