1. Rocks and the Rock Cycle
Three Rock Types
Igneous Rocks
Sedimentary Rocks
Metamorphic Rocks
All rock types are interrelated through the rock cycle.
Reference: Tarbuck and Lutgens Pages

2. Igneous Rocks
An igneous rock is formed when magma or
lava cools and solidifies

3. Igneous Rocks Formed by the cooling and hardening of hot molten rock.
If the molten rock is located within Earth it is called magma.
If the molten rock reaches the surface and exits through volcanoes, it is then referred to as lava.
Two classifications of Igneous rock;
1) Plutonic (intrusive) – forms from magma.
2) Volcanic (extrusive) – forms from lava.

4. Molten rock Igneous Rocks in the Earth is magma
Magma is buoyant, rises to surface,
& sometimes breaks through
when magma reaches Earth’s surface it
is called lava

5. Igneous Rocks Why should we care?
Igneous rocks make up bulk of Earth’s crust
Earth’s mantle is basically one huge igneous rock
Important rocks economically
Striking landscape features

6. Igneous Rocks
Igneous rocks that form
- at the surface are volcanic (extrusive)
Igneous rocks that form
- deep down are plutonic (intrusive)

7. Plutonic rocks To see them, they must be uplifted to surface
Igneous Rocks
Plutonic rocks
To see them, they must be uplifted to surface
And softer surrounding rock eroded away
Magma body

8. Igneous Rocks Plutonic rocks
For us to ever see them, they must be uplifted to the surface
And softer surrounding rock eroded away

9. Plutonic igneous rock example: El Capitan Igneous Rocks
Yosemite Nat. Park,
California

10. As magma cools, atoms arrange in an orderly crystal structure
Igneous Rocks
As magma cools, atoms arrange in an
orderly crystal structure
crystallization

11. Igneous Rocks
Note: different crystal sizes

12. Igneous Rocks Coarse-grained igneous rock Close up of crystals
Note the variety of crystal sizes

13. Sedimentary Rocks
Rock formed when the weathered products of pre-existing rocks have been transported, deposited, and compacted or cemented into solid rock.
Usually formed in marine (water) environments where sediment is deposited by streams and rivers.
Most of Earth’s crust (95%) is igneous rock but the surface is covered by sedimentary rocks.
Three classifications of Sedimentary Rocks; ) Clastic (Detrital) - Fragments ) Chemical - precipitation and evaporation ) Organic – once living material
4) Biochemical

14. Metamorphic Rocks
Rock formed below Earth’s surface when pre-existing rock is altered by heat, pressure, and chemically active fluids.
Metamorphism changes rocks in size, shape, texture, and the minerals they contain.
Metamorphism varies in degree from;
High Grade. Ex. Granite changes to Gneiss.
Low Grade. Ex. Shale changes to Slate.

15. Rock Cycle Magma Metamorphic Igneous (Volcanic) (Plutonic)
Melting
Magma
Cool & Crystallize
Metamorphic
Igneous (Volcanic) (Plutonic)
Heat & Pressure
Weathering & Erosion
Sedimentary (Clastic) (Chemical) (Organic)
Compaction & Cementing
Sediment Sand, Silt, & Clay

16. Rock Cycle Magma Metamorphic Igneous (Volcanic) (Plutonic)
Melting
Magma
Cool & Crystallize
Melting
Metamorphic
Igneous (Volcanic) (Plutonic)
Heat & Pressure
Weathering & Erosion
Heat & Pressure
Weathering & Erosion
Sedimentary (Clastic) (Chemical) (Organic)
Weathering & Erosion
Compaction & Cementing
Sediment Sand, Silt, & Clay

17. Sample Problem
In the diagram below, rock types/materials are indicated by numbers and processes are indicated by letters. Indicate the rock types/materials and processes for the rock cycle diagram by completing the table below.
Answer: A
1. Magma E 2. 5. B D
Weathering & Erosion C 3. 4.
Rock Type / Materials
Process 1.
Magma A
Cool & Crystallize 2.
Igneous B
Weathering and Erosion 3.
Sediments C
Compacting & Cementing 4.
Sedimentary D
Heat & Pressure 5.
Metamorphic E
Melting