Rocks: Unearthed!
In this small section you will learn about the types of rocks minerals form. There are
three types of rocks created by minerals. The three classes are igneous,
sedimentary, and metamorphic. And this is where it
starts….
Igneous Rock:
The cooling of lava after a volcano eruption creates igneous rocks. The heated minerals
(lava) rise up to the surface and ooze from the volcano and form rocks like:
Pumice, and Granite. An important thing to remember about these rocks is that
they are cooled quickly and that it makes them more
porous.
Sedimentary Rock:
The layering of rocks/minerals/water from
above forms sedimentary rocks. This happens in two ways: cementation and
compaction. Cementation is where a substance glues rocks/minerals together along
with erosion and weathering to create rocks like conglomerate. Compaction is the
pressure of water and materials to crush minerals/rocks together to create a
different rock like sandstone. Minerals that mainly show up in sedimentary rocks
are: sand, gravel, mud/clay, and dissolved chemicals or sediments. These are the
only rocks that contain fossils.
Metamorphic Rock:
Metamorphic rocks are basically igneous or sedimentary rocks change by heat and pressure
from deep within the earth. Metamorphic rocks are more compact but much less
porous from its original state. For example: Shale (sedimentary) will get pushed
down farther and farther into the earth until the heat and pressure will force
it to change into slate (which used to be used in the making of blackboards).