EES 105-A01




A. Geology: the study of Solid Earth

B. Two Broad Areas:

– Physical Geology: material & processes

– Historical Geology: origin of Earth,

development through time

C. Why study geology:

  • natural resources

  • natural hazards

  • environmental issues & human impact

  • population issues (demand on resources)

How old is the Earth?

A.Historical Perspectives:

mid-1600: James Ussher, Archbishop of Ireland

17th/18th centuries: the doctrine of catastrophism

Late 18th century: James Hutton, Theory of the Earth(1795)

the physical, chemical, and biological laws that operated today also operated in the geologic past”

19th century: Sir Charles Lyell advocated the idea

Principles of Geology (1830-1833)

William Whewell first used the term uniformitarianism (1832)

Uniformitarianism: one of the most important unifying concepts in the geosciences

“The present is the key to the past.”

B. Geological Time:

– Relative Dating: Law of superposition

Principle of fossil succession

– Absolute Dating: radioactive nuclides

– The Geologic Time Scale (Fig. 1.9)

C. Modern View:

– How old is the Earth: 4.5 billion years

– The Geologic Time Scale

  • 12%: Phanerozoic

  • 88%: Precambrian

  • 540 MYA: border between phanerozoic/precambrian

  • 250 MYA: border between paleozoic/mesozoic

Scientific Inquiry

A. Objectives of Science:

    1. To discover the fundamental patterns of the natural world

    2. Use the knowledge to predict

B. An idea can become a:

  1. Hypothesis: untested, tentative explanation

  2. Theory: tested and confirmed

C. Scientific Method:

  1. Gather facts through observations

  2. Formulate hypotheses

    1. Test hypotheses: through experiments OR observations

    2. Acceptance/modification/rejection of the hypotheses

A View of Earth

A. Earth in Space: a blue planet

  1. Hydrosphere:71% water, avg depth 3800m

  2. Atmosphere:90% within 16km; .001% of water

  3. Biosphere:

  4. Solid Earth:mean radius ~6371km; mean height 875m

B. Earth as a System:

System: a group of interacting parts


The Earth System is powered by:

  • Solar radiation

  • Earth interior heat

Feedback Mechanisms : Positive: icemelt – expose soil

Negative: cloud – reflect sunlight

Earth’s Interior Structure

A. Three Zones by Composition:

1. Crust: oceanic (basalt) ~7km

continental (granitic basaltic)

35-40km; up to 70km in mtn.

2. Mantle: peridotite

3. Core: iron-nickel alloy

B. Layers Defined by Physical Properties:

  1. Lithosphere : crust and outermost mantle, rigid

  2. Asthenosphere: upper mantle beneath the crust, weak & plastic

  3. Mesosphere: lower mantle

  4. Inner and Outer Core





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