Geology

Geology
Project description
GEOG 1021: Lab Assignment #3: Igneous Rocks
1. How does magma differ from lava? 2
2. How does the manner in which magma is generated at a convergent boundary differ from that at divergent boundary? (3) How is this reflected in the composition of igneous rocks that tend to form in these settings? (2) 5
3. Could phenocrysts be found in obsidian? (Yes or No (2). Explain your answer briefly. (3) 5
4. What are the fundamental differences between granite and diorite? In what sense do they share similar characteristics? 4
5. Why are felsic lava flows so much more viscous than mafic ones? 3
6. Most rock inside Earth is hot enough to be molten under Earth surface conditions, but it is not molten inside the planet. Why not? 4
7. Two aphanitic igneous rocks have the following compositions: 4
• Specimen A: 15% biotite; 15% sodium plagioclase; 60% potassium feldspar, and 10% pure quartz
• Specimen B: 10% olivine; 55% pyroxene; and 10% plagioclase.
Which of the two aphanitic rock samples has mafic composition? Which one has felsic composition? Use Figure 1 at page 2 to get your answer.