1. 1 Chapter 1 Earth System History

2. 2 Study of the inter- connected physicochemical and biological changes that our planet has experienced over the course of geologic time

3. 3 Guiding Questions What fundamental principles guide geologists as they reconstruct Earth’s history? What are the basic kinds of rocks and how are they interrelated? How do geologists unravel the age relations of rocks? How does the lithosphere relate to Earth’s inner regions, and how does it move and deform?

4. 4 Earth Systems History Earth is an Archive –Geologic record archives Earth’s history –Results from the interaction of complex systems within the planet

5. 5 Foundations of Geology Principle of Uniformitarianism –There are inviolable laws of nature that have not changed in the course of time –First founding principle of geology James Hutton Actualism –Application of modern processes to ancient system Catastrophism

6. 6 Actualism Modern ripples (A) provide clues to ancient systems (B)

7. 7 Materials and Processes Rock –Interlocking or bonded grains of matter typically composed of single minerals Mineral –Naturally occurring inorganic solid element or compound with a particular chemical composition or range of compositions and a characteristic internal structure Outcrop/Exposure –Rocky surfaces that stand exposed and are readily accessible for study

8. 8 Rock Cycle Surface and internal processes link materials to form three rock types: –Igneous –Sedimentary –Metamorphic

9. 9 Igneous Rocks Formed by cooling of molten material to the point of hardening –Composed of interlocking grains, each consisting of a particular mineral Magma –Molten material that solidifies into igneous rock

10. 10 Igneous Rocks Extrusive igneous rocks –Hardens at the Earth’s surface Intrusive igneous rocks –Hardens within the Earth

11. 11 Sedimentary Rocks Sediments –Material deposited on Earth’s surface by water, ice, or air –Weathering Collective term for chemical and physical processes that break down rocks at Earth’s surface –Erosion Processes that loosen pieces of rock and move them downhill

12. 12 Formed from: –Pre-existing rocks Sandstone Shale –Skeletal debris Limestone –Chemical precipitates Evaporates Sedimentary Rocks

13. 13 Sedimentary Rocks Stratum: –Tabular layer of sediment accumulated in discrete episodes –Bed

14. 14 Metamorphic Rocks Formed by the alteration of preexisting rocks under high temperatures and pressure Alteration occurs without melting rocks

15. 15 Rock Units Formations –Unit of rock formed in a particular way –Formally named, often for nearby geographic feature Kaibab Limestone (Rim of the Grand Canyon) Member –Smaller rock unit Group –Groups of formations

16. 16 Steno’s Principles Principle of Superposition –Oldest strata are at the bottom in an undisturbed sequence of strata Principle of Original Horizontality –All strata are horizontal when they form Principle of Original Lateral Continuity –Strata originally are unbroken flat expanses –Interrupted by erosion

17. 17 Cross-cutting Relationships Principle of Intrusive Relationships –Intrusive igneous rocks are always younger than the rock they invade Principle of Components –Fragments within a second body of rock are older than the second body of rock

18. 18 Fossils Remnants of ancient life, thousands to millions of years old Fossil succession –Date by comparing them to fossils throughout the world –William Smith

19. 19 Geologic Time Scale Developed using –Biostratigraphy (fossil succession) –Radioactive decay Divided into –Phanerozoic –Precambrian/Archean Cambrian –Oldest rocks with conspicuous fossils

20. 20 Earth’s Interior Crust Mantle Core –Moho Crust/mantle boundary Lithosphere Asthenosphere

21. 21 Plate Tectonics Crust –Oceanic mafic –Continental felsic

22. 22 Plate Tectonics Movement of lithospheric plates Plates formed at spreading centers, destroyed at trenches Driven by convection

23. 23 Convection Material heated deep in the asthenosphere rises to displace cooler, denser material nearer the surface

24. 24 Spreading Zones Plates move apart Mid-ocean ridge

25. 25 Subduction Zones Trenches Associated with volcanoes –Partial melting of upper mantle

26. 26 Water Cycle Water –Abundant –High heat capacity Water cycle –Exchange between reservoirs Atmosphere Biosphere Hydrosphere Groundwater

27. 27 Directional Changes Evolution - the changing of organisms that constitute biosphere is a one-way process. Cooling - the Earth’s internal temperature is slowly decreasing.

28. 28 Unconformity Substantial interval of time when erosion occurred rather than deposition

29. 29 Unconformity –Angular unconformity –Disconformity –Nonconformity

30. 30 Evolution Extinction Mass extinctions –Global catastrophes in which a large percentage of species disappeared