Arequipa: Part 1 – Volcanoes & Earthquakes

In late September, we arrived in Arequipa for the beginning of our 6-week stay in Peru. Jason, picked up a stomach bug on our travels from Costa Rica, so we wound up spending a few extra days letting him recuperate in this lovely city.

White City

Kids Room

Figure 1 – Our kids, Jamie & Jason, in our room at Casa de Sillar

Arequipa is called “The White City,” and it is easy to see why. Especially in the historic center, many of the buildings are built from white volcanic stone, or sillar. In fact, our hostel was a great example, as it was called the Casa de Sillar. As we’ll talk about later, volcanoes surround Arequipa. As there have been volcanic eruptions for millions of years, there’s a lot of sillar available for building.

The Plaza de Armas is the most impressive city central square we’ve seen so far. The square plaza is surrounded by sillar buildings, but is dominated by the Basilica Cathedral. The plaza looks very different at different times of the day and night because of the ways that light reflects off the white sillar.

Basilica Cathedral, Plaza de Armas

Figure 2 – Basilica Cathedral, Plaza de Armas

Plaza de Armas

Figure 3 – One side of the Plaza de Armas as the sun was setting

Basilica Cathedral at night

Figure 4 – Basilica Cathedral at night

Another highlight is the Monasterio de Santa Catalina. It was a functioning convent (a place where nuns live) for almost four hundred years, from 1580 until 1970. Since 1970 it has been open to the public as a tourist attraction. It takes up several blocks, and in fact has its own street system. Here are some pictures of the monastery from the outside and then from the inside, where the sillar is painted blue and red.

Monasterio de Santa Catalina

Arequipa is located at an elevation of 7,638 feet (2328 meters), so strenuous exercise immediately after arrival will leave you breathless. The reason this happens is that at higher altitudes there is a decrease in air pressure. This decrease makes it harder to get the same amount of oxygen into your blood. When you’re sitting around or walking in a flat area, most people don’t notice it. But if you try to run around or walk uphill quickly, you will get tired faster and feel like you’re out of breath. After a day or two, your body adjusts to the difference in air pressure. This is why when sports teams in the US play in a place like Denver (which is 5,280 feet or exactly one mile high), they like to get into town a few days before, so their players can get used to the difference in air pressure.

Unique Location – Volcanoes

Volcanoes, some of which are considered active, surround Arequipa. The most impressive one is El Misti at 19,101 feet (5822 meters), with its near-perfect cone visible from almost everywhere in the city. El Misti’s last eruption was in 1985.

Volcano El Misti

Unique Location – Earthquakes

Arequipa is seismically active, as is all of Peru. We were amazed to learn that there are an average of 200 earthquakes per year in Peru. This is quite new for us, as Minnesota, where we live, has no earthquakes. We were “lucky” to experience a small one (the first time our kids had felt one). Jason and I were in the hotel room, and when I told him the shaking we were feeling was an earthquake, his eyes almost popped out of his head. You get used to noticing the big green “S” in every building, which is the Security Zone, or the place you’re supposed to go in case of an earthquake.

Earthquakes SignThe reason there are so many earthquakes is that Peru is located near the intersection of two tectonic plates, called the Nazca and South American plates. Tectonic plates are huge pieces of rock that make up the outer layer of the earth, called the crust. They fit together kind of like a jigsaw puzzle.

Sometimes whole continents are on one piece of the jigsaw puzzle. However, these pieces don’t fit together perfectly. Sometimes they rub up against each other or one goes over the top of another. As the Nazca plate moves underneath the South American plate, earthquakes, and sometimes volcanoes, are created. In fact, this motion of the two plates is what has caused the rise of the Andes mountain range over many millions of years. Below is a diagram of the tectonic plates of the world. In the middle you can see the Nazca and South American plates.

In our next post we’ll talk more about Arequipa, what causes its very interesting weather, and the big challenge it faces in the future with water.

Costa Rica Map

Additional Links

Tectonic Plates definition on eHow
Wikipedia on plate tectonics

The tectonic plate image was found on Wikipedia and is in the public domain, courtesy of USGS

Study Questions:

  1. What is sillar?
  2. Why is Arequipa called “The White City?”
  3. True or False – If I live along the ocean and take a plane to Arequipa, get off, and right away run up a hill, I will feel more tired than if I did it along the beach?
  4. What are tectonic plates?
  5. What causes earthquakes in Arequipa (and Peru)?

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