The scientific method and the foundations of Geology

Goals To understand the basic scientific method as it applies to the Earth Sciences To cover some of the basic principals of the Earth Sciences

Siccar Point, Scotland Question?

The Scientific Method QUESTION: We want to know how some part of the Earth works. DATA COLLECTION: Observe, measure, describe, compile. HYPOTHESIS: A logical but tentative explanation that fits all the data collected and is expected to account for future observations.

It’s not “just a theory” TESTING: Testing, testing, and more testing. MODIFICATION: Hypotheses are modified to include the results of testing (see #4). THEORY: Our hypothesis now withstands rigor of all the testing (see #4) and consistently explains accumulating data. It is now a theory: A generally accepted explanation for a large set of diverse data and observations.

If a theory is really special... TESTING: Testing, testing, and more testing. SCIENTIFIC LAW: If a theory meets rigorous testing over a long period of time it may become a Scientific Law, like The Law of Gravity. PRINCIPAL: Generally a scientific law is so fundamental it provides the foundation of science.

How we develop and test hypotheses in the Earth Sciences Because we can’t fit the Earth in a test tube or sit and take notes for 20 m.y we use: Case studies of ancient features Remote sensing of the Earth’s interior Numerical and analogue simulations

We have learned that the Earth is very old (~4.5 billion years). So…. We have lots and lots and lots of time to work with. “The present is the key to the past”

Birth of modern Geology Principle of Uniformitarianism: Processes observed today have acted on the Earth over very long periods of time. So Observations of current geological processes can be used to interpret very old geologic events.

Other Important Geologic Principles Superposition: In any unaltered sequence of rock layers, each layer is younger than the one beneath it and older than the one above it.

Other Important Geologic Principles Superposition: In any unaltered sequence of rock layers, each layer is younger than the one beneath it and older than the one above it.

Original Horizontality: Sediments are deposited horizontally in layers that are parallel or nearly parallel with the Earth’s surface.

Think-pair-share activity 1.Come up with an every day analogue for the principal of original horizontality (preferably incorporating unhealthy food). 2.Compare, discuss, and refine your analogue with one or two of your neighbors. 3.Write up your results and pass them in.

Cross-Cutting Relationships: An igneous intrusion or geologic structure is always younger than the rock that surrounds it.

Siccar Point, Scotland Answer

1. Deposition 2. Tilting 3. Erosion 4. Deposition 5. Tilting 6. Erosion

Principle of Inclusion: Rock fragments contained within a larger body of rock are always older than the surrounding body of rock.

Basic rock types Igneous rocks: Crystallize (or freeze) from a melt Sedimentary rocks: Made up of particles (gravel, sand, clay) glued and pressed together Metamorphic rocks: Rocks that have recrystallized at high temperatures and pressures, but not melted.

The rock cycle