GES 101 Introductory Lectures Handout

Evolutionary course of a planet is largely governed by its initial state.

Difficult to learn about Earth's initial state because
- Earth is large
- Earth is dynamic
- Earth is old
- only 1 Earth

New view of Earth in past 30 years.
- space exploration
- plate tectonics

Universe
- created in big bang
- 11 billion years ago
- stars most important bodies in universe ephemeral evolutionary course depends on mass Solar System
- 5 billion years old
- Schmidt hypothesis
- cold accretion
- Sun is middle-age star
- regularity suggests all bodies of solar system formed at same time

Our explanation for origin of solar system raises following questions:
1. What happened during 1st billion years of Earth history?
2. Why does Earth's surface look different than surfaces of other planets?
3. When and why did Earth differentiate?
4. When did ocean and atmosphere evolve?
5. If oldest rx on Earth are 3.9 billion years old, how do we know Earth is 4.6 billion years old?

Lunar Exploration
a. highlands contain 4.4 billion years old rx
b. heavy meteorite bombardment ceased 3.8 billion years ago
c. moon was largely molten 4.2 billion years ago

THEME: Earth's Internal Heat Engine CLAIMS:
a) Earth accreted "cold"
b) if Moon was molten early in its history, so was Earth
c) today Earth is differentiated
d) Earth is cooling down (core "freezing")

QUESTIONS:
a) Where did the heat to melt the EARTH come from?
b) When and why did Earth differentiate?
c) How is Earth cooling down?

OUTLINE

conversion of K.E. to heat on impact
adiabatic
self-compression
Earth's Internal Heat
fossil
radioactive decay
Buildup of Internal Heat - differentiation
radiation
Earth
cooling
-convection
-conduction
Plate tectonics = sea-floor spreading and continental drift
Driving force for P.T.?
divergent Plate Boundaries
-convergent
-transform
Continents grow over time at expense of mantle

 
Review Questions Introduction & Overview
1. Geologists' understanding of Earth processes has changed dramatically during the past three decades. Identify and briefly discuss two significant developments which have revolutionized the way geologists view the Earth.

2. Briefly outline the Schmidt hypothesis (variant of the nebular hypothesis) for the formation of our solar system. Include information about the age of the solar system and identify the forces operating on the nebula.

3. The planets in our solar system are divided into two groups (terrestrial and Jovian). a. Briefly describe the composition and density of each group, and b. Explain how these differences originated.

4. Identify and briefly describe the Earth's major compositional layers. How and when did the Earth differentiate? Use a labeled cross-section of the Earth to illustrate your answer.

5. Explain why rocks older than 4.0 billion years have not been found on Earth even though 4.6 billion-year-old meteorites and lunar rocks exist.

6. Ancient meteorite craters are numerous on the Moon and on Mars yet very rare on Earth. Were meteorite craters ever numerous on Earth? If so, when in the past were they more numerous? Why are craters on Earth so rare today?

7. Identify and briefly discuss the processes which have contributed to the Earth's internal heat.

8. Briefly explain how convection and conduction cool the Earth. Which mechanism is most efficient?

9. What is plate tectonics? Name and briefly discuss the three types of edges that bound lithospheric plates. (Hint: use a labeled diagram to illustrate your answer).

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