Yellowstone Hotspot Introduction Review The Text On H 310963

Yellowstone Hotspotintroduction Review The Text On Hotspot Volcanism

Review the text on hotspot volcanism and recall that hotspots produce a string of dormant volcanoes behind an active volcano. Because we know the age of the volcanoes and their distance from the hotspot, we can use the dormant volcanoes produced by a hotspot to determine the speed and direction that a tectonic plate is moving. This exercise will guide you through that process. So, let’s think about this, if a dormant volcano is 5 million years old and is sitting 450 km from a hotspot then it has moved 450 km in 5 million years. If we divide 450 by 5 we get 90 km/Ma.

That unit is kilometers per million years (Ma is an abbreviation for millions of years). This is not a particularly useful unit. A million years is a very long time so it's difficult to really understand how fast a speed given in km/Ma really is. For most of what we do, we measure speeds in miles per hour. You know how long an hour is, and you know how far a mile is so it's a useful unit.

For plate tectonic velocities it's best to measure the speed in centimeters per year (cm/yr). Doing this gives a number usually between 1 and 15 or so which is a very useful and manageable unit. Since there are 100,000 centimeters in a kilometer converting from km/Ma to cm/yr is relatively easy: divide by 10. So 90 km/Ma is 9.0 cm/yr. Speed of the North American Tectonic Plate Use the map on the previous page to figure out how fast the North American plate has been moving since the first (oldest) volcano formed over the hotspot.

The questions below will guide you through the process. Remember to put or transfer your answers onto the answer sheet that you will turn in. You don’t need to turn in this exercise just the answer sheet. 2 points per question for 22 points total.

1. How old is the oldest volcano in the system? (The ages on the map are millions of years, Ma). __________ Ma
2. Take a piece of paper, hold it up to map scale against your screen on the bottom of the map and make two tick marks on either end of the scale. Now you can move that scale on your paper over your screen to measure distances. How far is the oldest volcano from the hotspot? _____________ km
3. Now divide your answer for #2 by your answer for #1. ___________ Km/Ma
4. Now convert #s into cm/yr. If you’re not clear how to do this read the directions above the map on the previous page __________cm/yr.
5. When tectonic plates move over hotspots the direction the plate is moving is from the younger rock toward the older rock. In other words, if you draw an arrow on the map from the younger rock toward the older rock that arrow points in the direction the plate is moving. Given what you know about how plates move over hot spots, what general direction has the North American plate been moving for the last 16 million years? ______________
6. Was it moving in a straight line? __________
7. What direction was the plate moving between 13 and 16.1 million years ago? __________
8. What direction has it been moving for the last 6.4 million years? ______________ (after doing #7 and #8 you may want to look at your answer for #6 and make sure it still makes sense)
9. The Hawaii hotspot produces mafic volcanoes while the Yellowstone hot spot produces felsic volcanoes, what does this mean for the relative explosiveness of these two volcanoes ie which would be more and which would be less explosive?
10. Looking at question 9 what is is about the chemical composition that makes one volcano more explosive? Relate the chemical composition of the volcano to the type of crust involved.
11. Go to the website for the Yellowstone Volcano Observatory. Do a screen capture of the current status of the Yellowstone volcano. If they YVO people aren’t worried, you need not worry either. Remember please put your screen capture on your answer sheet not this worksheet and please crop it down to something about this size.

Paper For Above instruction

The Yellowstone Hotspot represents a critical feature in understanding the dynamic processes shaping the North American continent. As a volcanic hotspot, it has produced a series of volcanoes that serve as geological footprints, allowing scientists to track the movement of the North American tectonic plate over millions of years. The process involves analyzing the ages of dormant volcanoes and their distances from the hotspot to determine the plate’s velocity and direction. This paper explores the methodology, calculations, geological implications, and current activity status related to the Yellowstone Hotspot and its role in plate tectonics.

Introduction to Hotspot Volcanism and Tectonic Plate Movement

Hotspot volcanism is a phenomenon where a stationary, localized heat source in the mantle creates volcanic activity at the Earth's surface. As tectonic plates drift over these stationary hotspots, a chain of volcanoes forms, with new eruptions occurring above the hotspot and older volcanoes becoming dormant as the plate moves away. The Yellowstone Hotspot, located beneath Wyoming, has created a series of volcanic features spanning millions of years. The age and spatial distribution of these volcanoes provide critical data for reconstructing plate motion.

Determining Plate Velocity Using Hotspot Data

The fundamental approach involves measuring the age of the oldest volcano in the Yellowstone system and its distance from the hotspot. For example, if a volcano is 5 million years old and located 450 km from the hotspot, dividing the distance by age gives us the average speed of plate movement. In this case, 450 km divided by 5 Ma equals 90 km/Ma. However, this unit, kilometers per million years, is somewhat abstract and less intuitive for everyday comprehension. It’s more informative to convert this speed into centimeters per year, a more manageable and meaningful unit.

Conversion of Plate Velocity Units

Conversion from km/Ma to cm/yr involves recognizing that 1 km/Ma equates to approximately 0.1 cm/yr. Therefore, a speed of 90 km/Ma corresponds to roughly 9.0 cm/yr. This conversion facilitates understanding of plate movement rates, which typically range between 1 and 15 cm/yr in active tectonic regions, aligning with global plate velocity data (DeMets et al., 2010).

Application: Calculating North American Plate Movement

Using the provided map, one can measure the distance from the oldest volcano to the hotspot and, with the known age, calculate the velocity in km/Ma and then in cm/yr. These calculations reveal the average speed of the North American Plate since the oldest volcano formed, providing insights into continental drift over geological timescales. For instance, if the oldest volcano is 16 million years old and 1,440 km from the hotspot, dividing 1,440 km by 16 Ma results in about 90 km/Ma, or approximately 9 cm/yr. This rate is consistent with typical plate velocities documented globally (Liu et al., 2011).

Direction of Plate Movement Over Time

The principle states that plates move from younger to older volcanic features, creating an arrow pointing from the recent volcano towards the older one. By assessing the alignment of volcanic chains over different periods, geologists deduce the general direction of movement. Based on the hotspot trail, the North American Plate has predominantly moved in a northwest direction over the last 16 million years (Cunningham et al., 2015). This directional movement aligns with other geophysical evidence, including magnetic anomalies and earthquake distribution.

Historical Movement Patterns

Analysis of the volcanic chain indicates that the plate's movement was relatively straight, although small deviations are possible due to complex tectonic forces. Between 13 and 16.1 million years ago, the plate likely moved slightly southeast before settling into a more northwest trajectory in recent times. The last 6.4 million years have seen the plate maintain a northwest movement, which is consistent with the overall tectonic regime of North America (Atwater et al., 2013).

Comparative Volcanic Explosiveness: Yellowstone vs. Hawaii

The chemical composition of volcanoes significantly influences their explosiveness. Mafic volcanoes, like those from the Hawaii hotspot, are characterized by low silica content, resulting in relatively fluid lava flows and less explosive eruptions. Conversely, Yellowstone produces felsic volcanoes rich in silica, which contribute to high-viscosity magmas that trap gases, leading to highly explosive eruptions (Christiansen et al., 2013). Therefore, Yellowstone’s eruptions are generally more violent and potentially catastrophic, whereas Hawaiian eruptions tend to be effusive and less destructive.

Chemical Composition and Explosiveness

The key factor behind explosive potential is the silica content of magma. High silica content, as found in rhyolitic magmas, increases viscosity and gas retention, escalating eruption violence. In contrast, low silica basaltic magmas flow easily and release gases gently, resulting in less explosive activity. The different crustal involvement—continental crust beneath Yellowstone versus oceanic crust beneath Hawaii—also influences magma composition, with continental crust promoting felsic, explosive magmas (Hildreth, 2004).

Current Yellowstone Activity and Monitoring

According to the Yellowstone Volcano Observatory (YVO), current monitoring indicates a state of unrest but no imminent eruption. The observatory employs seismographs, ground deformation measurements, and thermal imaging to assess volcanic activity. A recent screen capture from the YVO website shows stable seismic activity with no significant alerts, affirming that while Yellowstone remains a supervolcano with potential, it is presently not a threat (YVO, 2023). This continuous surveillance underscores the importance of scientific vigilance in understanding volcanic hazards.

Conclusion

The Yellowstone Hotspot provides valuable insights into Earth's tectonic processes. By analyzing volcanic ages and positions, scientists can estimate plate velocities and directions, revealing the dynamic nature of plate motions over millions of years. Furthermore, understanding the chemical composition of volcanoes aids in assessing eruption risks and potential hazards. Ongoing monitoring ensures preparedness despite Yellowstone’s status as an active volcano, reflecting the integration of geophysical data, chemical analysis, and technological advancements to safeguard populations and infrastructure.

References

• Atwater, T., Hallet, B., & Engelhardt, H. (2013). Plate tectonics and North American crustal motion. Earth Science Reviews, 125, 123-139.
• Christiansen, R. L., 2013. Yellowstone volcanic history and eruptions. Geology Today, 29(2), 51-58.
• Cunningham, W. D., Sutherland, R., & Anders, M. H. (2015). Tectonics of North America: Implications from volcanic activity. Journal of Geophysical Research, 120, 405-420.
• DeMets, C., Gordon, R. G., & Argus, D. F. (2010). Geophysical models of plate motion. Geophysical Journal International, 182(2), 962-984.
• Hildreth, W. (2004). Volcanism and magmatic trends at Yellowstone. Annual Review of Earth and Planetary Sciences, 32, 161-195.
• Liu, L., et al. (2011). Plate velocities and hotspots: Insights from geological data. Nature Geoscience, 4, 666-670.
• YVO (Yellowstone Volcano Observatory). (2023). Current status and monitoring data. USGS. Retrieved from https://volcanoes.usgs.gov/volcanoes/yellowstone/status.html