Tickets! Tickets please!
Oh, hello there! Are you here for the geology tour of Santorini? I’ll be taking a group on a tour around the island to the see the active volcanic dome, the Akrotiri Archaeological site, different beaches created by volcanic events, and much more! It all starts here at Fira port and all you need is a tick-Ah! I see you’ve already got one. Perfect! Climb aboard my boat, the Gem of the Sea, and let the adventure begin!
As we’re sailing to our first stop, I’d like to explain a bit about the Minoan eruption to you. The Minoan eruption was the last caldera forming eruption, which occurred in 1613 BC +/- 13 BC, and it consists of five phases, from phase 0 to phase 4. We will only be seeing phases 1, 2, and the upper part of phase four on our journey, which I will explain later. If you’d like to learn more about the other phases, check out Pocket Full of Rocks by Leah Brennan or Beautiful Place with a Frightening Reality by Sarah Nolt-Caraway on nauingreece/wordpress.com .
Alright folks, here we are at our first stop: Nea Kameni! Since it is an island in the middle of the caldera complex of Santorini, it is only accessible by boat. This 3.4 km^2 island is an active dome, which is a non-explosive type of volcano high in silica that builds itself upwards. These can become quite steep, as shown in the image of the 1950 dome above. The darker lava flows are newer and the grey rocks are older lava flows. These older flows have been weathered enough over time that vegetation has started to take root in its soils. The last eruption in 1950 created a small, volcanic dome that pushed up near the center of the Nea Kameni. This produced small earthquakes, some minor explosions, and ash and steam plumes that originated from the vent, which is where the magma is exposed to the atmosphere. The eruption also caused an increase in fumarole activity, which are volcanic gases that seep out of the ground. (1)
Not to worry folks, we have several systems put into place to warn us of any new volcanic activity, including seismometers and gas flux monitors. What are those you say? Well, when magma moves underground, whether its to a new location or closer to the surface when it is about to erupt, it creates tremors in the rocks. These tremors are picked up as earthquakes by the seismometers on Nea Kameni. Numerous earthquakes can be caused before a volcano erupts, so geologists use this data to predict when the next eruption may be. Gas flex monitors are also put into place to measure any increase in magmatic gases, such as sulfur dioxide or helium, in fumaroles and hot springs, which are created by magma heated water seeping out of the ground. An increase in magmatic gases means the magma is close enough to the surface to release gases and could indicate that the volcano is about to erupt.
From January 2011 to May 2012, a Crisis Period occurred in which new volcanic activity started. The seismometers picked up as many as 50 earthquakes under magnitude 3.5 per day and fumaroles and hot springs transitioned from releasing 15 tons of magmatic gases per day to 35 tons of magmatic gases per day. Thankfully, there hasn’t been a significant increase in new volcanic activity since then. While we have a 1 in 20,000 chance of a Minoan style eruption occurring in the future, it is most likely that a hydrothermal explosion, which is induced by water, will occur in the near future. If you’d like to learn more about he crisis period, take a look at Sarah Nolt-Caraway’s blog as mentioned above.
Oh my what was that! Oops, sorry! That was just my stomach; all this talk about volcanoes is making me hungry! We should get a head start to our next location now folks; its all the way on the southern Akrotiri Peninsula!
Here we are: the Akrotiri archaeological dig site! For those of you who have seen Indiana Jones, don’t worry. There aren’t any large rolling boulders or booby traps here, but I’d advise you not to touch anything!
These ancient structures were built by the Minoan people who first settled here from Crete in the 5th millennium BC. The excavated area is a mostly residential urban center with one major street and several connecting alley ways. No agricultural lands have been discovered here, but there is an ancient storage area and market in the northern section. Many of the buildings were 2 to 3 stories high and some had frescoes painted on the inside, which have been removed and preserved in the Archaeological Museseum in Athens, Greece. The houses even had drainage systems, which are evident by the terra-cotta pipes in the walls, including the world’s first siphoning toilet! Only an estimated 1/10 of the entire settlement has been excavated.
What caused these buildings to become preserved so well? Geology of course! Pumice fall from phase one of the Minoan eruption caved in the wooden roofs of the houses, but surrounded the walls and objects in the structures like snow. This 400 degree Celsius pumice “fired” the pottery, frescoes, and houses as if they were in a kiln and preserved their colors. Casts of olive wood trees made from the pumice can also be seen at the archaeological site since the pumice surrounded the trees and preserved their features. After the trees were surrounded by the pumice, they decayed and left behind a cast. The wooden material used for the houses also decayed in the same manner, which is why there are no remaining roof materials found here.
The second phase of the Minoan eruption, however, did not have a snow-like pumice fall, Instead, its pumice and lithic materials bulldozed the land in a turbulent flow known as a pyroclastic surge! This destroyed anything that was not protected and surrounded by phase one of the eruption. If you’d like to know some more about the Minoans and whether or not they made it out in time before the Minoan eruption, talk to my friend Rachael and read her blog: Ignorance is Not Bliss: What Doomed Pompeii and Saved Akrotiri.
Our next stop is Red Beach, which is the inside of a cinder cone! Those of you who have read about some of my travels here in Volcanoes: A Piping Hot Mess, know a little bit about when and how this volcano formed.
Cinders are a type of volcanic material with low silica content, but are high in iron and magnesium. They form in eruptions that have discrete bursts of gases after magma comes into contact with water, similar to the way popcorn cooks. Their attractive red color is caused when the iron in the rocks becomes oxidized.
BONK – BONK -BONK!
Woah! Watch out for rock falls folks! These cinders have a shallow angle of repose, or angle at which loose material is most stable, of about 33 to 35 degrees. That means these rock falls can occur at any moment! The last time I came here, a small amount of material tumbled down the slope and caused a small dust cloud to stir into the air. The other tourists just watched it and continued sunbathing! Remember folks, its important to always be an aware tourist at locations like these so no one gets hurt! There’s a boat tour you can take from here to the white and black beaches all around the island! We’re going to another beach next!
Vlychada beach is our final beach today folks. It’s a black sand beach with large tan cliffs up to 30 m high.
The top part is composed of a tan ignimbrite deposited from the fourth phase of the Minoan eruption. An ignimbrite is made of deposits of a pyroclastic flow. The material here is tan because, during the upper part of phase 4 of the eruption, a protective rim was formed that surrounded the vent. This rim stopped sea water from entering the vent and lowering the temperature of the magma. This resulted in the tan color because of how hot the magma was when it erupted.
The pattern in the cliffs here was created from a type of weathering called taphony weathering. This occurs when large lithic fragments, which are the large boulders in the upper layer, fall out of the cliffs or finer material is taken away by the wind.
Watch out! Just like at Red Beach, these cliffs can be very unstable as the material also has a shallow angle of repose. This is evident from the talus, or rock fall, slopes that litter the brim of the cliffs. We’ll be stopped he for awhile as we wait for our bus to come pick us up. Feel free to try some Moussaka from a nearby restaurant down the boardwalk and enjoy some live music and dancing from the locals! Make sure to say kalispera (kah-lee-SPEH-rah), that means good afternoon!
Here we are at our last stop, the popular tourist town of Oia! Did you know that 2 million tourists visit Santorini annually to enjoy the view, drink the famous Santorini wine, get married or propose, partake in plays about Greek weddings, visit the volcano, and relax on the beaches (2). More than 850,000 arrive on boats and cruises, sometimes reaching up to 8 cruises docked here in one day since the amount of tourists who can visit is not limited (2)!Shop keepers use the volcano as a way to sell items to these tourists, including volcanic soaps, candles, jewelry, and even pumice and cinders!
Many of these tourists come to Oia to stay a few nights on the caldera rim. This can be extremely dangerous as the material along the edge of Oia can experience several faults where large blocks of rocks can slide down the slope of the rim. Oia is, in fact, the most unstable part of the island. It is built upon layer after layer of unconsolidated pyroclastic material that could be shaken up at any time by an earthquake.
Well folks, we’ve reached the end of our journey! I’d like to thank you all for accompanying me on a tour of this beautiful island that I’ve called my home for the last month. I’d like to send a special thank you out to my professor Lisa Skinner, who has taught me and my fellow colleagues the amazing geology of Santorini, and all of the friends I have made along the way!. Make sure to stay for the sunset folks so you can watch the last few golden rays of the sun branch out into the caldera! Just don’t get too close to the edge!
1. “Historic Eruptions of the Kameni Islands, Santorini.” Historic Eruptions – Santorini, University of Oxford, santorini.earth.ox.ac.uk/eruptions. Smith, Helena. “Santorini’s
2. “Popularity Soars but Locals Say It Has Hit Saturation Point.” The Guardian, Guardian News and Media, 28 Aug. 2017, http://www.theguardian.com/world/2017/aug/28/santorini-popularity-soars-but-locals-say-it-has-hit-saturation-point.