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1 Chapter 1 Earth System History. 2 Study of the inter- connected physicochemical and biological changes that our planet has experienced over the course.

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Presentation on theme: "1 Chapter 1 Earth System History. 2 Study of the inter- connected physicochemical and biological changes that our planet has experienced over the course."— Presentation transcript:

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 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 4 Earth Systems History Earth is an Archive –Geologic record archives Earth’s history –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 Actualism –Application of modern processes to ancient system –Popularized by Charles Lyell James Hutton Charles Lyell

6 6 Actualism Modern ripples provide clues to ancient systems.

7 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 8 Materials and Processes Rock –I–Interlocking or bonded grains of matter typically composed of single minerals Mineral –N–Naturally occurring inorganic solid element or compound with a particular chemical composition or range of compositions and a characteristic internal structure Outcrop –R–Rocky surfaces that stand exposed and are readily accessible for study

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

10 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 11 Igneous Rocks Extrusive igneous rocks –harden at the earth’s surface Intrusive igneous rocks –harden within the earth

12 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 13 Formed from: –Preexisting rocks (clastic rocks) Sandstone Shale –Skeletal debris Limestone –Chemical precipitates Evaporates Sedimentary Rocks

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

15 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 16 Rock Units Formations –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 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 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 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 20 Unconformity Substantial interval of time when erosion occurred rather than deposition

21 21 Unconformity –Angular unconformity –Disconformity –Nonconformity

22 22 Angular Unconformity

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

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

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

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

27 27

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

29 29 Spreading Zones Plates move apart Mid-ocean ridge

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

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

32 32

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

34 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 35 The Six Mass Extinctions 1 2 3 4 5 6

36 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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