Day 4
What are the three major types of rock?
igneous, metamorphic & sedimentary
Based on the rock samples from the
Compare Rock Types activity, what do
most rocks appear to have in common?
Most rocks are made of minerals.
Daily Warm-Up Exercises
1
Compare Rock Formation, Part 1
Contrasting Case Activity 2
Earth History, Investigation 8
Compare Rock Formation
2
Do you remember…
...how igneous rocks form?
An igneous rock forms
when molten rock cools
and hardens.
granite
Igneous comes from the Latin word
ignis, which means fire.
pumice
Compare Rock Formation
3
Do you remember…
...how metamorphic rocks form?
A metamorphic rock forms when
an existing rock changes due to
heat and/or pressure.
Metamorphic means change in form.
Compare Rock Formation
schist
quartzite
4
Cross Section of Earth
Inner Core:
solid
4700°C to 4800°C
3 to 4 million times SP
Outer Core:
liquid
3450°C to
1 to 3 million times SP
4700°C
Mantle:
upper (outer) part = rigid solid
lower part = soft (plastic) solid
1200°C to
3450°C
32,000
to 1 million times SP
Crust:
rigid solid
temperature can reach 1200°C
pressure is up to 32,000 times surface pressure (SP)
Which is Which?
Igneous Rock 1 –
11 – granite
This rock is formed when molten rock cools and hardens.
This process happens when magma pushes up into the
crust but remains trapped underground. The temperature
there is very warm, so the magma cools and hardens
slowly. This slow cooling results in the formation of large
crystals that are easily visible without a hand lens.
This rock makes up a large portion of Earth’s crust and
mountain ranges. Because it forms deep underground, it is
not visible until the earth above it erodes or is dug up. This
rock is rough and dull, but it has crystals that look smooth
and shiny. It is also very hard and long-lasting, so it is often
used for headstones and other monuments.
Igneous Rock 2 –
Look at rocks 11 & 16.
Can you figure out
which rock goes with
which description?
16 – obsidian
This rock is formed when molten rock cools and hardens.
This process happens when a volcano erupts and molten
rock cools quickly on Earth's surface. In fact, it cools so
quickly that no crystals form at all. Instead, it forms a glass.
This rock is smooth, shiny, and hard. Because it doesn’t
have a crystal structure, it splits along smooth, curved
edges. This feature makes it ideal for creating razor sharp
tools. Such tools are often found during archeological digs,
and some modern surgeons prefer blades made of this rock
because they are sharper and thinner than steel.
Do you remember
what rock 11 is
called?
6
Compare Igneous Cases
Question
Fill in the table by
entering information
from the paragraphs
to answer each
question.
Different
Granite –
case 1 = granite (11)
case 2 = obsidian (16)
Same
How does the
rock form?
Use this
column for
information
that is true
about both
rocks.
Use this
column for
information
that is true
Obsidian
about– one but
not the other.
Granite –
What features
result from
this process?
Compare Rock Formation
Obsidian –
7
Igneous Rock Formation
Question
Same
Different
Granite –
How does the rock
form?
Molten rock cools
and hardens.
hardens slowly
because the molten rock is
trapped underground, where it
is very warm
Obsidian – hardens quickly when
a volcano erupts and molten
rock cools on Earth's surface
Granite –
What features
result from this
process?
rough & dull, with
large crystals that look smooth
& shiny; very strong
The rock is hard.
Obsidian –
no crystals; glass;
smooth & shiny; splits along
smooth, curved surfaces
Compare Rock Formation
8
Which is Which?
Metamorphic Rock 1 –
20 – slate
This rock forms when shale, a sedimentary rock, changes due to
heat and pressure. This process happens deep beneath Earth’s
surface.
Before the change, shale is a smooth, hard, dull rock with very
fine grains arranged in layers. After the change, the new rock is
also smooth with very fine grains, but it is harder, shinier, and
more compact than shale. Shale often contains fossils, but the
new rock rarely does. The biggest change is that the new rock
can be easily split into sheets of different thicknesses. For this
reason, it is often used to make roofing tiles and paving stones.
Metamorphic Rock 2 –
Look at rocks 1 & 20.
Can you figure out
which rock is which?
1 – schist
This rock forms when slate, a metamorphic rock, changes due to
extreme heat. This process happens deep beneath Earth’s
surface.
Before the change, slate is smooth, fairly shiny, and hard. After
the change, the new rock is rough and shiny, and small pieces
tend to flake off easily. The biggest change is in grain size. Slate
has very fine grains. The new rock has medium to coarse
crystals that are flat and arranged in layers. Fossils are rarely
found in slate or in the new rock.
Do you remember what
rock 1 is called?
9
Compare Metamorphic Cases
Question
case 1 = slate (20)
case 2 = schist (1)
Fill in the table by
entering information
from the paragraphs
to answer each
question.
How does
the rock
form?
Same
Use this
column for
information
that is true
about both
rocks.
Different
Slate –
Use this
column for
information
that is true
about
Schist
– one but
not the other.
Slate –
What
features
result from
this
process?
Compare Rock Formation
Schist –
10
Metamorphic Rock Formation
Question
Same
Different
Slate – changes are caused by heat
and pressure
How does the
rock form?
An existing rock
changes due to
heat and/or
pressure.
Schist – changes are caused by
extreme heat
Slate –
What features
result from
this process?
Fossils are
usually
destroyed.
new rock is harder, shinier,
and more compact; easily splits
into sheets of different
thicknesses
Schist –
very fine grains become
medium to coarse crystals that
are flat and arranged in layers
Compare Rock Formation
11
Compare Igneous & Metamorphic
Look at your igneous table. Based on these two
rocks, how do igneous rocks form?
Igneous rocks form when molten rock cools
and hardens. This process can happen
slowly or quickly.
Look at your metamorphic table. Based on these
two rocks, how do metamorphic rocks form?
Metamorphic rocks form when an existing
rock changes due to heat and/or pressure.
Compare Rock Formation
12
Compare Igneous & Metamorphic
What properties result from igneous formation?
Igneous rocks are usually hard. They
usually have crystals, but obsidian
does not have crystals.
What properties result from metamorphic
formation?
Metamorphic rocks rarely have fossils
because they are usually destroyed by the
heat and/or pressure.
Compare Rock Formation
13