Transcript The Rock Cycle

The Rock Cycle
What is the Rock Cycle?
The idea that rocks are
continually changing
from one type of rock
to another through
Earth’s natural
processes.
Are any of these rocks being
created or destroyed throughout
the processes of the rock cycle?
Key Words to Understanding the
Rock Cycle:
Igneous
Intrusive
Cooling
Heat
Sediment
Metamorphic
Extrusive
Melting
Pressure
Sedimentary
Magma
Lava
Crystallization (Crystal Size)
Weathering
Compacting
Erosion
Cementing
Deposition
Igneous Rock
Igneous rock is formed when
magma or lava cools and
crystallizes:
INtrusive – when magma cools
INside;
cools slower = larger crystals
EXtrusive – when lava cools
OUTside;
cools faster = smaller crystals
What is the
difference between
lava and magma?
Metamorphic Rock
Metamorphic rock forms
from heat & pressure
Metamorphic means “to
change form” –
represents a chemical
change
Usually forms deep in
Earth’s crust BUT it can
form anywhere there is a
lot of heat & pressure
Where could these
regions of heat or
pressure occur?
Sedimentary Rock
Sedimentary rock is formed by
layers of sediment being
pressed together over time.
Erosion and weathering near
Earth’s surface
Sediments are transported from
one place to another &
deposited in layers with the
oldest sediment on the bottom
The layers become compacted
and cemented together
What could these
sediments be
composed of?
Extra Vocabulary Help
Please read through the next slides if you
need clarification on any of the vocabulary
presented in this lesson!
Slides 16-18: Igneous Vocab
Slide 19: Metamorphic Vocab
Slides: 20-27 Sedimentary Vocab
Melting & Cooling
Melting is the result of continued heating
Leads to production of magma or lava and new igneous rocks
which are formed when the the magma or lava cools.
Cooling leads to the magma or lava forming a solid igneous rock.
Magma is molten rock that is still inside of Earth
Lava is molten rock that is on Earth’s surface
Crystallization
When the magma or lava gets cool enough the minerals that will
make up the rock begin to crystallize and form an intergrown
mass of crystals.
If the crystals begin to form deep in the Earth where it is
relatively warm the magma cools slowly allowing the crystals to
grow relatively large.
If the magma reaches the surface, the lava cools quickly and the
crystals do not have time to grow very large.
If the crystals cannot grow at all and volcanic glass is formed.
This is what causes intrusive or extrusive igneous rocks
Heat and Pressure
Metamorphic rocks trapped underground are still subject to
enormous heat from rising magma, or heated water, and pressure.
Sometimes the heat can get so intense the rocks actually melt, but
often the change occurs when the rock is still a solid!
Pressure comes from the incredible weight of material surrounding
the rock on all sides. Or, for example millions of years of
sediment on top of each other.
The pressure pushes new minerals into the rock and drives other
minerals out; the result, of course, is that the rock is chemically
changed.
Sediment
Examples of sediment can be pretty much anything like…
Materials, originally suspended in a liquid, (usually water) that
settles at the bottom of the liquid when it is left standing for a
long time – stream beds, mouth of rivers etc
Material eroded from preexisting rocks that is transported by
water, wind, or ice and deposited elsewhere
Organic material such as fossil fragments, shells, seeds, bones
etc.
Weathering
The process in which rocks are broken down by chemical and/or
physical processes into smaller particles.
There are three types of weathering
Physical Weathering: physical action which breaks up rocks.
An example of this is freezing & thawing of water trapped in
the cracks or pores of rocks.
Chemical Weathering: When the rock is attacked by
chemicals. An example of this is how acid rain breaks down
limestone.
Biological Weathering: Occurs when rocks are weakened and
broken down by animals and plants. A tree root system that is
slowly splitting rocks is an example of this type of
weathering.
Erosion
Erosion is the wearing away, or “mass wasting” of exposed
surfaces by natural forces such as wind, moving water and
ice. Rock fall under gravity is also erosion.
This is the removal process that follows weathering.
Compaction
The result of this pressure
is a compaction of the
sediment
The sediment is squeezed
or “compacted” together
causing a reduction in
pore space and a sticking
together of the grains.
The pressure is often a
result of the layers of
sediment on top pressing
down on older layers.
Cementation – taking
Compaction a step further
Most sediments are
deposited in water
containing dissolved
minerals.
The water flows through
the sediment and some of
these minerals precipitate
on the grain surfaces.
With time, the liquid
material effectively glues
the sediment together into
a cohesive solid - a
sedimentary rock.
Deposition & Transportation
The transportation process occurs when the
particles created by weathering are carried
or moved by ice, air, or water to a different
location.
The sediment is then deposited or laid to
rest in that new location.