By: Tallulah Hutchinson, Maddie Mason, Molly Talbot

GPS Coordinates: 44.04625° N, – 123.07154° W

Google Earth link – Site 4

General Description and Location: 

This monument is located west of Deschutes Hall, outside the south entrance of the Lewis Integrative Science Building. The monument is a memorial for Wilson Pace Mays, and is made up of a slab of granite with a sundial on top. The sundial uses a gnomon, or protruding metal angle to cast a shadow on the plate of the dial, allowing the time to be read. The granite slab is rather large and flattened at the top to allow the sundial to rest evenly.

Geological Observations: 

The sundial is mounted on granite which we observed to be made of the following minerals: Feldspar, Quartz, Biotite, Muscovite. Due to the light color seen in Figure 1, it can be assumed that the rock is felsic and has a high amount of silica. We decided that it is an intrusive igneous rock with a moderate cooling speed, due to the presence of crystals between 0.5 and 2mm. The crystals are well sorted, both in size and type. The rock itself seems sturdy, though the sides appear weathered. The sundial itself has a diameter of ~60cm, as seen in Figure 2. The sundial is in an open field, where the entirety of the sun’s perceived movement across the sky can be observed. It’s important that the sun is unobstructed, so that the gnomon may cast shadows onto the dial. The building closest to the sundial is located to the north, which should not interfere with the usage of the sundial, as the sun rises in the east and sets in the west. The gnomon in the center of the sundial sticks out at an angle.

How Does Earth’s Rotation Contribute to how Sundials Work?

Contributed by Tallulah Hutchinson

 

 

 

 

 

 

 

 

 

Geological Question: Looking at this rock, one can’t help but notice the sundial on the top. It sticks out, literally and figuratively, with the angular gnomon protruding out of the metal plate below it. Looking at the sundial and observing the open area it’s been placed in, I wondered how the thing actually works. Sundials precede clocks as a time-telling device. Clearly you can read the time without understanding all the science behind how a sundial works, but what is that science? How Does Earth’s Rotation Contribute to how Sundials Work?

Description of Scientific Article: To begin answering my question, I found an article by Heierli (2019) about theoretically creating a sundial that has hour lines representing earth’s longitude and latitude lines (this will be defined later in my post). A sundial’s hour lines are the lines on the face that indicate each hour (figure 3). Although Heierli (2019)’s main theory is very complex and goes beyond my question, the beginning of this article provides some really good information about how sundials work.

Intersection with Article and Observations on Campus: One thing I noticed on campus was that the sundial had a plaque on the side with equations (figure 4). These equations indicate that the time the sundial shows will either be faster or slower than the time our clocks read depending on the month. This is because sundials display time according to solar time, rather than mean solar time, which is what our clocks use (Heierli, 2019 and references therein). Solar time is the time based on the sun’s observable position in the sky (Betts, 2023). When the sun is at its highest point, that is noon according to solar time. Heierli and references therein (2019) talks about how the length of days vary according to solar time by up to 1.3 seconds. This is because the earth orbits the sun at varying speeds. To avoid these inconsistencies, humans adopted mean solar time, a standardized version that averages the length of a true solar day (Betts, 2023). That’s why our sundial has equations for how fast or slow the sundial will read according to mean solar time. Also, I observed that the sundial’s gnomon (the shadow-casting device in the middle of the sundial) is angled (figure 1). Heierli (2019) notes that is typical of “classical” sundials like the one we have on campus.

An Answer to my Question? Heierli (2019) gave me the beginning of an answer to my question, which I was able to complete by finding other sources. For one, earth orbits the sun, which makes it appear like the sun is moving through the sky. When the sun is at its highest apparent point of the day, sundials read that the time is noon (Heierli, 2019 and references therein). This means that sundials only work because of earth’s orbit around the sun. Heierli (2019) and references therein also touched on how the hour lines that meet in the middle of a classical sundial (visible in figure 3, engraved as a sun). The place where these lines meet is a representation of earth’s celestial pole, or where the earth’s axis of rotation meets the sky. This seemed crucial to how sundials work, so I did some additional research. I found that since earth is tilted as it rotates, the gnomon of a sundial must be angled according to the latitude of its location (Salev, 2022). Latitude is an imaginary set of circles that run parallel to each other across the earth. A location’s latitude is measured by its distance from a celestial pole (IAU Office of Astronomy for Education, n.d.). The north and south poles are 90 degrees north and south respectively, and the equator (the middle of the globe) is 0 degrees. To properly intersect the sun’s path and cast an accurate shadow, a sundial on the equator would have a gnomon that sat flat against the plate of the dial, while a gnomon on the north or south poles would stick straight up. In Eugene, our latitude is around 44.0521 degrees north, so our gnomon is angled accordingly. All in all, Heierli (2019) had elements of how earth’s rotation contributes to how sundials work, which I used as a jumping off point to find more information.

Something Additional I learned and Future Questions: While the middle point of a classical sundial represents earth’s celestial pole, the hour lines that converge to form the point are not accurate portrayals of earth’s longitude lines (Heierli, 2019). Longitude means the circles that run perpendicular to latitude and represent a location’s degree to the east or west. Creating a sundial that accurately models the earth is challenging and is Heierli (2019)’s goal. In addition to successfully creating a prototype of an earth-modeling sundial, Heierli (2019) was able to include hour lines that represent the standard time our clocks are on, so conversion from apparent solar time isn’t necessary. This led me to wonder, could a model like this help scientists understand more about the sun’s path through the sky? Could that help us with issues like climate change?

Sources Cited: 

Heierli, J. (2019). A sundial with hour lines portraying the earth. American Journal of Physics, 87, 955-960. https://doi.org/10.1119/10.0000033

Betts, J. D. (2023). Solar Time. In Encyclopedia Brittanica Online. Retrieved from https://www.britannica.com/science/solar-time#ref144522

Salev, K. (2022). How Horizontal and Equatorial Sundials Work. Science of Gadgets. https://www.scienceofgadgets.com/post/how-horizontal-and-equatorial-sundials-work

IAU Office of Astronomy for Education. (n.d.). Glossary Term: Latitude. In The IAU OAE glossary. Retrieved December 3, 2025, from https://www.astro4edu.org/resources/glossary/term/171/

 

What physical and mineral properties of granite make it a suitable material for long-term use in outdoor monuments?

Contributed by: Maddie Mason 

Geological Question: While examining the sundial monument, I noticed how remarkably unaffected the granite base appears despite Oregon’s wet climate, as seen in the distinct edges of the granite in Figure 5, and despite the physical wear I would typically expect from decades of outdoor exposure. This made me curious about what specifically makes granite so effective as a material for monuments compared to other types of rock. This thought process led me to the question: What physical and mineral properties of granite make it a suitable material for long-term use in outdoor monuments? This is a geological question because the durability of a rock depends on its mineralogical composition, crystal structure, and the amount of empty space within the rock, known as porosity (University of Wisconsin–Madison, 2025). Understanding these properties helps explain how human-made structures interact with natural geologic processes over long periods of time. 

Scientific Article Chosen: To help me begin answering my question, I read an article by Hernandez et al. (2024) about the conservation state of Portuguese monuments. This peer-reviewed study examines several granite monuments in Portugal and evaluates how mineralogy, porosity, and environmental exposure influence their long-term preservation. I chose this article because it directly analyzes the weathering behavior of granite in outdoor structures, making Hernandez et al. (2024) an ideal source for understanding why the granite base of the sundial monument appears largely unweathered, as seen in Figure 5, while other monuments deteriorate more quickly. This study provides a scientific basis for connecting my observations of the sundial’s condition to broader patterns of granite preservation. 

Intersection Between Research and Observations on Campus: Hernandez et al. (2024) found that granite durability depends heavily on quartz abundance, low porosity, and tightly interlocking crystals. This means that granites with higher quartz content can resist chemical weathering because quartz is one of the hardest and least reactive common minerals. Hernandez et al. (2024) also emphasize that low-porosity granites rocks with less empty space between mineral grains absorb minimal water,, which reduces the risk of freeze–thaw fracturing during colder seasons and prevents long-term structural weakening. These findings match my observations of the sundial monument on campus. The granite’s visible quartz crystals and tightly packed mineral grains suggest a low-porosity structure similar to the granites described by Hernandez et al. (2024). When I looked closely at the edges of the monument, seen in Figure 5, I noticed that they lack sharpness and appear slightly rounded. If this rounding occurred naturally, it would align with Hernandez et al. (2024)’s explanation that feldspar minerals tend to weather first, even in otherwise durable granite. Since this granite contains feldspar, the slight surface deterioration is expected, and minor roughening over time is consistent with the weathering patterns described in the study. By comparing the study’s findings with the physical characteristics of the sundial monument, it becomes clear that the rock’s mineral composition and textural uniformity are major factors contributing to its long-term stability.

An Answer to the Question: My initial question was: What physical and mineral properties of granite make it a suitable material for long-term use in outdoor monuments? Hernandez et al. (2024) partially answered this question through their findings on the conservation of Portuguese granite monuments, which I compared with my own observations of the granite sundial on the University of Oregon’s campus. Hernandez et al. (2024) explain that a high quartz content gives granite significant hardness and strong resistance to chemical weathering. This is paired with low porosity, which limits water absorption and protects the rock from freeze–thaw damage. These traits are typical of stones that resist deterioration and therefore perform well in outdoor monuments. (Hernandez et al. 2024) The granite used for the sundial clearly displays these characteristics. Although there is some minor surface weathering, the monument remains structurally robust, demonstrating how its mineral properties support long-term durability. While the article helps support my conclusion, it does not fully answer my question. For example, although I now understand that quartz-rich granite is highly resistant, I still wonder why quartz is so resistant at the mineral level. I also want to know how granite forms with such low porosity and what controls that variability between different quarries. So my question was only partially answered: I gained a foundational understanding of why granite does not erode quickly, but I still have additional scientific questions to explore before fully understanding why this sundial monument remains so strong despite Oregon’s harsh weather. 

Something Additional I Learned, and Future Questions: One additional thing I learned from Hernandez et al. (2024) is that granite from different quarries can have dramatically different long-term stability, even when the rocks look similar at first glance. Small variations such as differences in grain size, mica content, or tiny microfractures can cause some granites to degrade much more quickly than others. Thinking about this discrepancy between seemingly similar granites made me wonder: How do architects evaluate which granite sources or quarries are most suitable for monuments,, and are durability tests performed before the stone is selected? Understanding how different granite sources are chosen could help reveal where architecture and geology intersect, especially when it comes to designing structures meant to last for decades or even centuries.

References

Hernandez, A. C., Sanjurjo-Sánchez, J., Alves, C., & Figueiredo, C. (2024). Study of the Geochemical Decay and Environmental Causes of Granite Stone Surfaces in the Built Heritage of Barbanza Peninsula (Galicia, NW Spain). Coatings (Basel), 14(2), 169. https://doi.org/10.3390/coatings14020169

University of Wisconsin-Madison. (2025). Understanding Porosity and Density – WGNHS – UW–Madison. WGNHS. Retrieved November 23, 2025, from https://home.wgnhs.wisc.edu/water/wisconsin-aquifers/understanding-porosity-density/

 

How does the silica content in an igneous rock affect its structural integrity and stability?

Contributed by Molly Talbot

 

Geological Question: How does the silica content in an igneous rock affect its structural integrity and stability?

When we first visited our site, we wanted to know what kind of rock we were looking at. Because of the coloring and crystal size (see Figure 6), we determined it to be an intrusive igneous rock, specifically granite. We decided that this granite, being so light, would be felsic, or high in silica. Considering the size and depth of the sundial, I wondered whether this silica content had anything to do with the strength of the rock, and its ability to hold the sundial over a span of many years. The sundial was made in memory of Wilson Pierre Mays, who passed away in 1910, so we can estimate that the monument is at least 100 years old. Though we can’t be sure whether the rock has been restored at any point in its history, or if it’s always been in that spot outside, we can see that this granite was a good choice for this particular monument.

Description of Scientific Article:

I selected Sousa (2013), an article comparing different granites used for building. I knew the article would address different features and benefits of each granite, along with a ranking for different aspects, so I figured I might be able to find an answer to my silica question. Sousa (2013) also addressed granites of different levels of weathering which was helpful for our specific monument, giving that it is outside and can be exposed to the elements as well as tactile interaction from passersby. Our granite is visibly somewhat weathered, but still uniform, and should be competitive in terms of strength.

Intersection between peer-reviewed research and observations on campus:

Sousa (2013) explains that rocks with larger grain sizes, or those that appear more heterogenous, meaning uniform, are likely to be less structurally sound, and are more likely to break or fracture. While our rock does contain visible crystals, they were only ~0.5mm-2mm across, so on the smaller side compared to some other granites we have seen, such as the slabs on the side of Columbia Hall. This would indicate that our rock is strong. Sousa (2013) also indicated that rocks with deeper fissures were less sound, which makes sense. The weathering on our rock appeared as just somewhat uneven surfaces, and small cracks here or there: nothing visibly deep. Finally, granites with higher uniaxial compressive strength are also more resistant to abrasions (Sousa, 2013 and references therein). A rock with uniaxial compressive strength is able to withstand much pressure without breaking. The fact that these rocks also resist abrasions shows that they are strong throughout the rock, both on the exposed surface and the hidden center or the rock. Our rock seems to fulfill this idea, not sustaining any large breakage or many abrasions, despite its place under this heavy, metal sundial for many years.

An answer to the question?:

Sousa (2013) did not directly answer my question. I was able to use the skills we learned in class to connect certain features of sound granites to the granite of our monument, but unfortunately, silica content was not one of the characteristics being studied. Our rock is both structurally sound and has a high silica content, but I was unable to determine whether the two were related. Based on Sousa (2013), silica content is not on the minds of builders using granite at this time. Grain size and porosity are more important to the strength of a granite.

Something additional I learned and future questions:

I learned that granite strength is also determined by when it was formed in relation to a tectonic event (Sousa, 2013). Post-tectonic granites, or those formed after a tectonic event such as plate subduction, tend to have better mechanical behavior, or resistance to breaking, especially uniaxial compressive strength (defined earlier). Sin-tectonic granites, on the other hand, were formed during the tectonic event, and are typically weaker. This was an interesting addition to my knowledge about the cooling and formation of igneous rocks, and I would like to know more. I am still curious to find out if silica content has any structural value to a rock, as in class we have only discussed it as a method of distinguishing the type of igneous rock. I wonder how similar testing to that in Sousa (2013) and references therein would work on igneous rocks besides granite, and perhaps even sedimentary or metamorphic rocks. Will granite continue to be a rock commonly used for building and monuments, or will others be found?

Sources Cited:

Sousa, L. M. O. (2014). Petrophysical properties and durability of granites employed as building stone: a comprehensive evaluation. Bulletin of Engineering Geology and the Environment, 73(2), 569–588. https://doi.org/10.1007/s10064-013-0553-9