EARTH 7 Lecture Notes - Lecture 3: Nicolas Steno, James Hutton, Siccar Point
10/5/17
● Where to look for dino fossils
○ The right type of rock (sedimentary, maybe ash)
○ Area with good exposure
○ The right paleoenvironment
■ Was rock formed in desert, lake, ocean, etc.?
○ The right time period
● Age determination
○ Relative dating: the age of rocks compared to other rocks
○ Absolute dating: the age of rocks in years
● Geological time-scale provides relative and absolute ages info simultaneously
● Relative dating principles
○ Nicholas steno
1. Original horizontality
2. Lateral Continuity
3. Super position
a. Strata form by the accumulation of rock particles
i. Lower = older, higher = younger
● James Hutton
○ Deep time - earth is really really old
■Uniformitarianism: the present is the key to the past
● Physical processes observed today operated in the geological
past
● Slow processes acting over immense time have helped shaped
earth’s surface
● Modern processes help us unravel ancient events
○ Since Hutton’s time, we’ve also learned about the
importance of some fast and sudden processes.
4. Cross cutting Relationships (& erosional contacts)
● A rock unit is older than any feature that cuts or disrupts it.
○ Rock that cuts across is called a dike
●Erosional contact (unconformity): Siccar Point
○ Vertical beds of Silurian sandstone (425 ma)
○ Overlain by gently dipping, devonian red beds (345 ma)
○ Tons of missing time (80 million years)
5. Faunal Succession
● George Cuvier
● Species are always in the same sequence
○ Species evolves and goes extinct
■ Therefore only preserved in rocks of certain ages
● Fossils and Faunal Succession
○ Millions of organisms have evolved over time
Document Summary
The right type of rock (sedimentary, maybe ash) Was rock formed in desert, lake, ocean, etc. Relative dating : the age of rocks compared to other rocks. Absolute dating : the age of rocks in years. Geological time-scale provides relative and absolute ages info simultaneously. Nicholas steno: original horizontality, lateral continuity, super position, strata form by the accumulation of rock particles i. Deep time - earth is really really old. Uniformitarianism : the present is the key to the past. Physical processes observed today operated in the geological past. Slow processes acting over immense time have helped shaped earth"s surface. Modern processes help us unravel ancient events. Since hutton"s time, we"ve also learned about the importance of some fast and sudden processes. A rock unit is older than any feature that cuts or disrupts it: cross cutting relationships (& erosional contacts ) Rock that cuts across is called a dike. Vertical beds of silurian sandstone (425 ma)
