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November 2,2011. Objective: To learn how geologists infer the logical sequence of events and establish a probable relative age for a series of rock layers. Agenda: Law of superposition notes Text book questions Page 204-205 answer questions 4,12,13 Geologic Timeline hanging
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Objective: • To learn how geologists infer the logical sequence of events and establish a probable relative age for a series of rock layers • Agenda: • Law of superposition notes • Text book questions • Page 204-205 answer questions 4,12,13 • Geologic Timeline hanging • Lab: Law of Superposition
Discovering Earth’s History • Principle of Uniformitarianism: • The forces and processes happening today have been going on for a long time
Key Principles • Relative Dating • Tells us the sequence in which events occurred • Law of Superposition • In sedimentary rocks, each bed is older than the one above it and younger than the one below it
Law of Superposition • Younger Layers→ • Older Layers→
Relative Dating—Key Principles Principle of Cross-Cutting Relationships • The principle of cross-cutting relationships states that when a fault cuts through rock layers, or when magma intrudes other rocks and crystallizes, we can assume that the fault or intrusion is younger than the rocks affected.
Relative Dating—Key Principles Unconformities • An unconformity represents a long period during which deposition stopped, erosion removed previously formed rocks, and then deposition resumed.
Relative Dating—Key Principles Unconformities • A break in the geologic record created when rock layers are eroded or when sediment is not deposited for a long period of time.
Correlation of Rock Layers or walking the outcrop Correlation is establishing the equivalence of rocks of similar age in different areas.