Geology Reference
In-Depth Information
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These two types of basalt lava were first observed and named in Hawaii, but now scientists use the
terms pahoehoe and a'a to describe basalt lava flows with these characteristics no matter where they
are located.
When magma becomes lava: Studying volcanoes
Extrusive igneous rocks are also called
volcanic
rocks. That's because they are created
from lava that erupts from volcanoes.
Volcanoes
are the geologic structures that result
from magma forcing its way up through the crustal layer of the earth and reaching the
surface. When the magma reaches the surface, it erupts as lava.
In this section, I give you an overview of volcanoes so you can understand how extrus-
ive igneous rocks are created.
Spotting volcanic features
