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!
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) .
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.
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.
 Friedrich, Walter, L, 2009, Santorini: Denmark, Aarthus University Press, 312.