Post by: Zach, Maddox, Jalen, and Barrett

GPS coordinates of campus feature:

+44.045647, -123.074276

Location on Google Earth (Site 1)

Figure 1 shows a close up on the fourth basalt piece from the left, with a 20 cm scale included (note the weathering in the lower portion). Figure 2 shows a wide angle view of the whole art piece, with both a 20 cm paper and 5’10” man for scale.

Location and general description: 

The campus feature is an art piece made entirely of basalt, wall-mounted on the South outside wall of Columbia Hall. The artwork is a collection of eight pieces of basalt, six make up the arch design on the left half of the artwork, while the other two pieces are outliers on the right half of the artwork. Created by sculpturist Steve Gillman, its primary purpose is for display and enjoyment by students and faculty alike.

Geological Observations: 

-The basalt pieces range in color, from a lighter grey to a darker greyish-black, indicating their mafic properties. 

-The basalt pieces have a varying range of textures, some smooth and some rough, while other pieces feature a mix of the two. The smooth areas appear artificially smooth, whereas the rough areas look more like natural rock.

-Very fine grained appearance, with little visible separation between different components, indicating the Basalt’s extrusive nature. 

-The artwork pieces are disc shaped, meaning they have long heights and widths, but thin lengths as the rock is very tightly compacted against the wall. The shapes of the discs vary from rock to rock, though they take roughly geometric shapes. The basalt pieces all have similar widths of between 20-25 cm, while the heights vary greatly between 20-90 cm. The lengths of all the rocks were 1-2 cm off of the wall.

 

There is some visible weathering on the basalt art piece, does basalt weather quickly, and is this property influenced more by its mafic or extrusive nature?

Contributed by Zach Matlock

Geological Question: I picked my question based on my interest in the hardness of rocks. I have always thought it fascinating that rocks, which all feel hard to me, exist on a scale (the Mohs Hardness Scale) with some being considerably harder than others. This pushed me to choose the question: does basalt weather quickly, and is this property influenced more by its mafic or extrusive nature? I am hoping that through my investigation, I learn if hardness is a major factor in physical weathering, and if basalt is considered a hard or soft rock. I am also quite curious which characteristics of basalt are due to it coming from mafic magma (less silica rich, darker rocks formed), and which characteristics come from its classification as extrusive (formed/cooled above the crust of the planet). There are numerous things that influence the nature of basalt, and all of them likely influence the weathering visible on the sculpture, such as on the left side of figure 1. 

Description of scientific article: I chose to read Dursun and Topal (2019) because it has extensive field observations analyzing the weathering of basalt city walls in Turkey. The article is attempting to look at the deterioration mechanisms on basalt, and I am hoping in its investigation it answers my geological question. In the analysis of the city walls, it would seem prudent to at least discuss the mafic, extrusive nature of basalt. These could be the lenses through which the rate of weathering is looked at, and if that is the case my question will surely be answered. Either way, the content of the article could not be any more relevant to the topic of basalt weathering, and that’s why I have chosen it for this purpose.

Intersection between peer-reviewed research and observations on campus: Dursun and Topal (2019) notes that basalt is fine grained, and when it gets weathered it becomes pale brown, yellowish, or even red. The basalt on the campus feature is incredibly fine grained as well, visible in figure 1, which is a testament to the fact it cooled quickly outside of the crust before crystals had time to form. The off color weathering noted in the article is not really seen on the sculpture though, indicating the art piece is not near as old as the Turkish basalt observed. The article also noted that they recommend basalt as a building material due to its ability to withstand physical stressors, and its resistance to common weathering vehicles such as a wetting-drying cycle (Dursun & Topal, 2019). This too aligns with our field observations, the cracks visible in the rock are so narrow they appear almost smooth, and there are no deep indents or missing chunks. Resistance to wetting and drying are critical in areas of high precipitation like Oregon, and the Columbia hall basalt displays this utility well. Though the basalt discussed in the article is much older and more weathered than the campus feature basalt, the conclusions the authors are able to draw consistently correspond with the observations made on the younger art display.

An answer to the question? The scientific article partially answered my question, it was very helpful in analyzing how things (specifically basalt) weather, but it was unhelpful in determining whether this was due to it being extrusive or Mafic. This is primarily because it never discussed those characteristics of basalt, it was only analyzing basalt so it had to reason to categorize it. It went very in-depth on weathering in basalt, but a more helpful article might have compared basalt to a different rock and investigated why one weathers faster than the other. That being said, it described various features of basalt that contribute to it being able to withstand physical degradation, which answers the first part of my question. I now know basalt weathers slowly, and can hypothesize that the broken area in figure 1 may actually be due to the sculpting process. 

Something additional I learned and future questions: One additional thing I learned is that pore size of rocks directly correlates with the rate at which they weather, and basalt has pores larger than 5 micrometers which protects it to some extent (Dursun & Topal, 2019). The reason pore size is relevant is because the pores of a rock, tiny holes that penetrate the surface, allow water to drain from the rock. When the pores are too small, anything smaller than 5 micrometers, the water gets trapped inside and can freeze. When it freezes it expands, and that is when weathering can occur. Over time the ice breaks down the rock from the inside out. This does make me wonder though, is pore size at all relevant if temperatures do not get below freezing? Can other small particles enter through larger pores and corrode away rocks by that method?

 

What are the distinctive characteristics of flood basalts, and how do they form in comparison to other basaltic lava types?

Contributed by Maddox Morris

Geological Question: Basalt is one of the most common rocks in the world, but not all basalts are the same. Flood basalts are interesting because they form from massive volcanic eruptions that cover vast areas with thick layers of lava. A flood basalt is a type of basaltic lava flow that erupts rapidly and covers a wide area. Understanding the formation of flood basalts can give insight into past mass extinctions and volcanic activity. This makes me wonder: What are the distinctive characteristics of flood basalts, and how do they form in comparison to other basaltic lava types? This question is related to geology because it explores the formation of different lava types and provides further insight into Earth’s volcanic history.  

Scientific Article Chosen: To help me start answering this question, I read about basaltic volcanic systems in an article by Walker (1993). In this article, Walker (1993) examines the formation and characteristics of different basaltic lava types, including flood basalts. I chose this article because it analyzes how flood basalts differ from other basaltic lava flows in terms of eruption style, composition, and geological impact.  

Intersection Between Research and Observations on Campus: Walker (1993) explains that basaltic lava cools rapidly at the surface, which creates a fine-grained, dark-colored rock with small, visible minerals. This aligns with my observations of the basalt on campus, which is fine-grained and grey/black (Figure 1). Walker (1993) also explains that basalt can have a variety of textures depending on its formation process. Some basalt surfaces remain rough while others are smooth because of natural weathering or artificial modification. The basalt I observed demonstrated this, with some areas being naturally rough while others were smooth and polished. Additionally, Walker (1993) states that basalt often forms in extensive flows, yet can be shaped when used in human-made structures. The arrangement of basalt on campus (Figure 2) demonstrates this because the rock’s natural characteristics are preserved while it is built into a constructed setting.  

An Answer to the Question? My initial question was: What are the distinctive characteristics of flood basalts, and how do they form in comparison to other basaltic lava types? This article partially answered my question by explaining how flood basalts differ from other basaltic lava types in terms of eruption scale, magma supply, and geological impact (Walker, 1993). Walker (1993) describes how flood basalts erupt from scattered vents and produce thick lava flows that stack over time, distinguishing them from shield volcano eruptions, which erupt from one centralized volcano. However, the article did not talk about some specific differences between basaltic lava types such as cooling patterns or mineral composition. I now have a better understanding of the characteristics and formation of flood basalts, but I am still curious about specific cooling and crystallization differences between flood basalts and other basaltic lava types.  

Something Additional I Learned and Future Questions: Additionally, one of the most interesting things I learned from Walker (1993) is that flood basalt eruptions do not occur as a single event but as a series of massive lava flows over millions of years. Some of the largest flood basalt areas, like the Deccan Traps, were built up in multiple phases. The eruptions happened in pulses rather than as a continuous outpouring of lava (Walker, 1993). This helped me understand that these events are not just catastrophic eruptions but very long processes. However, Walker (1993) does not fully explain what controls the timing of these eruption pulses. This makes me wonder: What geological factors determine the pauses and resumptions in flood basalt eruptions over time? 

 

Based on the features from the basalt sculpture at Columbia Hall, can we determine whether it’s continental basalt or oceanic basalt? 

Contributed by Jalen Wang

Geological Question: If you’ve ever walked past Columbia Hall, you might have noticed a sculpture mounted on the south wall. When looking at it, it may seem like just a random rock sitting on a wall, but a further examination reveals that the sculpture is all basalt—one of the most common volcanic rocks on Earth. Seeing this got me thinking: Can we determine whether the basalt used in this sculpture is from an oceanic or continental source? Basalt forms in both oceanic and continental environments. This post will be focused on attempting to determine whether or not the basalt is oceanic or continental solely based on visual aspects as we cannot perform a chemical analysis. Differentiating between the two based on visual characteristics alone can be tricky. Oceanic basalt, typically formed at mid-ocean ridges, tends to be fine-grained, dark-colored, and iron-rich, while continental basalt, often associated with large volcanic provinces, can exhibit more varied textures and compositions. The sculpture’s basalt pieces display a fine-grained texture, mafic coloration, and a mix of smooth and rough surfaces, but do these features provide enough evidence to confidently classify it?

Description of scientific article: To help me start answering this question, I read about subaerial lava flow morphologies in an article by Tracy K.P. Gregg (2017). The article discusses how different basaltic lava flows solidify and the factors that influence their final morphology. I chose this article because Gregg (2017) discusses how texture, structure, and cooling processes shape the basalt’s appearance, which is relevant to determining whether visual characteristics alone can indicate whether a basalt is oceanic or continental. I think this article will help me answer my geological question because it provides important information into how basalt’s visual features develop and whether those features are tied to a specific geologic setting such as oceanic or continental. By understanding the role of factors like cooling rate, eruption environment, and flow dynamics, I can determine whether the basalt on the Columbia Hall wall exhibits characteristics that support it being either an oceanic or continental origin.

Intersection between peer-reviewed research and observations on campus:
Gregg (2017) describes how lava flow morphology is shaped by factors like cooling rate, and eruption conditions, many of which overlap with my observations of the basalt sculpture at Columbia Hall. One of the key takeaways from the article is that fine-grained textures in basalt indicate rapid cooling, which is common in both oceanic and continental basalt. The basalt in the sculpture has a very fine-grained appearance, supporting the idea that it cooled quickly, which means it’s most likely an extrusive igneous rock. However, this characteristic alone does not definitively tell us whether or not the basalt is attributed to an oceanic or continental source. In addition, another similarity between the research and the sculpture is the varying surface textures. Gregg (2017) explains that basalt can develop smooth or rough textures, which is determined by the viscosity of the lava and the cooling environment. The sculpture’s basalt is both smooth and rough, which could mean different cooling histories. This directly relates to how lava flows solidify in the real world. There are areas that cool quickly and remain smooth, while other areas are more disrupted by gas content or flow conditions, which ultimately leads to a rougher texture.

An answer to the question? My initial question was: Can we determine whether the basalt used in the Columbia Hall sculpture is from an oceanic or continental source based on visual characteristics alone? This article partially answered my question by explaining how basaltic lava flow morphologies develop and what factors influence their appearance. The information and discussion of fine-grained textures, smooth surfaces, rough surfaces, and different lava flow types provided valuable information into how basalt solidifies in different environments (Gregg, 2017). However, while these visual characteristics can certainly help us get closer to determining a possible origin, they do not give us a definitive answer as to if the basalt is oceanic and continental. A geochemical analysis would have been the most efficient way to determine whether the basalt was oceanic or continental.

Something additional I learned and future questions: One of the most interesting things I learned from this article is how lava tubes form and change over time. Gregg (2017) explains that lava tubes can form under pahoehoe flows when lava keeps moving beneath a hardened surface. These tubes help lava travel long distances without cooling too quickly, which explains how some lava flows can stretch for hundreds of kilometers. Gregg (2017) also points out that once a lava channel forms, it takes a big change in lava speed or amount to shift into a different type of flow. This made me wonder: How do different planets, like Mars or Venus, affect how lava tubes form and last over time compared to Earth?

 

Where did the basalt in the artwork likely come from, and how does that help us learn the age, type of basalt, and other descriptive aspects of it?

Contributed by Barrett Fedderly

Geological Question: Have you ever wondered if local artwork is made from materials near to you? An artist making art out of local materials can be a really strong way to form an emotional bond between the art and the viewer. Many pieces of art on UOs campus have become staples of the community, and so I was interested if the basalt represented Oregon in more than just where the finished artwork is located. My initial question was: where did the basalt in the artwork likely come from, and how does that help us learn the age, type of basalt, and other descriptive aspects of it? The information discovered from the question could help UO students develop a deeper personal connection to this art, as it represents the local Oregon area as well.

Description of scientific article: I chose the article, Cahoon et al. (2020), as it delves into the time period of the Columbia River Gorge Basalt (CRGB) creation, and re-answers questions with new discoveries. Cahoon et al. (2020) revisits the timeline of one of the key volcanic formations within the CRBG: the Picture Gorge Basalt. Originally considered a relatively short-lived eruption phase, this formation is now understood to be both the earliest and longest-erupting unit of the CRBG. I believe the question will be investigated and answered by Cahoon et al. (2020), as the article made new discoveries about the time period the basalt is from. The age paired with the cause of creation gives a largely clear idea of what the basalt is and other defining aspects of the rock.

Intersection between peer-reviewed research and observations on campus: The basalt in the campus art piece has no description of where the basalt rock is from, however due to basalt being extremely dense and heavy, it makes the most sense for the material to come from a location close to the resting place of the art. Cahoon et al. (2020) states that the basalt of the CRGB formed between 5-17 million years ago, during the Miocene Epoch. The Miocene Epoch was the period of time roughly 5-23 million years ago, and was generally characterized by warmer climates, the expansion of grasslands, and the evolution of many modern mammal species. Additionally, due to the long lived eruptive system that created basalt during the course of over 12 million years, the basalt is created of many different elements and mixtures of materials. The CRGB spans across Washington, Oregon, Idaho, and Nevada, and is one of the largest flood basalt provinces in the world. Due to the scale of the CRGB, the basalt may not originate from the local Oregon area, but with a sample test to find the elements within the artworks basalt, it can be tested to see if similar elements are found within local Oregon basalt. Basalt often forms hexagonal columns as the lava cools into rock, and this aspect has become a famous visual staple of the exposed basalt within the Columbia River Gorge. Unless the rock has been altered by the artist, this can be seen in Figure 2 where the rocks look to have sharp edges and are polygonal shapes, possibly representing the shape of columns within the CRGB.

An answer to the question? My initial question was where did the basalt in the artwork likely come from, and how does that help us learn the age, type of basalt, and other descriptive aspects of it, and the article largely helped me answer it. There are a few aspects that are vague, however not at the fault of the article. The basalt has not been sampled, so there is no way to completely claim where it originated from. However, using logic I was able to hypothesize an estimated location, and then find descriptive information. Cahoon et al. (2020) provided the age and visual appearance of the basalt, along with the description of differing elemental structures along the hypothesized area. All of these details allowed me to create a very proficient guess on the specific aspects within the basalt artwork.

Something additional I learned and future questions: The article, Cahoon et al. (2020) helped me to learn additional information I was not aware of in relation to the CRGB. The scale of the flood basalt province clarifies that CRBG eruptions weren’t as tightly clustered in time as once thought, suggesting a more prolonged and complex volcanic history within the region. A question I have after investigating the article is: What drove the early and prolonged volcanism in the Picture Gorge area? The Picture Gorge Basalt was the early eruption of the CRGB, and understanding the cause of it could help to piece together the reason for other areas of the CRGB.

 

Works Cited:

Cahoon, E. B., Streck, M. J., Koppers, A. A., & Miggins, D. P. (2020). Reshuffling the Columbia River Basalt chronology—Picture Gorge Basalt, the earliest-and longest-erupting formation. Geology, 48(4), 348-352.

Dursun, F., & Topal, T. (2019). Durability assessment of the basalts used in the Diyarbakır City Walls, Turkey. Environmental Earth Sciences, 78, 1-24.

Gregg, T. K. (2017). Patterns and processes: Subaerial lava flow morphologies: A review. Journal of Volcanology and Geothermal Research, 342, 3-12.

Walker, G. P. (1993). Basaltic-volcano systems. Geological Society, London, Special Publications, 76(1), 3-38.