Questions:
Worksheet : Use the information gathered on the virtual field trip and the links to answer the following questions.
1. The pyroclastic rocks of Sunset Crater are basaltic; why did their eruption form a cone rather than a basalt flow like the Bonito Flow?
2. Why does the Bonito flow come out of the bottom of the cinder cone?
3. Why are the basalt flows so much denser than the cinders?
4. At one time scientists thought that basalt was deposited from water. What evidence is there that the lava flow was once molten? What evidence is there that the squeeze-ups were once semi-solid when extruded?
5. The two levels observed in the Bonito flow represent two stages of extrusion. How could you distinguish these two stages of eruption? Unlike the case for sedimentary rocks, in which older rocks always underlie younger rocks, the younger lava flow is below the older. Why?
6. How did the agglutinate mounds on top of the Bonito flow get to their present positions? Note that there is a dip in the crater rim above the point where the flow exits the cone. Why is it there?
7. How is a lava tube formed?
8. How did the xenoliths get to their present location? Even though they are enclosed by lava, they are not melted. Why might this be the case?