Week 3 video questions

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University of Oregon *

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Geology

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Apr 3, 2024

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docx

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Uploaded by SuperHumanBarracuda3779

Questions on Where Terranes Collide: The Geology of Western Canada 1. What were the origins of the rocks composing the Intramontane Superterrane? They're made out of the broken shells of marine organisms. Above the limestones, the rocks are called marine lavas that have poured across the limestone banks and built a volcanic pile. 2. How many terranes were amalgamated (joined together) into the Intramontane Superterrane? Four terranes, the Stikinia, Quesnellia, Slide Mountain, and Cache Creek 3. What is a melange rock, and where do they typically originate? A combination of limestone, chert, basalt, and more all mushed together into one rock. They were originally on the floor of the ancient Cache Creek ocean. 4. What happened to the rocks forming the edge of the continent as they collided with the continent? The rocks were compressed, deformed, and melted forming rocks called the Omineca Belt Questions on Regional Alaskan Tectonics 1. The distance between the trench (marking the boundary between the subducting oceanic plate and the overriding continental plate) and the volcanic arc (produced by partial melting of the mantle wedge above the descending slab) varies from one end of the Aleutian volcanic arc to the other. What determines this distance? The angle of plate subduction determines the distance between the trench and the volcanic arc. Additionally, changing rates and directions. 2. In the 2002 M 7.9 Denali Fault Earthquake, how much slip (displacement) occurred along the fault, and how far away were the effects felt? It produces up to 8 meters of right lateral displacement. It triggered small earthquakes up to 3600 km away. Questions on In the Path of a Killer Volcano : 1. In the predictions of the 1980 Mount St Helens eruption, what did volcanologists get right, and what did they get wrong? They successfully predicted the time of the eruption but did not predict the size or the lateral direction of the eruption. 2. Who first noticed the renewed activity of the Philippine volcano? Ray Punongbayan 3. What are the three possible explanations for earthquakes beneath a volcano?

Magma rises, releasing excess gas, or tectonic stresses. 4. On the flight to the Philippines, USGS volcanologists passed over Katmai Volcano, Alaska, which erupted in 1912. Why was this relevant to Mt Pinatubo? They both look similar to each other, both have ash-flow sheets and pyroclastic flows around the area. 5. What did carbon dating of incinerated trees reveal about the eruptive history of Pinatubo? They indicate that the mountain has erupted only about 4 or 5 times in the last 2000 years. 6. What are three primary methods of monitoring a possibly threatening volcano to predict whether or not it will erupt ? Correlation spectrometer, seismographs, and visual monitoring. 7. Which of these methods tells you if magma is moving beneath the volcano? Spectrometer 8. Which method tells you if the volcano is plugged and may be nearing eruption? Seismographs 9. What is a pyroclastic flow ? What is a typical temperature and speed of a pyroclastic flow? Hot dense avalanches of ash, lava fragments, and gases typically reach up to 700 degrees Celsius and flow at 60 miles per hour. 10. What is a lahar ? Super destructive mudflow 11. Geological interpretations have consequences. The film refers to two other significant failures to accurately predict volcanic activity. What were they, and how do they illustrate the issues facing volcanologists in this situation? If volcanologists determine there is no threat of an eruption, but an eruption occurs, thousands of people can be killed because of it. However, when their predictions are right but don't get the notice out in time, many people die. 12. What did the spine or dome of fresh magma indicate? Explosive magma 13. How many people died in the actual eruption? How many were successfully evacuated? 43 died, 120,000 evacuated 14. How does this eruption compare in volume to St Helens in 1980? It was ~10 times bigger than the MT. St. Helen’s eruption. 15. How long after the evacuation did the volcano erupt? ~48 hours after the evacuation

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