Themes of the Day:

• History of the Science of Geology Cleanup
• The Scientific Method in Geology
• Origin of the Earth & Solar System
• Early Geologic History of the Earth

The Scientific Method in Geology - Drawn as a flow chart in class

• Observation
• Defining a Problem
• Creating a Hypothesis (educated guess)
• Testing the Hypothesis - direct tests in geology often hindered by issues of TIME and SCALE
  • By Experiments
  • By Modelling (where Time and Scale preclude direct testing)
  • By Evaluating Predictions
• Analyze Results of Tests
  • If tests confirm hypothesis - Go out and celebrate on Friday night. On Monday devise another test.
  • If tests refute hypothesis - Drown your sorrows on Friday night. Work through the weekend. Either scrap or modify hypothesis. Back to square one.
• Theory results from widely accepted, time-tested hypothesis (often applied to a group of related hypotheses)
• Laws and proofs are for math and physics - rarely encountered in geology.
• Paradigms - model of reality - a framework of hypotheses and theories that represent the best synthesis of the current understanding of a science
• Publish or Perish. For a couple of really insightful essays on the scientific method, take the time to read Whatever Happened to Cold Fusion? and How Science Works (PDF format) by David Goodstein. On a lighter note, here's a guide on How To Write A Scientific Paper from the Annals of Improbable Research (AIR).

Origin of the Earth & Solar System

• Big Bang ~12-15 Ga (billion years ago) - chemical elements created in star systems prior to our own
• Nebular Hypothesis - Sun and planets of our solar system condensed from a cosmic dust cloud ~4.6 to 4.5 Ga
• Early Earth was undifferentiated (homogeneous) material similar to average solar system composition
• Early Earth was extremely hot (gravitational potential energy of nebular dust becomes kinetic energy and finally thermal energy as Earth condenses)
• Core formation as molten iron separates from molten silicates and sinks to the center of the planet due to its high density (vinegar and oil analogy)
• Soon after core formation a Mars-sized body collides with the molten Earth spraying material that will become the Moon into Earth orbit
• Meteor bombardment intense on early Earth - crust, oceans, and atmosphere develop slowly
• Most of the evidence for this stage of Earth's history comes from meteorites and lunar samples

Early Geologic History of the Earth

• Age of the Earth ~4.6 to 4.5 Ga (billion years old) - equivalent to formation of our solar system
• Oldest terrestrial mineral ~4.4 Ga (zircon, western Australia); Oldest surviving rocks on Earth ~4.0 Ga (Acasta gneiss - northern Canada)
• Earliest fossil evidence for life (single celled organisms) ~3.5 Ga
• Cambrian explosion (rapid diversification of multicelled organisms) ~570 Ma (million years ago)
• Geologic time scale - many subdivisions since ~500 Ma reflect a preservational bias in the geologic record