A super eruption on the Toba volcano produced a bottleneck in the human and in many animal species. How could it be that the eruption of a volcano almost wiped out many animal species?
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https://en.wikipedia.org/wiki/Toba_catastrophe_theory
> The Toba catastrophe theory holds that this event caused a severe global volcanic winter of six to ten years and contributed to a 1,000-year-long cooling episode, leading to a genetic bottleneck in humans.
Particles from the volcanic eruption spread through the atmosphere, obscuring the Sun. This results in a climate change which severely hurts animals and plants.
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If ashes block the sun, the planet cools down, and the average global temperature decreases. The difference between today and the ice age average temperature is less than 10 degrees. That’s why scientists are freaking out that the planet might warm up faster than one degree per century. One degree increase on average means at least 10 degrees increase in certain areas. We cannot withstand such huge changes in temperatures. In 300 years, it might not be possible to live comfortably anymore. Even today, during the summer, on more than half of the planet, you need to protect yourself from prolonged direct sunlight in order to not risk your health.
In fishponds today, many of the breeds of fish that are grown are different than 50 years ago because, during the summer, fish die because of high temperatures. Water at high temperatures holds a lot less oxygen, fish sufocate, and they can no longer regulate their temperature and die from heat stroke. Many ponds, besides filtration systems, have cooling systems too, in order to keep nature from killing them.
Volcano produces smoke. Smoke blocks out the sun. No sun means plants start to die. No plants to eat means that herbivores start starving and dying. Less herbivores mean that carnivores start starving and dying.
[No such population bottleneck happened](https://www.sciencedirect.com/science/article/pii/S1040618220303335), and the climate impact of the volcano [was “negligible”](https://www.sciencedirect.com/science/article/pii/S2590056022000044).
The Toba population bottleneck is a 30 year old theory based off the very earliest days of ancient DNA research, and is now known to be false. We’re about ten years behind the science when we talk about this theory.
I’ll do my best Eli5 by comparing to a sneeze.
when the Toba erupted, it was like a GIANT HOT sneeze.
When we sneeze, we send out lots of snot particles big and microscopic, in every which way with a human amount of force.
Now, imagine something the size of the earth sneezing. The force or power of the sneeze is greater, so all those big and small particles go flying further. It is important to mention the heat because the heat allows the rocks to become liquid. When Toba sneezes, instead of snot coming out, it is fast, hot, liquid rock that comes in all kinds of sizes, but a shocking amount is super tiny microscopic.
Just like a sneeze can be affected by a fan, this microscopic rock dust is affected by the wind and can spread a huge distance. Much of that dust was forced above the clouds. That microscopic dust can also stay aloft in the air for years because the wind will continue to carry it.
With all that dust in the sky, it blocks out a lot of sunlight. Plants require sunlight to grow. Some plants will die, and others will grow at a very, very slow pace.
Plants are also the foundation of the food chain. When you remove the foundation, everything becomes unstable. Unfortunately, just as the plants starved, as did most living creatures.
Living things like sunlight. Volcanic eruptions produce smoke that blocks sunlight. Super eruptions produce lots and lots of smoke. Life no like.
Volcanoes throw a lot of rock, dust, ash and other crap into the atmosphere. These block sunlight from getting to earth’s surface, which reduces global temperatures. The loss of sunlight also adversely affects plant growth (see 1816: the year without a summer)
It’s suspected that if the Yellowstone supervolcano were to erupt then it would make the northern hemisphere almost completely uninhabitable and cut global temperatures by 20°C, triggering a short ice age.
People have already disproven the Toba bottleneck. In general, however, the idea is that:
* a lot of dust in the air lowers the amount of sunlight coming through
* plants get less sunlight, so they don’t grow as well
* less food for herbivores means that there’ll be less herbivores over time.
* Less herbivores means less food for carnivores. There’s a double whammy here because underfed herbivores will be easier to catch and won’t reproduce as much, causing them to be overhunted very easily
* And now there’s less of everything.
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