The document discusses the three main types of rocks - igneous, sedimentary, and metamorphic - and the rock cycle by which rocks are formed and changed over time. It explains that igneous rocks form from cooling magma, sedimentary rocks form through compaction or cementation of sediments, and metamorphic rocks form from extreme heat and pressure changing existing rock types. The rock cycle involves the continuous transformation of rocks between these types through geological forces and processes.

1. Rocks and the
Rock Cycle
Mr. Silva

2. Three Major Types of
Rocks
• Igneous Rocks: “meaning from fire”
– Formed when magma cools and hardens.
– Magma is called lava when it reaches the
earth’s surface.

3. Three Major Types of
Rocks
• Sedimentary Rock:
– All types of rock, minerals, and organic matter
that have been broken into fragments by
forces.
• Wind, water, ice
– Deposits harden after being compressed
together.

4. Three Major Types of
Rocks
• Metamorphic Rock: “changed form”
– When an existing rock undergoes extreme
forces it changes form.
• Tremendous pressure
• Extreme heat
• Chemical processes

5. The Rock Cycle
• A cycle is a series of changes
– Geological forces and processes cause rock
to change from one type to another and back
again.
– Rocks in the crust have passes through the
cycle many times.

6. The Rock Cycle

7. Formation of Igneous Rock

8. Formation of Igneous Rock
• When lava cools and hardens it forms
igneous rock.
• The rock has two categories and is based
on how the lava cools.
– Intrusive igneous rock
– Extrusive igneous rock

9. Intrusive Igneous
• The cooling of magma deep below
the earth’s surface.
• Called intrusive because the lava
that forms them intrudes other
rocks.
• The magma then slowly cools to
form rock.
• The slow cooling allows minerals to
collect and form large crystals.

10. Extrusive Igneous
• Formed when there is a rapid
cooling of lava or melting of rocks
on the earth’s surface.
• The rapid cooling does not give
crystals time to form.
• The main difference between the
two types of igneous rock is the
size of the crystal when the rock is
forming.

11. Texture of the Rocks
• The larger the crystals, the more rough
the rock will be.
• When rapid cooling occurs and crystal are
not allowed the opportunity to form, the
rock will appear extremely smooth.
• Crystal formation will be so small that they
are not seen by the unaided eye.

12. Texture of the Rocks
• An igneous rock with both large and small
crystals is called porphyritic.
• The porphyritic texture is created when
lava cools slowly and is then sped up.

13. Texture of Rock
• When thick lava cools rapidly no crystals
form at all.
• Usually thicker lava has an increased
amount of trapped gases and this will
cause the igneous rock to become full of
holes.

14. Composition of Rock
• The mineral make of the lava determines
the chemical make-up of the rock.
• There are 3 different types of families:
– Felsic
– Mafic
– Intermediate

15. Formation of Sedimentary
Rock

16. Formation of Sedimentary Rock
• Made up of an accumulation of various
types of sediment.
• Compaction or cementation are two
process that form sedimentary rock.
– Compaction- when all air and water is
squeezed out of sediment
– Cementation- when minerals are left
between the fragments of sediment.

17. 3 Types of Sedimentary Rocks
• Clastic Sedimentary Rock- rock is made
up of rock fragments that have been moved
by water, wind or ice.
• Chemical Sedimentary Rock- forms
from minerals that precipitate from water.
• Organic Sedimentary Rock- forms from
the remains of organisms.

18. Clastic Sedimentary rocks
• Rocks are classified by the sediments size.
• Conglmerates- rocks composed of rounded
gravel size fragments or pebbles.
– Individual pieces are easily seen.
• The sandstone group is made up of sand size
grains that have been cemented together.
• The third group is shale, which consists of clay
size particles the easily flake or break apart.

19. Conglomerates

20. Sandstone

21. Shale

22. Chemical Sedimentary Rocks
• Rocks that form from
minerals that were once
dissolved by water.
• These rocks are called
evaporates.

23. Organic Sedimentary Rock
• Formed out of the remains of living things.
• Coal is a prime example of this.

24. Sedimentary Rock Features
• Easily identifiable
– Layering
– Ripples marks
– Mud
– Cracks
– Fossils
– Concretion

25. Formation of Sedimentary
Rock

26. Formation of Metamorphic Rock
• Changed from one type of rock into
another by heat, pressure, and chemical
processes.
• Form deep beneath the earth’s surface.
• ALL metamorphic rocks are formed from
existing igneous, sediment or
metamorphic rocks.

27. Formation
• Minerals may change in size or shape or
separate into parallel bands.
• Metamorphic formation happens two
different ways
– Contact metamorphism
– Regional metamorphism

28. Contact Metamorphism
• Formed when magma pushes through
existing rock.
• Changes the structure and mineral
composition of surrounding rock.

29. Regional Metamorphism
• Metamorphism sometimes occurs with
tectonic plate movement.
• Tremendous heat and pressure is
created at plates edge.
• This heat and pressure will cause
chemical changes in the rocks.
• Most metamorphic rock
is created be regional
metamorphism.

30. Classification of Rocks
• Rocks can be classified into two different
types based on their texture:
– Foliated
– Nonfoliated