Introduction to Geology
June 22, 2008
This was a very interesting experiment, and the best of all was that it was simple. I eve did this experiment with my sister, with whom I went to the filed trip to Cuicocha as well, so she really did understood what happened in that volcanic scenario.
Now I will proceed to explain what happened in this experiment but first is important to notice that after I did the suggested experiment, I popped the balloon to see what to see the result; it was what I expected, a explosive volcanic eruption, which results can be seen in picture number 4. Now the explanation:
The flour at the top of the cone collapses because there is not enough force to hold it up. In volcanoes, a large ash eruption or removal of magma to a deeper level reduces the pressure and causes the rocks at the summit to collapse. A large collapse associated with an eruption forms a caldera. A smaller collapse associated with removal of magma to a deeper level forms a crater.
How this demonstration is like real calderas
1. Gas pressure holds the overlying material in place
2. Removal of gas pressure causes collapse
3. The collapse feature is circular
4. Size of the collapse feature is related to the amount pressure released.
How this demonstration is NOT like real calderas
1. Calderas form from large explosive ash eruptions
2. Water vapor, sulfur dioxide, and carbon dioxide, not air, are the common volcanic gases.