Volcanic Weather: A Storm of its Own

When I think about volcanic eruptions, I picture overbearing darkness, flowing lava, falling ash and shaking ground. What I don’t picture is a volcano creating its own weather. However unlikely it may seem, this phenomena holds true for the Minoan eruption here on Santorini. During the Minoan eruption, volcanic weather may have helped shape deposits as well as creating other hazards associated with volcanic eruptions.


Volcanic weather is produced when the hot eruption column rises buoyantly into the atmosphere. When it is released, it incorporates the ambient air, making the column expand into a massive cloud. In synchrony with the eruption, the cloud then rises and cools producing rain fall and volcanic lighting.

Natural phenomenon of volcanic lightning at the eruption of Chilean volcano Chaitin May 6, 2008. Photo: Gutterriez C.
Natural phenomenon of volcanic lightning at the eruption of Chilean volcano Chaitin May 6, 2008. Photo: Gutterriez C.

It is thought that scour channels may be produced by volcanic weather. A scour channel is an erosional feature of volcanic rocks that is deposited by flowing water. When analyzing scour channels in the Minoan eruption deposits here on the island, my classmates and I observed a sloping feature with larger lithic fragments at the bottom and smaller fragments at the top, similar to a riverbed. We posited that the rain produced by volcanic weather created the scour channels, which would explain the similarity to a riverbed.

Here is Carly standing in front of the scour channel we saw. You can look closely to see how the larger rocks form the slumping bed, similar to a riverbed which caused it.
Here is Carly standing in front of the scour channel we saw. You can look closely to see how the larger rocks form the slumping bed, similar to a riverbed which caused it.

Scour channels are visible at Cape Mavropetras (northern Thera) and near Ancient Akroteri (southern Thera) . I observed and described the scour channels of phase 4 of the Minoan eruption on Northern Thera when we composed outcrop sketches there. Carly Stefano’s latest blog “A Geological lesson for the Little Ones” describes in detail the phases of the Minoan eruption. Our sketches were particularly helpful at this location because we were able to show details of the physical view of the landscape. The sketches help paint a picture of how the land looks, but also help connect the science of the volcanic weather.

This is a scaled sketch of the scour channels we saw in the field. Thankfully you don't need to be an artist to accurately draw these outcrops.
This is a scaled sketch of the scour channels we saw in the field. Thankfully you don’t need to be an artist to accurately draw these outcrops.

Now that I am able to interpret the land better with more knowledge, I am able to form a picture in my head of what the actual events could of looked like. We know that there were huge amounts of ash and pumice falling from the sky, as well as lithic fragments varying in sized being projected as well. Amongst this terrifying image of falling sediment, there is also rain pouring down. I would assume that it was a vast amount of rain because of the size of the sediment deposited in the scour channel. From our geological disaster class, we know that flash floods move at rapid speeds, taking anything in their path. This is what I imagine when I think of how the scour channels were formed in the deposits (1).
The Minoan eruption affected history in many ways and understanding the hazards created by volcanic eruptions is important for our future understanding. Throughout our classes here on Santorini, we have learned various ways of how to accurately describe the rocks and land before us. Our sketches and descriptions help those who read our field notebooks make their own interpretations. Being able to describe the phases and explain how scour channels are created will aid in the preparation for a similar eruption. Since it is impossible to predict an eruption, learning about these naturally occurring hazards is the best preparation we have against volcanic disasters.

Friedrich W.L., 2009, Santorini: Volcano, Natural History, & Mythology, Denmark: Aarhus University Press, P 231.

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One thought on “Volcanic Weather: A Storm of its Own”

  1. This is your most well-formulated and thought out post yet! Good summary and visualization of what volcanic weather may look like. The scour channels tell an important part of the story in that the rain (regardless of how it was produced) was occurring at the same time the volcanic material was deposited. Since there are no soils or unconformities above the channels and the channels exist at many different stratigraphic levels, we can assume that water was shaping the surface during and just after the 4th phase of the eruption.

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