1. An Introduction to Physical Geology Chapter 1

2. Geology The science that pursues an understanding of planet Earth Physical geology – examines Earth materials and seeks to understand the many processes that operate on our planet Historical geology - seeks an understanding of the origin of Earth and its development through time

3. Geology, People, and the Environment Many important relationships exist between people and the natural environment Problems and issues addressed by geology include Natural hazards, resources, world population growth, and environmental issues

4. Brief History of Geology The nature of the Earth has been a focus of study for centuries. Aristotle: Influential Greek philosopher from 300s BC. Made arbitrary pronouncements about natural world Beliefs held throughout Middle Ages

5. Dueling Theories—17 th & 18 th Centuries Catastrophism: Sudden world-wide upheavals. Uniformitarianism: Processes occurring today also occurred in the past at about the same rate. James Hutton said "The present is the key to the past." Most widely accepted geologic theory today. Birth of modern geology as a science.

6. What Does it Mean to be a Science? 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

7. The Nature of Scientific Inquiry How or why things happen are explained using: Hypothesis – a tentative (or untested) explanation Theory – a well-tested and widely accepted view that the scientific community agrees best explains certain observable facts

8. The Nature of Scientific Inquiry, cont’d 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

9. Example of Transformation from Hypothesis to Theory Brief history of plate tectonics Early 20 th century-continents and oceans believed to be fixed features on the surface of the earth “Continental drift” hypothesis was proposed and ridiculed Over 50 years of research before hypothesis transformed into the theory of plate tectonics

10. Geologic Time Earth is approximately 4.6 billion years old Oldest rock on earth: 4.4 byo Relative ages based on fossil record Relative dating means that rocks are placed in their proper sequence or order without knowing their specific age Absolute ages based on isotopic dating

11. Geologic Time Magnitude of geologic time Involves vast times – millions or billions of years An appreciation for the magnitude of geologic time is important because many processes are very gradual

12. A View of Earth Earth is a planet that is small and self-contained Earth’s four spheres Hydrosphere Atmosphere Biosphere Geosphere

13. Earth as a System Earth is a dynamic planet with many interacting parts or spheres Earth System Science Aims to study Earth as a system composed of numerous interacting parts or subsystems Employs an interdisciplinary approach to solve global environmental problems

14. Earth as a System, cont’d What is a system? Any size group of interacting parts that form a complex whole Open vs. closed systems Feedback mechanisms Negative feedback – maintains the status quo Positive feedback – enhances or drives changes

15. Earth as a System, cont’d The Earth system is powered by the Sun that drives external processes in the Atmosphere Hydrosphere At Earth’s surface The Earth system is also powered by Earth’s interior

16. Earth’s Interior Layers defined by composition (density) Crust Mantle Core Layers defined by physical properties (strength) Lithosphere Asthenosphere Mesosphere Inner and outer core

17. Chemical Divisions of the Earth Crust Uppermost surface of the Earth Thinnest layer Largest variety of rock types Mantle Below the crust Composed of igneous and metamorphic rock Core Below the mantle Composed dominantly of iron with some nickel and other elements

18. Physical Divisions of the Earth Lithosphere Crust and strong part of upper mantle Makes up the tectonic "plates" of plate tectonics Asthenosphere Weak part of upper mantle Partially molten in some areas Lithosphere moves over this part of the mantle Mesosphere Lower mantle Stronger than asthenosphere

19. Physical Divisions of the Earth, cont’d Outer Core Liquid Composed of Fe with some Ni and other elements Inner Core Solid Same composition as outer core

20. The Face of Earth—the Crust Earth’s surface Continents Oceans Continents Mountain belts Most prominent feature of continents The stable interior Also called a craton – composed of shields and stable platforms

21. The Face of Earth, cont’d Ocean basins consist of Continental margins Deep-ocean basins Ocean ridge system

22. Ocean Basins Continental margins Includes the continental shelf, continental slope, and the continental rise Deep-ocean basins Abyssal plains Oceanic trenches Seamounts Oceanic ridge system Most prominent topographic feature on Earth Composed of igneous rock that has been fractured and uplifted

23. Major Types of Rocks Igneous rocks Sedimentary rocks Metamorphic rocks

24. Igneous Rocks Cooling and solidification of magma (molten rock) Examples include granite (intrusive) and basalt (extrusive)

25. Sedimentary Rocks Accumulate in layers at Earth’s surface Sediments are derived from weathering of preexisting rocks Examples include sandstone and limestone

26. Metamorphic Rocks Formed by “changing” preexisting igneous, sedimentary, or other metamorphic rocks Driving forces are heat and pressure Examples include gneiss and marble

27. The Rock Cycle The loop that involves the processes by which one rock changes to another Illustrates the various processes and paths as earth materials change both on the surface and inside the Earth

28. Demonstrate GEODe