The rock cycle describes how rocks change form over long periods of time through various physical processes. There are three main types of rocks - igneous, sedimentary, and metamorphic - and each can change into another through the processes of cooling, weathering and erosion, compaction and cementation, heat and pressure (metamorphism), and melting. The rock cycle begins with molten rock that cools to form igneous rock. Erosion produces sediment that is buried and compacted into sedimentary rock. Further burial and heat causes metamorphism into metamorphic rock, which at high heat and pressure can melt back into magma to restart the cycle.

1. THE ROCK CYCLE

2. LESSON OBJECTIVES
• Name at least five (5) rock forming processes.
• Define accurately the rock forming processes.
• Label accurately the rock cycle.
• Explain with the aid of diagram the rock cycle
and the rock forming process.
• Create a model of a sedimentary rock and
then change the rock to igneous using
knowledge gained about rock formation.

3. What is the Rock Cycle?
• The rock cycle is the process by which rocks of one kind change
into rocks of another kind.
TYPES OF ROCKS:
• There are three main kinds of rocks:
– igneous rock,
– metamorphic rock, and
– sedimentary rock.
• Each of these rocks can change into the other kinds by physical
processes.
– Cooling
– Weathering and erosion,
– Compacting and cementing,
– heat and pressure (metamorphosis),
– Melting

4. The Rock Cycle Process
1. The rock cycle begins with molten rock. Molten rock is
called magma when it is below ground, and lava when it
is above ground. When magma cools and hardens, it
forms igneous rock. This process is called cooling or
solidification or crystallization.
2. Weathering and erosion, break the original rock into
smaller pieces. The smaller material is called sediment
and is carried away (transported) by rivers, wind, and
glaciers and deposited elsewhere. These sediments can
then be buried and hardened (called compaction and
cementation) forming sedimentary rock. This process is
called lithification.

5. 3. Sedimentary rock can be deeply buried and be
exposed to heat and pressure, which over time,
cause it to change its structure into
metamorphic rock. This process is called
Metamorphism, which means change.
4. Eventually, these metamorphic rocks may be
heated to the point where they again melt into
magma and the process or cycle starts again.

15. TYPES OF ROCKS
• Rocks are not unchangeable! Rocks
undergo changes of form in a rock cycle.
• A metamorphic rock can become an
igneous rock, or a sedimentary rock can
become a metamorphic one.
• Rocks change very slowly under normal
conditions.
• So what are the three types of rocks, and
how do they change into each other?

16. Three types of rock:
• Igneous rocks are formed when hot magma (melted
rock) is rapidly cooled. Granite, obsidian, and pumice
are all common examples of igneous rocks.
• Sedimentary rocks are formed by layers of sediment
(dirt, rock particles, etc.) being mixed and compressed
together for extended periods of time. Common
examples of these rocks are limestone, sandstone, and
shale. Sedimentary rocks often have lots of fossils in
them because plants and animals get buried in the
layers of sediment and turned into stone.
• Metamorphic rocks are a combination of rock types,
compressed together by high pressure and high heat.
They usually have a more hard, grainy texture than the
other two types. Schist, slate, and gneiss are
metamorphic rocks.

17. THE ROCK CYCLE
These rocks change over hundreds of years in the five steps of
the rock cycle:
(1) Weathering & Erosion:
Igneous, sedimentary, and metamorphic rocks on the
surface of the earth are constantly being broken down
by wind and water. Large rocks are worn down to small
particles. When the particles are broken off a rock and
stay in the same area, it is called weathering. When
the particles are carried somewhere else, it is called
erosion.
(2) Transportation & Deposition:
Eroded rock particles are carried away by wind or by
rain, streams, rivers, and oceans. As rivers get deeper
or flow into the ocean, their current slows down, and
the rock particles (mixed with soil) sink and become a
layer of sediment.

18. (3) Compaction & Cementation (Lithification):
As the layers of sediment stack up (above water or below),
the weight and pressure compacts the bottom layers.
Dissolved minerals fill in the small gaps between particles
and then solidify, acting as cement. After years of
compaction and cementation, the sediment turns into
sedimentary rock.
(4) Metamorphism:
Over very long periods of time, sedimentary or igneous
rocks end up buried deep underground, usually because of
the movement of tectonic plates. While underground, these
rocks are exposed to high heat and pressure, which changes
them into metamorphic rock. This tends to happen where
tectonic plates come together: the pressure of the plates
squish the rock that is heated from hot magma below.
(Tectonic plates are large sections of the earth’s crust that
move separately from each other. Their movement often
results in earthquakes.)

19. (5) Rock Melting:
Metamorphic rocks underground melt to
become magma. When a volcano
erupts, magma flows out of it. (When
magma is on the earth’s surface, it is
called lava.)
As the lava cools it hardens and becomes
igneous rock. As soon as new igneous rock is
formed, the processes of weathering and
erosion begin, starting the whole cycle over
again!

20. CLASSWORK
• Write the definition for the following rock
forming processes:
1) Cooling (solidification/crystallization)
2) Weathering
3) Compaction
4) Metamorphism
5) Melting