2. Chapter Menu Lesson 1: Relative Ages of Rocks
Lesson 2: Absolute Ages of Rocks
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3. 7.1 Relative Ages of Rocks uniformitarianism rock cycle clast
lithification
stratum
superposition
relative age

4. The Beginning of Modern Geology
7.1 Relative Ages of Rocks
The Beginning of Modern Geology
James Hutton was the first person to realize that one process formed rock and another process tore it down.

5. The Principle of Uniformitarianism
7.1 Relative Ages of Rocks
The Principle of Uniformitarianism
Scientists can observe the processes that are active today, and interpret what happened in the past.
Uniformitarianism states that the same Earth processes have been at work for a very long time.
Geological processes that are at work today were also at work in the past.
Geological processes are so slow that direct observation is not possible.

6. Textbook Connection
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7. 7.1 Relative Ages of Rocks
The Rock Cycle
The rock cycle is a series of processes that make and change rocks through:
heating
melting
cooling
uplift
weathering
burial
increasing pressure
Metamorphosis

8. The Rock Cycle (cont.) 7.1 Relative Ages of Rocks
How are Earth materials broken down?

9. 7.1 Relative Ages of Rocks
The Rock Cycle (cont.)

10. Three Major Types of Rocks
7.1 Relative Ages of Rocks
Three Major Types of Rocks
Igneous rocks
produced when magma solidifies
Metamorphic rocks
any rock that is put under extreme pressure or heat
Sedimentary rocks
form from compacted and cemented sediments

11. Igneous Rocks – A Closer Look

12. Metamorphic Rocks – Closer Look

13. Sedimentary Rocks – Closer Look

14. Sediment Formation and Layering
7.1 Relative Ages of Rocks
Sediment Formation and Layering
Sedimentary rocks form from preexisting rocks.
Four steps in the formation process:
Weathering
Transportation
Deposition
Lithification

15. 7.1 Relative Ages of Rocks
Weathering
Weathering is the physical or chemical breakdown of rocks into smaller pieces.
Physical weathering breaks down rocks without changing the mineral composition.

16. 7.1 Relative Ages of Rocks
Weathering
Weathering is the physical or chemical breakdown of rocks into smaller pieces.
Chemical weathering changes the mineral composition of rocks.

17. 7.1 Relative Ages of Rocks
Weathering (cont.)

18. MASS WASTING Transportation
7.1 Relative Ages of Rocks
Transportation occurs when sediments move downhill to lower areas and come to rest.
Clasts, different-sized sediments such as large boulders to microscopic bits of rocks that require different amounts of force to move them.
MASS WASTING

19. 7.1 Relative Ages of Rocks
Deposition
Deposition occurs when sediment being transported by water, wind, or a glacier slows down or stops.
This usually happens in low areas called depositional environments.
Two characteristics are parallel, horizontal layers, and sorting.

20. 7.1 Relative Ages of Rocks
Lithification
Lithification occurs when older sediment layers become compacted beneath younger layers.
Mineral-rich liquids seep into the pore spaces between the sediment grains.
The water evaporates and the minerals are left behind to cement the grains together.

21. Weathering in Review – Erosion Review
End of Chapter 7, Lesson 1, part 1

22. Textbook Connection
Take a few minutes – Read pages