In what states are they ejected?
What are the principal varieties of lava, and how are they distinguished?
Why is the basaltic lava the last to be ejected?
How is the age of the volcanic rocks determined?
What are the three divisions of the volcanic rocks, as dependent upon age?
What is the proportion of the volcanic to other rocks?
How many active volcanoes exist?
Describe the eruptions of Kilauea.
Describe the eruption in Iceland in 1783.
What are the dimensions of Mount Ætna, and how has it been produced?