Time and Geology

1. Time and Geology

2. Relative Age Dating • In trying to understand the creation of the geology of an area prior to the 20th century techniques, a method referred to as Relative Age Dating was used. • Relative Age refers only to the order (i.e. older or younger) of particular events, not the actual age of an event. • Relative Age Dating is process involving the application of good observation skills and common sense to deduce the sequence of events in a particular area. True age is not relevant.

3. Principle of Original Horizontality • This principle is based upon the observation that sediment usually accumulates or is deposited in horizontal layers

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5. Principle of Superposition • This states that in a layered sequence of sedimentary rocks, the oldest layer is on the bottom and become progressively younger toward the top.

6. Principle of Lateral Continuity • This principle state that a layer of sedimentary rock or sediment extends laterally in all directions until it thins out or terminates

7. Principle of Cross-Cutting Relationship • Any event (e.g. fault: intrusions) that cuts through a rock or another event must be younger that the event it cuts through.

9. Principle of Inclusions • This states that inclusions (fragments of rock) of one rock found in another are always older than the rock they are found in.

11. The Principle of Faunal Succession • This principle proposes that fossil assemblages (groups of fossils) succeed one another through time in a regular and predictable order, from least complex to most complex.

12. So what has happened here? What is the oldest rock? What is the youngest rock?

18. The end result