Geologists gain understanding of the formation of magma and ...

[j.rubin]

Geologists gain understanding of the formation of magma and igneous rocks by making field observations, geochemical analyses, and laboratory experiments. Give an example of each.
 
  What will be an ideal response?

Question 2

Which of the nine igneous rocks shown in Figure 4.3 were formed during last century's eruptions of Mount St. Helens and Mount Pinatubo?
 
  What will be an ideal response?

[tanna.moeller]

Answer to Question 1

This is an open-ended question where students may refer to field studies of modern or ancient volcanoes, volcanic rock, and ancient intrusive rock exposed to the surface by erosion; geochemical studies including the identification and measurement of the abundances of elements in igneous rocks; laboratory experiments including melting and/or crystallization studies that mimic the temperature and pressure conditions inside Earth.

Answer to Question 2

Dacite