Igneous Rocks
The first rocks to form on earth probably looked
much like the igneous rocks that harden from lava
today. Igneous rock is any rock that forms from
magma or lava. The name “igneous” comes from
the Latin word ignis, meaning “fire”.
Meet IGGY
“Iggy” is an igneous rock. He is here to let us know that he can form in
one of two ways. Not only can he form from large impressive volcanic
explosions but also more slowly, less dramatic ways under the earth.
Most igneous rocks are made of mineral crystals.
They are formed Extrusively or Intrusively.
~ Extrusive Rock is igneous rock formed from lava that
erupted onto the Earth’s surface.
~ Basalt is the most common extrusive rock. Basalt
forms much of the oceanic crust, shield volcanoes,
and lave plateaus.
Meet “Bubbles” Basalt, a relative of Iggy. She is fine grained and
contains some large crystals. Bubbles has a bubbly surface.
She is dark gray with black, dark brown and reddish brown
tones. She is found any where volcanoes are or have been
active. Mostly consists on the oceanic and continental crusts.
Intrusive Rock is igneous rock that formed when
magma hardened beneath Earth’s surface. Granite
is the most abundant intrusive rock in continental
crust. This occurs when magma flows away from
the volcanic activity to another place underground
where it cools slowly inside the earth.
Meet “Giant” Granite, another
relative of Iggy. He has large
particles that are easily seen
and is a speckled light and
dark color. Giant is typically
white to gray, pink or red.
Found largely in the
continental crust especially
throughout the mountains of
North America.
Igneous rocks are hard, dense and durable. People throughout history
have used igneous rock for tools and building materials
Example:
Native Americans used obsidian for making very sharp tools
Granite has a long history as a building material.
Sedimentary Rocks
Meet SED:
Sed is a sedimentary rock. He is here to let us know that he is
formed from small particles of rock and other debris that get
squashed together. He is really cool with any sediments that
come his way. He will accept any particle no matter how far it
may have traveled.
Lay it
On me, man……
~ Sedimentary rocks form from particles deposited by water
and wind.
~ Along the beach, a stream you will see tiny sand grains, mud
and pebbles. These are what make up sedimentary rocks.
~ Water, wind and ice will carry the sediments, depositing
them in layers.
Erosion:
~ Destructive forces such as heat and cold, rain, waves and
grinding ice are constantly breaking up and wearing away
all the rocks on surface.
~ rushing water or wind loosen will carry away the fragments
of rock.
Water
Deposition: is the settling out of the sediments after it has been carried away
by wind or water.
~ If in water, the water will slow and allow the sediments to drop to the
bottom of a river or lake.
~ Sediments may include: shells, bones, leaves, stems and other remains of
living things.
~ These living things will eventually settle, slowly harden and change into
fossils.
Compaction:
~ At first the sediments fit together loosely. But gradually, over
millions of year, thick layers of sediment build up. These are
layers are heavy and press down on the layers beneath them.
~ This is compaction.
~ These layers are easy to see in rock.
Meet “Sandy” Sandstone:
Cousin to Sed, she is fine to medium particle shaped and it a gray to red
to brown color. She loves the ocean as she typically forms from the
sand on the beach, ocean floor, river beds or even in sand dunes. She
comes together nicely through the after getting compacted then
cemented together with other fine particles like her self.
Meet “Smooth-Talkin’” Shale:
Another cousin to Sed, “smooth talkin’” is made of fine grains and
particles that are not visible, and yes he even contains fossils. He is a
smooth gray, or brown or sometimes a reddish brown. Shale is so
smooth because he is made of clay. He forms when water deposits
clay in very thin, flay layers one on top of each other. While is
smooth he can be spit easily
Meet “Bones” Limestone:
Cousin to Sed, “Bones” is fine grained with a pitted, crumbly-looking surface that may
contain fossils. He is light gray to dark gray and on the rare occasion a yellow or
brown. He is an ocean lover because many living things like coral, oyster, snails,
shells or skeletons pile up as sediments on the ocean floor. Over Millions of years
these layers grow as deep as hundreds of meters. Weight of the layers builds up and
squashed “Bones” together.
So our rock started off being blasted out of a volcano and ended up as a
grain of sand that turned into a sedimentary rock. It could simply stay
as a sedimentary rock or it could get hotter and hotter and be under
more and more pressure so that he has to “morph”.
Metamorphic Rocks
~ Heat and pressure deep beneath Earth’s surface can change any rock
into metamorphic rock.
~ Collisions between earth’s plates can push the rock down toward the
heat of the mantle.
~ Pockets of magma pushing up through the crust also provide heat.
~ The deeper the rock is buried the more pressure it placed on the rock.
The minerals in the rock can change into other minerals.
Some Metamorphic rock will foliate: meaning
they become thin and flat, leaf like.
Meet “Morph”:
Whoa, I’m hot! I can’t take all this pressure!
How much more time do I have to spend
here?