Lava Flows: More good than harm?

Upon arriving at the port of Santorini on the ferry, I look up noticing ridged layers of tan, brown, and beige blanketing each other into mountainous volcanoes. Each hue and layer tells a different story of formation, magnitude, and volcanic material present during the eruption. Every layer is unique in that no layer is like any other. Some are supported by ash and pumice, while others are completely supported by lava flows. I was thrilled to undertake this new adventure at such a young age, but there is a daunting feeling in the back of my mind to know that when this caldera erupts once again, nothing that we know of it will remain.

As someone who has never traveled outside of the United States my entire life, Santorini is quite different from what I have ever known. A great majority of my life I have only lived in Phoenix, Arizona, an immensely dry desert that is flat. Phoenix is trapped in a large valley that is very easy to build upon. Houses and structures may be organized into a neat perfect rows and columns, similarly to grid, unlike the houses and villages of Santorini. To say that the landscape of Santorini is unique would be an understatement, it is a very hilly steep island that is suspended above water. The houses are suspended thanks to highly resistant lava flows!

(Figure 1) Picture of an oxidized, or stained with iron, lava flow on the way down to Old Port in Thera

Lava flows are streams of non-explosive magma that ooze out of volcanoes in the event of an eruption (Figure 1). Basaltic flows race down the sides of a volcano and solidify where areas are less steep. In contrast to basaltic flows, rhyolitic flows bubble out of vents such as toothpaste would out of a bottle. Rhyolitic flows harden closer to the vent as opposed to basaltic flows. Eventually many layers of solidified lava blanket one another, creating massive mountains and volcanoes that are as tall as 400 meters high, such as Mt. Profitis Elias, and short as 198 meters, such as Cape Plaka (Figure 2) [1].

(Figure 2) Cape Plaka contains some lava flows but it is mostly composed with stacked layers of pumice and ash; 198 meters high

Lava flows are not just ‘pretty’ striped features on a volcano, rather, they contribute to where and how structures are built. I bet you never thought geology controls this, but it actually does! Because Santorini is suspended above water, homes must be built ‘into the walls’ rather than merely on top of hills (Figure 3). This is because lava flows are resistant to build on.

The bottom layers are composed of alternating weaker rock of pumice and ash. The surfacing layers are capped by lava flows. Without lava flows, building houses or villages would not have been attainable. If someone tried to build a house solely on top of ash and pumice, the house would slide right of the cliff. Lava flows act as a sturdy foundation that holds weaker pumice and ash in place. On the drive to Oia, there are no houses because there are no lava flows present. Again, if houses were built there, they would slide off the cliff because there is no solid foundation to hold it in place. Building on top of lava flows is also convenient because they are resistant to weathering. After many storms and rain, lava flows are still very stable.

(Figure 3) Oia, Santorini; notice how buildings and shops are stacked and deposited into the walls. Buildings are not constructed into rows and columns

It is incomprehensible to think that Santorini was once an uninhabitable island of pumice and ash beds. 200-180 thousand years ago the first caldera collapse occurred, creating just the beginning of an island filled steep slopes topped with glistening white and beige structures. Before my first week in the field, I never gave much thought about much geology impacts how and where houses or buildings are constructed. Upon arriving in the port of Santorini, I was completely wonder struck about the organization of homes on Santorini! Shops and structures are scattered around the island in an unusual precise way all because of lava flows. Next time you make a trip to an island, stop and think to yourself about the layout of the island and what might have contributed to that.


[1] Friedrich, Walter, L, 2009, Santorini: Denmark, Aarthus University Press, 312.

5 thoughts on “Lava Flows: More good than harm?

  1. Sadie – You improved the explanation of the lava flows capping the weaker pumice and ash layers. One critical error is that Figure 1 is a welded tuff (see Jenna’s blog) not a lava flow. Additionally, the rock layers beneath Cape Plaka are mostly pumice and ash beds. I’m glad you are giving more thought as to how geology controls slope stability and where structures are built. Hopefully over the next two weeks it will be very clear as we learn more about all the volcanic deposits around the island.

  2. Hello Saide,

    I enjoyed your post this week as it seeks to explore natural processes and how they impact civil logistics; that many tend to take for granted. Your post demonstrates a clear voice in a discussion centered around lava flows and how they shape life for the island of Santorini. While the post is well written, informative, and provides an intriguing narrative; there are some areas that I had to read through a few times in order to get the gist of your post.

    The opening is written in a way that provides what the post will be about and introduces your narrative. However, I don’t believe your post mirrors the discussion presented in your title. While the post discusses lava flows and how they allow for residents to build or not to build, your discussion is more expository than argumentative; as your title suggests. Having read your post, a more appropriate title might focus on how lava flows significantly impact the layout of the city and the daily life of the people. As for the personal narrative, this is established in a subtle manner that makes your reader want to continue learning about your travels, nice job.
    My only suggestion would be to clearly incorporate your topic into the introduction of a post. You begin to do this in paragraphs 1 and 2 but, as an outside reader, I cannot clearly identify your topic until the third paragraph. In presenting yourself and your impression of the island, include the topic that you will be discussing. This way your reader understands what the post will be about, why you’ve written it, and hopefully they learn something from it. Similarly, paragraphs 4 and 5 would benefit from language clearly stating the main ideas of those paragraphs and connecting them to the topic of the post. Think of this as relating main ideas in a paper to your thesis.

    Another area to clearly state your ideas would be the end of the first paragraph. The last sentence is related to your topic but its place at the end of the paragraph neither states your purpose for writing or transitions to the next paragraph. In future posts, use the last sentence in paragraphs to reiterate main ideas of your post or to transition to another point of discussion. Another area to improve clarity is paragraph 3. In this partition, you discuss two types of lava flow, however the post jumps into defining these types of flow before making them directly known to the reader. To assist your reader, use a sentence like: “There are two types of lava flow,” then proceed to define the two. A sentence like this would make the paragraph’s purpose known while also allowing the reader to understand they’ll be reading about two different types of flow.

    For your next post try to communicate your ideas in language that is succinct and says only what needs to be said. Another area to cut down on language would be your description of Phoenix. Rather than provide your reader with thorough description of a desert, I believe that you are safe in simply stating that Phoenix is a vast, Arizona desert.
    Generally, your post exudes style but could benefit from clarity and reiterating main ideas. For instance, your conclusion clearly states what your post was about and how the island has impacted you. These ideas need to be in your opening paragraphs as well.

    Overall, solid and informative post. Your narrative and supplement of visuals intrigued me as a reader. Your post allowed me to learn of geographical structures and their impact on civilizations from a point of logistics, architecture, and general safety.

    Happy Writing,

    Jose Martinez

    1. Jose,

      Thank you so much for taking the time to read my blog! I greatly appreciate your feedback and suggestions. I’ll be sure to incorporate more of your ideas in my next blog post.

      Thanks again,
      Sadie Segovia

  3. Hey Sadie,

    Your topic is a great start for a class that is supposed to be an extension of Geologic Disasters. Your post does a good job at enticing your readers to think about how human construction is impacted by how geology varies location by location.
    You provide relevant examples to the science you’re explaining to your readers which is good. When you are discussing topography of the island and where villages are located, a figure showing a topographic map of the island with the sites your referenced labeled would be beneficial to your readers.
    Geology may impact where people build structures, but we don’t always stay away from geologically risky areas. Humans sometimes do what they want for immediate gratification. Do you know of any villages where the buildings are in geologic hazard zones? And what possible events could cause the buildings to ‘slide off the cliff? These are topics that could be further developed to educate your readers on hazards to consider when traveling to volcanic islands.


    1. Alex,

      Thank you for your feedback! Thank you for bringing the last two questions to my attention. I hope to address these questions in a future blog post.

      Thank you,
      Sadie Segovia

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