June 6, 2018
Today we went on an amazing hike from the base of Peresteria volcano to the city of Οια (ee-Yah) in Santorini, Greece to broaden our knowledge on volcanic formations. We arrived on the outskirts of Οια approximately at 11:03 a.m., which was early enough to experience a light breeze from the north. Personally, I was super tired from hike down to Cape Plaka yesterday. The hike was intense, the sun beat hard, and I got beat up by the ocean pretty bad. Sweat burned in the cuts and scratches on my leg and hand. Additionally, had I known that the hike would be so strenuous would have definitely worked out before flying over to Santorini. Honestly, someone should have warned a big girl like me. Despite all the stress of hiking the class came across some interesting formations along the way.
We stopped off to the side of the road and discussed the geology of where we were standing. We saw that Peresteria Volcano is under Megalo Vouno and two cinder cones. I thought this was interesting because the color difference in the rocks was noticeable and parts of the volcanos are still visible. Then, before we officially began our hike, we saw a horst and graben near the base of Peresteria Volcano. This was important for us to identify because it implies there are two normal faults running along this section; one fault known as the Colombo Line is active. What makes it a risky place is that there is a villa known as the Architects’ House resting on this formation. Any earthquake or movement of the fault and those staying there are doomed to tragedy. My feeling on this was of surprise on how some people blindly stay in places that could be potentially hazardous. Ignorance is bliss, but knowing about the surrounding areas is better.
On the trail, after trecking up one of two cinder cones we came across a dike. A dike is formed when there are vertical cracks from the magma chamber to the surface. Magma then makes its way up though the cracks and ooze out to the surrounding surface. I was simply bamboozled. At first I found it difficult to actually believe it was a dike because it was covered in red cinders. All around us on the the trail were black cinders, not a red one in sight. The thought of a dike oxidizing the surrounding cinders with its heat, making them red, did not cross my mind at first. That and I was simply out of breath; it was difficult trying to advance uphill on the loose cinders. This, however, is not the only dike on Santorini. We were informed that there are more than 120 dikes on the island.
Xenoliths in flow-banded basalts are another formation we came across. Further uphill from the dike we saw two boulders on the edge of the trail. Any strong push and anyone under the boulders could get squished. Other than their positioning the boulders had noticeable xenoliths and flow-banding. The flow-banding is created by the shearing and smearing of lavas. Hot lavas pass on top of cooled lavas and create “layers” on top of cooled layers. The flow-banding lavas will sometimes go around rocks of some outside source, xenoliths, and kind of push them around and flow over their long side. The xenoliths don’t melt because they are cooler than the surrounding lavas. This leaves them preserved in the basalt.
After hiking and sweating a lot we reached our last point of interest with the class. We were located on top of one of the two cinder cones on top of Megalo Vouno which has purple looking scoria over it, suggesting high temperatures. The view looked over Οια, some farm, the sea, and Skaros and Peresteria. We were presented the area where Peresteria ends and Skaros begins. This was significant because we noticed that Skaros formed after Peresteria because Skaros is built up against (Skaros is a shield volcano) and flows over some parts of Peresteria.
The hike was a success in allowing the class to identify volcanic formations. We finished up class and took pictures by another dike that was nearby and set out for Οια. The city was lively and full of people from all over the place. A donkey tour group passed us by on our way to look for a bookstore called Atlantis Books. The day passed us by in a flash while we were there. I guess this always happens when I start having fun. Oh well. I hope that our next hike is just as action packed as this one! Until next time my sweet diary!