Download Science Notes 02-06-12 Section 1: Rocks Rock – is a mixture of

Science Notes 02-06-12
I. Section 1: Rocks
A. Rock – is a mixture of minerals, volcanic glass,
organic matter, and/or other
materials.
B. There are 3 basic types of rock, including igneous,
sedimentary, metamorphic
rock.
1. Igneous rock
a. The word igneous comes from the Latin word
igneus, which means fire.
An erupting volcano releases lava
b. Igneous rock is formed when magma or lava,
from a volcano, cool down and becomes a
solid.
Image 1 of 2: As lava cools it begins to solidify into igneous rock
Image 2 of 2
c. Magma trapped below the Earth’s surface can
cool and become intrusive igneous rock.
d. Magma cooling near the Earth’s surface or on
the surface (as lava) can cool and become
extrusive igneous rock.
extrusive vs. intrusive igneous rock*
e. Crystal size, large or small, can help identify
an igneous rock as intrusive or extrusive.
f. Some igneous rocks have holes that form from
the release of trapped hot gases as the rock is
forming from magma or lava.
g. The 3 types of igneous rock include:
i. Basaltic igneous rock- is dark-colored
and dense.
1. Contain iron and magnesium but very
little silica
2. Basaltic lava flows freely from a
volcano
ii. Granitic igneous rock- is lower in density
and of lighter color.
1. Contain more silica and less iron and
magnesium
2. Granitic lava is thick and stiff
iii. Andesitic igneous rock- has a more
balanced composition of minerals and
density compared to basaltic and granitic
igneous rock.
2. Sedimentary rock
a. Sedimentary rock is rock that forms from
sediments.
b. Sediments are the small fragments of rock,
mineral grains, and bits of plant/ animal
remains that eventually settle to the bottom.
i. Sediments are moved or taken to the
bottom of the ocean or canyons by wind,
water (rain), or gravity.
ii. Once there, pressure pushes these
sediments together to form sedimentary
rock.
c. Sedimentary rocks are classified by what they
are made of and how they formed.
1. Detrital sedimentary rocks- are
made from broken fragments of other
rocks.
a. When sediments stick together
because of pressure, compaction
occurs.
2. Chemical sedimentary rocks- are
made from rocks that are formed
mostly by minerals that grew out of a
solution.
3. Organic sedimentary rocks- are
formed from the remains of once
living plants or animals.
a. For example: Chalk is a type of
organic sedimentary rock
because it is made from the
microscopic calcite-shell remains
of animals.
These sea shells come from sea animals
After many years, sea shells get broken down into microscopic pieces.
These very small pieces become pressured together to become organic sedimentary
rock.
This piece of chalk is made from the microscopic calcite-shell remains
of sea animals. Chalk, therefore, comes from organic sedimentary rock.
More examples of sedimentary rock
Image 3 of 4: sedimentary rock (sandstone)
Image 4 of 4: Sedimentary rock (notice the different layers of rock)
Q: What type of rock is this and how do you know?
3. Metamorphic rock - is rock that forms from heat
and pressure.
a. The semiotics (meaning) of the word
metamorphic:
i. Meta means change, and morph means
shape.
b. Classification of metamorphic rock by
composition and texture:
i. Foliated texture- mineral grains flatten
and line up in parallel layers.
Metamorphic rock (Foliated Gneiss)
ii. Nonfoliated texture- mineral grains grow
and rearrange but do not form layers.
Nonfoliated Metamorphic rock (Nonfoliated Marble)
Nonfoliated Metamorphic rock (Hornfels)
II. Section 2: The Rock Cycle:
A. The Rock Cycle – is a model that shows the
processes that change rock
from one form to another.
B. Law of Conservation of Matter- is a law that states
that matter cannot be created or destroyed.
i. Rocks are matter; therefore, the rock cycle never
destroys the elements of rock but instead
redistributes them.
ii. James Hutton, MD., recognized the rock cycle in
1788 by observing Siccar Point, Scotland.
1. He is considered the father of modern
geology.
Geologist James Hutton posing for a painting
A picture of Siccar
Point in Scotland –
notice the layers of
different rock
Pic 2: Siccar point
in Scotland
*End Notes*