Activity 2: Tuff Tuff is a rock made from primarily volcanic ash. The ash is com
ID: 118356 • Letter: A
Question
Activity 2: Tuff Tuff is a rock made from primarily volcanic ash. The ash is compacted through the process of consolidation, and forms a solid rock. Tuffs can form from ash deposited in pyroclastic flows, or as ash fall from the air 2.1. The picture below shows a rhyolitic tuff, with ash fragments (in red) surrounding a larger piece of tephra: If an ash is deposited fast enough and with enough volume, it can retain much of the heat of the eruption. Such ash can fuse together under its own heat to form a welded tuff. Would that ash be brittle or ductile? Does the ash in the image appear to be brittle or ductile, and why? 2.2 Do you think this ash formed close to the volcano or far away from it, and why? Do you think it formed out of ash from a pyroclastic flow, or air fall?Explanation / Answer
2.1 – Would that Ash be Brittle or Ductile? Does the ash in the image appear Brittle or Ductile? Why?
Answer - The ash would be brittle. This is because, after consolidation, it will lose its heat and form a solid mass. This mass under application of external stress will not bend but break, hence showing characteristics of brittleness.
The ash in the image, however, appears ductile. This is because while consolidating, the ash was hot and was welding together to form a welded tuff. The flow structures were formed during recrystallization of molten tuff. This tuff was derived from a pyroclastic flow. Hence it shows flow structures.
2.2 – Do you think this ash formed close to the Volcano? Is it from a pyroclastic flow or ash fall?
Answer - Yes it formed close to the Volcano. It is from a Pyroclastic flow.
Why?
Because pyroclastic flows are mostly observed on the flanks of the volcanoes.
2.3 Tuff is from Ash or Pyroclastic flow? Was it formed closerr or away from the Volcano?
Answer - Izushima Tuff shows a layering structure. Pyroclastic flows seldom form such well differentiated stratified structures. On the other hand tuffs falling from the air do form such layering. The izu shima image is the compilation of several eruptions and the consequent ash fall in a single photograph. Hence this Tuff is from Ash fall and not from a Pyroclastic flow.
This structure could have been formed away from the volcano as ash is carried far away in the atmosphere due to prevailing winds.
2.4 Would you consider Tuff to be an Igneous or Sedimentary rock? Provide your reasoning
Answer - Tuff show sedimentary characters like showing stratification, association of various detrital and clastic sediments. However, I would consider Tuff to be an igneous rock because of its mode of origin- It is mainly from consolidation of hot molten lava fragments.
Related Questions
drjack9650@gmail.com
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.