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Chapter 3
Rocks
Rock – a mixture of minerals, rock
fragments, volcanic glass, organic
matter, or natural materials.
(example: Granite is made up of feldspar,
quartz, mica, and hornblende)
Rock Cycle – a model that illustrates the
processes that create and change rock
Sediment
4
Sedimentary
Rocks
5
3
3
2
5
2
Igneous
Rocks
3
Metamorphic
Rocks
2
1
Magma
1 – Cooling 2 – Melting 3 – Weathering and Erosion
4 – Compaction and Cementation
5 – Heat and Pressure
The Principle of Conservation of Matter –
matter is never created or destroyed but is
redistributed in other forms
Igneous Rocks
Igneous Rock – form when hot magma
cools and hardens
1. Intrusive Rocks – rocks that form
when magma cools below the surface of
the Earth
-Cool slowly, so they have minerals that
are large.
2. Extrusive Rocks – rocks that form when
lava cools on the Earth’s surface
-lava – when magma reaches Earth’s
surface and flows from volcanoes
- cool quickly, so minerals are small
3. Volcanic Glass – rocks that cooled so
quickly that few or no minerals are
formed.
-pumice, obsidian, and scoria
Classifying Igneous Rocks
1. Basaltic – igneous rocks that are dense,
and dark colored
-high in iron and magnesium and low in
silica
2. Granitic – igneous rocks that are light
colored of a lower density
-contains a lot of silica and less iron and
magnesium
3. Andesitic – igneous rocks that are
between basaltic and granitic
Metamorphic Rocks
Metamorphic Rocks – rocks that have
changed because of changes in
temperature and pressure or the presence
of hot, watery
Classifying Metamorphic Rocks
1. Foliated texture – when mineral grains
line up in parallel layers
-ex. Slate & Gneiss
2. Nonfoliated texture – mineral grains grow
and rearrange, but don’t form layers
-ex. Quartzite & Marble
Sedimentary Rocks
Sedimentary Rock – forms when
sediments are pressed and cemented
together, or when minerals form from a
solution
-often form in layers
-usually older layers are on the bottom
Sediment – loose material such as rock
fragments, mineral grains, and bits of shell
that have been moved by wind, water, ice
and gravity
Classifying Sedimentary Rocks
1. Detrital Sedimentary Rocks
a) made from broken fragments or other
rocks
b) Sediments are compacted and cemented
together
-weathering – breaking of rocks into
smaller pieces
-compaction – pressure from upper
layers pushes sediments together
-cementation – occurs when minerals
like quartz, calcite, and hematite are
deposited between pieces of sediment
2. Chemical Sedimentary Rocks
a) form when dissolved minerals come
out of a solution
b) limestone & rock salt
3. Organic Sedimentary Rocks
a) rocks made of the remains of onceliving things are called organic
sedimentary rocks
b) mussels, clams, corals, & snails
eventually become calcite
-coquina
c) ex. Chalk and Coal