Lecture Outlines

Physical Geology, 15/e

•Plummer, Carlson & Hammersley

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Introducing Geology, the Essentials ofPlate Tectonics, and Other ImportantConceptsPhysical Geology 15/e, Chapter 1

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Who Needs Geology?

•Geology—the scientific study of Earth• Physical geology

• the study of Earth’s materials,

• changes of the surface and interior of the Earth,

and the forces that cause those changes

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Supplying Things We Need

• Nonmetals (rock, clay, salt etc…)

• ~7600 kg/person/year

• Metals

• ~337 kg/person/year

• Energy

• 3430 (906 gallons) literspetroleum

• 2570 kg coal

• 2389 cubic meters natural gas

• 0.1 kg of uranium

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Who Needs Geology?

Resources needed to make a wooden pencil

Protecting the Environment

• Understanding geology canhelp us lessen or preventdamage to theenvironment—just as it canbe used to find the resourcesin the first place.

• Dwindling resources canencourage disregard forecological damage caused byextraction activities.

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Who Needs Geology?

The Alaskan Pipeline

Avoiding Geologic Hazards

Earthquakes, volcanic eruptions, landslides, floods and tsunamisare the most dangerous geologic hazards.

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Who Needs Geology?

Damage in Haiti following earthquake of 2010 Damage in Chili following earthquake of 2010

Avoiding Geologic Hazards

• Volcanoes - eruptions oflava and ash canoverwhelm populatedareas and disrupt air traffic

• Mudflows, landslides,

floods, and wave erosion

Understanding OurSurroundings

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Who Needs Geology?

Mount Pinatubo

Atmosphere—the gases that envelop the Earth

Hydrosphere—water on or near the Earth’ssurface, such as the oceans, rivers, lakes andglaciers

Biosphere—all living or once-living materials

Geosphere—the solid rocky Earth

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Earth Systems

Internal — heat moving from hotinterior of the Earth to the coolerexterior

• Drives volcanoes, earthquakes andmountain building

External — energy from the Sun

• Drives atmospheric and oceaniccirculation

• Controls weathering of rocks atEarth’s surface

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An Overview of Physical Geology –Important Concepts

Internal Processes: How the Earth’s Internal Heat EngineWorks

Earth’s Interior

Three Major Concentric Zones

•Crust – outermost very thin rocky

shell (oceanic and continental)

•Mantle - hot solid that flows slowly

over time; (most voluminous of Earth’slayers)

•Core – innermost zone of the Earth

Outer Core – liquid iron and nickel

Inner Core – solid iron and nickel

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An Overview of Physical Geology –Important Concepts

Earth’s Interior (cont.)

• Lithosphere

• Rigid/brittle outer shell ofEarth

• Composed of both crust anduppermost mantle

• Makes up Earth’s tectonicplates

• Asthenosphere

• Plastic zone on which thelithosphere floats

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An Overview of Physical Geology –Important Concepts

Theory of Plate Tectonics

•Continental Drift Hypothesis• Originally proposed in early 20th century by Alfred Wegener to explain the

“fit of continents,” matching rock types and fossils across ocean basins, etc.• Insufficient evidence found for driving mechanism; hypothesis initially

rejected

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An Overview of Physical Geology –Important Concepts

• Plate Tectonics Theory• Originally proposed in the late 1960s• Included new understanding of the sea-

floor and explanation of driving force• Describes lithosphere as being broken

into plates that are in motion• Explains origin and distribution of

volcanoes, fault zones, and mountainbelts

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An Overview of Physical Geology –Important Concepts

The Theory of Plate Tectonics (cont.)

• Divergent boundaries• Plates move apart

• Magma rises, cools and forms newlithosphere

• Typically expressed as mid-oceanicridges

• Convergent boundaries• Plates move toward each other

• Ocean-Continent

• Ocean-Ocean

• Continent-Continent

Ocean to continent convergent boundary

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An Overview of Physical Geology –Important Concepts

The Theory of Plate Tectonics (cont.)

• Transform boundaries• Plates slide past one another

• Fault zones, earthquakes mark boundary

• San Andreas fault in California

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An Overview of Physical Geology –Important Concepts

Surficial Processes: The Earth’s External Heat Engine• Isostatic Adjustment/Uplift

• Volcanic and/or tectonic forces build crust up above sea level• Removal of material by erosion allows isostatic uplift of underlying rocks

• Weathering and Erosion• Rainfall and glaciers flow down slopes• Moving water, ice and wind loosen and erode geologic materials, creating

sediment

• Deposition• Loose sediment is deposited when transport agent loses its carrying power• Earlier sediments get buried and harden into sedimentary rock

• Deep Time• Most geologic processes occur gradually over millions of years

• Changes typically imperceptible over the span of a human lifetime

• Current best estimate for age of Earth is ~4.55 billion years

• Geologic Time and the History of Life• 541 million years: complex life forms first became abundant

• 230 million years: reptiles became abundant

• 66 million years: dinosaurs became extinct

• 5 million year: humans

Nothing hurries geology— Mark Twain

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Geologic time

End of Chapter 1

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