relative dating

Question 1

What is the difference between relative dating and absolute dating?

Answer 1

Relative: when events occurred relative to one another. “which one came first”
Absolute: when events actually happened. “How old is it?”

Question 2

What different diagnostic methods are used to assess relative and absolute
geologic age?

Answer 2

• principles of superposition, original horizontiality, corss cutting relationships, inclusions, funal successions, and correlation

Question 3

Principle of Superposition

Answer 3

• Nicholas Steno, 1669
• in any undisturbed sedimentary rock, the oldest layer will always be at the bottom, successively
  younger layers on top

Question 4

What are unconformities?

Answer 4

• a gap in the geological record; most often an erosion surface

Question 5

Principle of Original Horizontality

Answer 5

• Nicholas Steno
• beds of sediment laid down in water form horizontal layers on top
• original rocks started as horizontal; an event occurred which caused folding

Question 6

Principle of of Cross-Cutting Relationships

Answer 6

• Steno (1669), Hutton (1795), Lyell (1830)
• a geological feature that cuts across or perpendicular another body of rock much be younger than the rock mass penetrated

Question 7

Principle of Lateral Continuity

Answer 7

• Steno
• layers of rock care continuous until they encounter other solid bodies that block their deposition or until they are acted upon by agents that appear after deposition took place

Question 8

Principle of Inclusions

Answer 8

• Lyell, 1830
• fragments included in the host rock are older than the host rock

Question 9

Principle of Faunal successions

Answer 9

• Smith, 1800
• fossil species succeed one another in a recognizable order
• index fossils relate to specific time period

Question 10

Correlation

Answer 10

• determining time equivalency of rock units
• similarity in lithology and/or fossils
• 3 types: disconformity, angular unconformity, and nonconformaity

Question 11

Disconformity

Answer 11

• layers above and below the unconformity are parallel to eachother

Question 12

Angular Unconformity

Answer 12

• younger beds overlie tilted or folded beds

Question 13

nonconformity

Answer 13

• younger beds overlie much older metamorphic or plutonic rocks