2. Earth as a system
The Earth system is powered by energy from the sun that drives the external processes in the
Atmosphere
Hydrosphere
Biosphere
Geosphere (lithosphere)
Earth system is also powered by internal processes driven by heat flow within earth. What are some sources of heat?

3. Figure 1.4
Was this rock formation the result of internal or external processes?
What had to occur for this arch to form?

4. Can you think of one or more internal processes that are of interest to geologists?
Can these processes be explained?

6. Two views of Pakistan Charakusa Valley, Karakorum Range

7. Muzzaffarabad

8. Natural Hazards
One important reason to study geology and be able to predict processes is to prevent threats to humans
A natural hazard is just that – natural process. It only becomes a hazard when humans put themselves in harm’s way.

9. The Science of Geology
Geology - the science that pursues an understanding of planet Earth
GEO=earth OLOGY = study of
Physical geology - examines the materials composing Earth and seeks to understand the many processes that operate beneath and upon its surface
Historical geology - seeks an understanding of the origin of Earth and its development through time

10. The Science of Geology Some historical notes about geology
The nature of Earth has been a focus of study for centuries
Catastrophism
Uniformitarianism and the birth of modern geology
James Hutton: Theory of the Earth Late 1700s – birth of modern Geology

11. The nature of scientific inquiry
Science assumes the natural world is consistent and predictable
Goal of science is to discover patterns in nature and use the knowledge to make predictions
Scientists collect data through observation and measurements

12. The nature of scientific inquiry
How or why things happen is explained using a
Hypothesis – a tentative (or untested) explanation
Theory – a well-tested and widely accepted view that the scientific community agrees best explains certain observable facts

13. Box 1. 2 Do glaciers move. (pg
Box 1.2 Do glaciers move? (pg. 11) Rhone Glacier, Switzerland, credit: L. Agassiz

14. The nature of scientific inquiry
Scientific method involves
Gathering facts through observations
Formulation of hypotheses and theories
There is no fixed path that scientists follow that leads to scientific knowledge

15. Solar Nebular Hypothesis
Is this hypothesis created
by direct or indirect observation?
How do you think this model was made?

16. Early evolution of Earth
Origin of planet Earth
Nebular hypothesis
Assumes a flat, disk shape with the protosun (pre-Sun) at the center
Inner planets begin to form from metallic and rocky substances
Larger outer planets began forming from fragments of ices (H2O, CO2, and others)

17. Early evolution of Earth
Origin of planet Earth
Most researchers believe that Earth and the other planets formed at essentially the same time
Nebular hypothesis
Rotating cloud called the solar nebula
Composed of hydrogen and helium
Nebula began to contract about 5 billion years ago

18. Figure 1.9A
How did the moon form? Do scientists agree?

19. Speaking of models…how did this diagram become a model of earth?

20. Early evolution of Earth
Formation of Earth’s layered structure
Metals sank to the center
Molten rock rose to produce a primitive crust
Chemical segregation established the three basic divisions of Earth’s interior
Primitive atmosphere evolved from gases in Earth’s interior

21. Earth’s internal structure
Layers defined by composition
Crust
Mantle
Core
Layers defined by physical properties
Lithosphere
Asthenosphere
Mesosphere
Inner and Outer Core

22. Earth’s Layered structure
Figure 1.16

23. Figure 2.29

24. Figure 1.5

25. Concept of Geologic Time
The second frame of reference for geologic time is absolute dating
Absolute dating results in specific dates for rock units or events
expressed in years before the present
Radiometric dating is the most common method of obtaining absolute ages
Such dates are calculated from the natural rates of decay of various natural radioactive elements present in trace amounts in some rocks