Introduction to Earth Science/GeologyC. Ophardt

• Geology, What is it?• Geology is the study of the Earth. • Includes surface process which have shaped

the earth's surface• Study of the ocean floors• Interior of the Earth. • History of the Earth as it has evolved to its

present condition.

• The Earth has changed throughout its history, and will continue to change (Unifying Theme)

Earth Science/Geology - Time Scale

• Time scale (Unifying Theme)• Earth is about 4.6 billion years old• Human beings - maybe 2 million years.• Humans have witnessed only 0.043% of

Earth history• How can we think about changes on earth on

a scale of billions of years?

Earth Science/Geology - Time Scale II

• Try to imagine 1 million years• That's 50,000 times longer than you have

lived.• A river deposits about 1 mm of sediment

(mud) each year. • How thick is the mud after 100 years? • -- 10 cm hardly noticeable over your lifetime. • What if the river keeps depositing 1 mm/yr 

for 10 million years?       • Answer 10,000 meters (6.2 miles).

Scientific Method - Inquiry in Earth Science

• Strongly tied to experiment and observation.• Observations can be cast as experiments --

thought experiments.• Observation: Wind River Mountains in

Wyoming - 10,000 feet above sea level -observe a rock containing many seashells.

• How did it get there?

• Questions:• Was area covered by an ocean at some time

in the past? • Was this ocean 10,000 feet deep? • Was this area at one time at sea level and

unknown forces elevated it to its present elevation?

• Tie in to previous slide about rate of deposition.

Scientific Method - Inquiry in Earth Science

Inquiry in Earth Science III

• Hypothesis:• The observation leads to several hypotheses • Attempt to explain the observation. • Formulation of a tentative explanation is not

sufficient• What additional information may be needed in

order to "prove" the hypothesis?• New information may modify the original

explanation or cause it to be discarded.

Inquiry in Earth Science IV• Theory: Principle of Uniformitarianism -

Slow Changes• Processes that are operating at present are

the same processes that have operated in the past.

• “Present is the key to the past.” • Look at processes that occur today,   • Infer that the same processes operated in the

past.• Key Assumption - Laws of nature have not

changed through time.

Inquiry in Earth Science IV

• Theory: Principle of Catastrophism: - Fast Changes

• Major changes in Earth’s crustal layers result from catastrophic events

• Floods

• Massive Volcanism

• Massive Earthquakes

• Changes were sporadic• Key Assumption - Laws of nature are the

same but the rate of change is not

Earth Materials and Processes• Slow processes• Formation of rocks • Chemical breakdown of rock to form soil

(weathering) • Chemical cementation of sand grains

together to form rock (diagenesis) • Recrystallization to rock to form a different

rock (metamorphism) • Build mountain ranges (tectonism) • Erosion of mountain ranges

Earth Materials and Processes• Fast Processes • Beach erosion during a storm. • Construction of a volcanic cone • Landslides (avalanches) • Dust Storms • Mudflows• Earthquakes

Structure of the Earth• Crust - variable thickness and composition • Continental 10 - 50 km thick • Oceanic 8 - 10 km thick • Mantle - 3488 km thick, made up of a rock

called peridotite

• Core - 2883 km radius, made up of Iron (Fe) and small amount of Nickel (Ni)

Structure of the Earth

Structure of the Earth- Hydrosphere

• Water sphere includes all the earth's water found in streams, lakes, the soil, groundwater, and in the air.

• Water of hydrosphere is distributed: oceans, lakes, streams.

• Water is found in vapor, liquid and solid states in the atmosphere.

• Biosphere - interface between the spheres water moves between hydrosphere, lithosphere and atmosphere by plant transpiration.

Hydrologic Cycle

Atmosphere

• Atmosphere is a dynamic mixture of gases that envelop the Earth.

• Two gases, nitrogen and oxygen make up most of the atmosphere by volume.

• Minor gases include have a significant impact on heat budget and the moisture across the Earth. Water vapor, Carbon dioxide

• Atmosphere has a layered structure as defined by vertical temperature changes.

Structure of the Earth

• Lithosphere

• Outer rigid part of earth includes the crust and upper part of the mantle.

• Act as a unit and respond similarly to mechanical deformation.

• 60 miles in thickness to 150 miles thick beneath continents.

Structure of the Earth• Asthenosphere• Lies beneath the lithosphere• Extends to a depth of about 400 miles. • A small amount of liquid (from partial melting

of the upper mantle) in upper 100 miles• Detached from the underlying asthenosphere. • Capable of flowing - convective.

Structure of the Earth

• Mesosphere - about 2500 km thick, solid rock, but still capable of flowing. Another name is Mantle.

• Outer Core - 2250 km thick, Fe and Ni, liquid

• Inner core - 1230 km radius, Fe and Ni, solid

• All of the above is known from the way seismic (earthquake waves) pass through the Earth

Quiz Questions• Ques. 1: The earth formed:• A. 455 million years ago.• B. 0.455 billion years ago• C. 4,550 million years ago • D. 45.5 billion years ago

Ques. 2: Catastrophism could be use to explain:• A. the formation of Grand Canyon.• B. the evolution of the coastal area near Siccar

Point, Scotland• C. the presence of blue algae in stromatolites.• D. the iridium-rich layer observed around the world

at the K/T boundary.

Quiz Questions• Ques. 3: The mesosphere is located between: • A. the solid inner core and the liquid outer core• B. the liquid outer core and the asthenosphere• C. the lithosphere and the asthenosphere• D. the crust and the asthenosphere

Ques. 4: To a close approximation, the term that best describes the Earth system is:

• A. an open system• B. a closed system• C. an isolated system• D. an insulated system

Quiz Questions• Ques. 5: The lithosphere is best described as:

A. a stiff and rocky layer within the Moho region.• B. a rigid layer found upward from the

asthenosphere.• C. a rigid layer found downward from the

asthenosphere.• D. a rigid and rocky layer capable of flowing

Ques. 6: What are the Earth's "four spheres"? How do they interact?

Ques. 7: What is the difference between catastrophism and gradualism or uniformitarianism? Can you cite an example of each?

Quiz Questions

• Ques. 8: What are the key physical properties of the inner core, outer core, mesosphere, asthenosphere, and lithosphere?

Citations

• http://www.tulane.edu/~sanelson/geol111/index.html

• http://www.uh.edu/~jbutler/physical/onlinespring20011.html