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Chapter 1 Earth System History.

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Presentation on theme: "Chapter 1 Earth System History."— Presentation transcript:

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 Extinctions
1 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

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