1. Chapter 1
Earth System History

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

3. Guiding Questions
What fundamental principles guide geologists as they reconstruct Earth’s history?
What are the basic kinds of rock 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. Earth Systems History Earth is an Archive
Geologic record archives Earth’s history
Interaction of complex systems within the planet

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

6. Actualism
Modern ripples provide clues to ancient systems.

7. Catastrophism
Earth forms (mountains, Grand Canyon, rock layers, fossils found high in the mountains) were due to catastrophic forces that shaped the world in a relatively short time.
Leads to ‘Young Earth’ concept
Bishop James Ussher of Ireland
October 26, 4004 BC, 9:00 am
~6000 years

8. 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
Rocky surfaces that stand exposed and are readily accessible for study

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

10. Igneous Rocks
Formed by cooling of molten material to the point of hardening
Composed of bonded grains, each consisting of a particular mineral
Magma
Molten material that turns into igneous rock

11. Igneous Rocks Extrusive igneous rocks Intrusive igneous rocks
harden at the earth’s surface
Intrusive igneous rocks
harden within the earth

12. 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

13. Sedimentary Rocks Formed from: Preexisting rocks (clastic rocks)
Sandstone
Shale
Skeletal debris
Limestone
Chemical precipitates
Evaporates

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

15. Metamorphic Rocks
Formed by alteration of preexisting rocks under high temperatures and pressure
Alteration occurs without melting rocks
Density increases
Crystals enlarge
Lineation of some minerals

16. Rock Units Formations Member Group
Unit of rock formed in a particular way
Formally named, often for nearby geographic feature
Catskill Formation
Member
Smaller rock unit
Group
Groups of formations

17. 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

18. 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

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

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

21. Unconformity
Angular unconformity
Disconformity
Nonconformity

22. Angular Unconformity

23. Geologic Time Scale Developed using Divided into Cambrian
Biostratigraphy (fossil succession)
Radioactive decay
Divided into
Phanerozoic
Precambrian/Archean
Cambrian
Oldest rocks with conspicuous fossils
See p. 12

24. Earth’s Interior Crust Mantle Core Lithosphere Asthenosphere
Mohorovicic Discontinuity (Moho)
Crust/mantle boundary
Lithosphere
Asthenosphere

25. Plate Tectonics Crust Oceanic Continental Mafic (Mg- and Fe- rich)
Felsic (Si-rich, lower in Mg and Fe)

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

28. Convection
Material heated deep in asthenosphere rises to displace cooler less dense material nearer the surface

29. Spreading Zones
Plates move apart
Mid-ocean ridge

30. Mid-Atlantic Ridge, a spreading zone
The land of fire and ice
Mid-Atlantic Ridge, a spreading zone

31. Subduction Zones Trenches Associated with volcanoes
Partial melting of lithosphere
Animations

33. Hydrological (Water) Cycle
Abundant
High heat capacity
Water cycle
Exchange between reservoirs
Atmosphere
Biosphere
Hydrosphere
Groundwater

34. Evolution
The process by which particular forms of life give rise to other forms by way of genetic changes.
Natural selection
Primary mechanism of evolution
Process operates on heritable variability, selection results from differences among individuals in longevity and production of offspring
Extinction
Mass extinctions
Global catastrophes in which large percentage of species disappeared

35. The Six Mass Extinctions1 3 5 4 6 2

36. Directional Changes in Earth’s History
Initial views of Earth
Internal energy
Solar energy
Evolution of life
Life shapes environment and vis versa (reducing to oxydizing atmosphere
Episodic changes (External and Internal causes)
Asteroid impacts
Milankovitch
Earthquakes
Sedimentation
Extinctions