As the magma cools into a solid rock around the base of the volcano, it can be collected as samples of rocks such as basalt, pumice, or obsidian.
(the magma; cools; ) (it; can be collected; as samples of rocks such as basalt, pumice, or obsidian)
the magma it
cools can be collected
as samples of rocks such as basalt, pumice, or obsidian