Cinder Cones and the Volcanic Complex of Santorini–Past, Present, and Future

Our class has been in awe of Santorini ever since the first time we laid eyes on this breathtaking Mediterranean getaway that is considered the most beautiful island in all of Europe. Most people that travel to Santorini also enjoy it’s beauty, but it was us ‘Pioneers of NAU In Greece’ (a title given to us by our volcanologist professor) that were fully able to appreciate it’s uniqueness through the study of it’s past, present and future Geologic timeline. Whether it’s viewing the powerful drop-off of the submerged caldera floor through a snorkeling mask or taking a guided boat tour to the tectonically heated hot springs; our magical experiences our always tied in with our studies. For me personally, one of the most jaw-dropping experiences was traveling to Red Beach on the southern peninsula of Thira and viewing a seemingly perfect eroded cross-section of a roughly 500,000 year old cinder cone volcano.

Red Beach Cinder Cone
Red Beach Cinder Cone

A cinder cone is defined as a steep, cone-shaped hill composed of fragmented volcanic material during a monogenetic, fire-fountaining eruption. As you can see from the above drawing, the cinder cone at Red beach is made up of multiple layers of cinders and volcanic flow from this monogenetic eruption. Each is slanted in the direction of the flow, which explains why they are dipping away from the vent. The composition of each bed is mafic to intermediate and represents a deposit from one of many reoccurring pulses that occurred during  the strombolian style of eruption. Red colored beds make up the majority of the cinder cone while darker colored black beds compose the outer 25% of the cone. The red color can be attributed to the oxidation of these layers by steam originated at the vent. Based on the amount of oxidation, we can imply that the steam that came out of the vent covered about 75% of the cone.

A red piece of scoria that was oxidized by steam from the vent. 1 Euro coin for scale.
A red piece of scoria that was oxidized by steam from the vent. 1 Euro coin for scale.
Small, eroded pieces of scoria that I collected in a Santorini-shaped bottle
Small, eroded pieces of scoria that I collected in a Santorini-shaped bottle

Throughout our three weeks here on Santorini, we’ve observed three cinder cones which are all a part of the unique volcanic complex that is present on this Mediterranean island. As the 6,000 degree Celsius (10,800 degrees Fahrenheit) core of the earth heats and melts the upper mantle and crust, the less dense magma makes its way to the surface of the earth. (1) In Santorini’s volcanic complex, the first lava to break through the crust had a low silica content, which means it was non-explosive and had a low viscosity (resistance to flow). This combination of elements is the recipe for the creation of a broad and flat shield volcano that is most commonly seen in Hawaii. As these eruption processes continue to occur, the magma becomes more gas-rich which causes an increase in explosivity and viscosity. A perfect example of this process is the Skaros volcano, which formed approximitely 67,000 years ago. It is characterized as a shield volcano but over time, more gas-rich magma rose through the vent which placed a cinder cone on top of the shield. Due to the outgoing nature of our class, I’m sure that we would make enormous sacrifices just to be able to catch a glimpsae of these volcanic wonders.

The cycle of magma evolution continues to repeat itself over time, creating a semi-predictable future.  It’s only been 3600 years since the last Caldera-forming eruption and another volcanic complex has already began to form starting with Palea Kameni, and now the most recent Nea Kameni shield volcano, an almost circular-shaped island just off the coast of the main island of Thira.  Thirty-six hundred years may seem like a long time but it is just a small fraction of the 50,000 year periodicity that characterizes the four caldera forming eruptions in this volcanic complex that occurred within the last 200,000 years.   We did not get to witness a small eruption on Nea Kameni (as we had hoped), yet our experience here on Santorini is still part of the never ending geologic timeline of the past, present and future.

One thought on “Cinder Cones and the Volcanic Complex of Santorini–Past, Present, and Future

  1. Joe – Thank you for a thorough summary of cinder cones. Those little red volcanoes are some of my favorite and most familiar (given we live amongst nearly 600 of them in Flagstaff).

    There are a few edits in here (from our review yesterday on the ferry) that didn’t get incorporated. Most importantly there is an image that you refer to missing between paragraphs 1 and 2. Check your notes in your field notebook and make those corrections.

    Additionally – the magma at Santorini is from melting at a subduction zone (much more shallow)….and not produced from heat released from the Earth’s core (that would be related to hot spots).

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