This series of lectures will focus on the following objectives:

• understanding what geology is, and its varies disciplines
• Intoducing the Earth's dynamic system, internal structure, and the
• general physical features of the Earth's surface
• introduce the concept of geologic time and the age of the Earth

Assignments

1. Earth: Chapter 1 - Introduction to Geology
2. Earth Revealed: movies. (http://www.learner.org/resources/series78.html)  Requires Windows media Player.  Sign in and view films 1,2,3,4,26.

Terms: Abyssal plain, asthenosphere, atmosphere, biosphere, catstrophism, continental margin, continental shelf, sontinental slope, core, crust, deep-ocean trench, geology, geosphere, historical geology, hydrosphere, hypothesis, igneous rock, inner core, lithosphere, mantle, metamorphic rock, negative feedback, oceanic ridge, outer core, physical geology, positive feedback mechanisms, relative dating, rock cycle, sedimentary rock, superposition, theory, uniformitarianism

What is Geology?

Geology is the scientific investigation of the Earth. The Earth system includes four interacting realms: the geosphere, hydrosphere, atmosphere, and biosphere.  Traditionally geology is divided into Physical geology, dealing with composition, features and dynamic processes of the physical earth, and Historical geology, which focuses on the origin and evolution of the Earth through time.

Why study Physical Geology?

NATURAL HAZARDS: The early 20th Century historian and philosopher Will Durant once wrote "Civilizations exists by geologic consent--subject to change without notice."  Of the many geologic disasters, such as earthquakes, floods, landslides and tsunami, volcanic eruptions are the most notorious for there effect on humanity. (See table below.) Some hazards may not appear to be geologically linked but in fact are.  Hurricane Katrina is a case in point.  According to the United States Geological Survey (Louisiana Coastal Land Loss), Louisiana is loosing 35 square miles of land every year through coastal erosion and subsidence.   Since 1932 the amount of land loss (1,900 square miles) approximates the size of the state of Delaware. An additional 700 square mile could be lost in the next 50 years.  Beaches, marshes, and reefs are natural buffers to wave energy and protect the coast.  When these are removed by erosion coastal communities are placed at risk and the effects of coastal Hurricane worsens. New Orleans was build on the Mississippi Delta composed of compacting and subsiding soft water-rich sediments--already an unstable environment.   Replenishing and protective sediment is directed offshore as artificial levees and other engineered structures try to keep the Mississippi in place -- a lose-lose situation. Land loss is a geologic issue.

RESOURCES: How does geology influences your daily activities? Let's face it everything we eat and use comes from the Earth. Some geologic resources and their derivatives are water, fuel, soil (food), minerals (gems,metals, glass, mineral nutrients, cosmetics, wallboard), rock (construction aggregate, sand and gravel, building stone), petroleum byproduct (plastics, fabrics). Life forms are a byproduct of earth processes. Our survival as well as economic stability is intrinsically linked to our geologic environment.

ECOSYSTEMS: How does geology influence habitat and biodiversity?

What is Science?

1. collecting data and making observations (facts)
2. proposing multiple hypotheses to explain the data and observations
3. exhaustive testing. Hypotheses that do not hold up are thrown out or modified.
4. using the hypothesis to make accurate predictions.
5. A hypothesis that has not been disproved after thorough testing is elevated to theory status. A theory is not untested conjecture!
   Read: The Truth Behind Noah's Flood (BBC Scientific American Frontiers) Would you say this is a hypothesis or theory? What has yet to be determined?

Important concepts in geology

Catastrophism is the belief that features on the earth are shaped by short term catastrophic events.  The belief was popular among biblical scholars who believed that the earth was created in 4004 BC, a date obtained by James Ussher, the Archbishop of Armagh. 

Uniformitarianism, developed by the Scottish physician James Hutton in the late 1700's, is the belief that features are created through everyday processes acting at slow rates throughout millions of years, and that these processes have been active throughout earth history.  Therefore by observing processes in operation today we can interpret features of the past.

Introduction to the Earth's Systems

Online resource:  Earth's Interior & Plate Tectonics (http://www.solarviews.com/eng/earthint.htm) by Rosanna L. Hamilton. From Views of the Solar System by Calvin J. Hamilton

• The Earth is dynamic system is driven by internal and external source of energy:
  • HEAT and GRAVITY > CONVECTION :
    • Solar energy (Drives the hydrologic cycle and all surficial processes such as such as weathering, erosion, stream flow, glacial flow, oceanic circulation, climate, etc.)
    • Geothermal energy produced from the crystallization of the iron core and decay of radioactive elements (Drives plate tectonics >volcanism, earthquakes, etc)
• The Earth is composed of at least four interacting systems:
  • Atmosphere - outer gaseous sphere
  • Hydrosphere-Cryosphere - region within the earth where meteoric water ciriculates
  • Biosphere-Anthrosphere - region where life exists and a major force
  • Solid Earth (Geosphere) - lithosphere to the core
    Read: Abrupt Climate Change: Should We Be Worried?  How are these systems linked? Why is understanding the interactions between the solid earth, atmosphere, hydrosphere, and biosphere important to deciphering climate change, and our response to it?
    

The Earth's Internal Structure

• Internal layers of the Earth (USGS <http://pubs.usgs.gov/publications/text/inside.html>): These layers have varying compositions, densities, and temperatures that influence their mechanical properties. The approximate depths at which these layers occur is given in kilometers.

Crustal types and their significance

• Continental Crust:
  • High in SiO₂ (65 -75%: silicic or granitic)
  • Relatively thick (up to 50 km)
  • lower in density (2.7 g/cm³)
  • Oldest rocks are 3.8 by
• Oceanic Crust:
  • Less SiO₂ (±50-60%: mafic or basaltic)
  • Relatively thin (± 8 km)
  • higher in density (3 g/cm³)
  • typically <200 my in age
• Significance of the two types of crust
  1. Thickness and density control the large-scale variations in surface elevation: Hence the presence of continents and ocean basins.
  2. The denser oceanic crust is constantly recycled through subduction and sea-floor spreading
  3. More buoyant continental crust, which is not subducted, is recycled by processes that operate on or near the surface

The rigid outer layer of the Earth containing both the crust and outer mantle is call the lithosphere. The plates that move about Earth's surface include the entire lithosphere, not simply the crust.

Question: Never having drilled more than a few miles through the crust, how do geoscientists learn about the interior of the Earth?

Features of the Earth's Surface

Features beneath the oceans

1. Mid-oceanic ridges and rises (with axial rift valleys) - ophiolites
2. Deep-sea trenches
3. Abyssal plain (floor)
4. Abyssal hills
5. Continental rise
6. Hot spot volcanic chains
7. Volcanic island arcs

Continental Features

1. Stable craton (wikipedia)
2. Shield
3. Platform
4. Mountain belts (orogenic belts)

Continental margins

Types

1. Passive: The margin does not lie along an active plate margin. Example: East Coast of North America.
2. Active: Lies along an active plate margin.

Example: west coasts of North and South America

Features

1. Continental Shelf
2. Continental Slope

 Introduction to Geologic Time

Explore the Web Time Machine (UCMP Exhibit Halls, University of California, Berkeley <http://www.ucmp.berkeley.edu/help/timeform.html>)

The earth is 4.6 billion years old. 

The dinosaurs lived on the earth for over 150 million years. So far the existence of man on earth has been less than 3 million years.

Mountain ranges are created and destroyed hundreds of times over the course of geologic time by processes that are barely perceptible in our lifetime. A Geologist views events in terms of geologic time, not human time.

My Geologic Time Analogy: Imagine you have 4.6 roles of 1000-sheet Scott toilet paper. Let's say each sheet equals one million years. The first four roles represents the Precambrian, the time before the development of abundant life forms. The last two and one half to three sheet on the last role (the Phanerozoic) represents the time span of the human species on earth.