L7 - How Old Is the Earth? Flashcards Preview

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Flashcards in L7 - How Old Is the Earth? Deck (17):
1

Who was the first person to try and date the Earth, what were his methods and what number did he come up with?

- James Ussher, 1654
- BibHule
- 4004BC

2

Who was the second person to try and date the Earth, what were his methods and what number did he come up with?

- Nicolaus Steno, 1638-86
- Shark teeth
- None in particular but evidence the world had changed

3

Who was the third person to try and date the Earth, what were his methods and what number did he come up with?

- Compte de Buffon, 1778
- Cooling ball of metal
- 75,000yrs

4

Who was the fourth person to try and date the Earth, what were his methods and what number did he come up with?

- James Hutton
- Uniformitarianism
- No definitive age, just very very old

5

What are the four principles of uniformitarianism?

Superposition
Original Horizontality
Cross-cutting relationships
Unconformities

6

Give an example of uniformitarianism

Sand ripples on a beach today is observable in sandstone from 1000s of years ago

7

Why might uniformitarianism not hold true?

Species and climates can change radicallly, with no analogues in modern day

8

How is relative dating different from absolute dating of rock layers?

You can say that rock X is older than rock Y without actually knowing the age of either through principles of uniformitarianism.

9

Explain superposition

Newer layers layered on top of older ones

10

Explain original horizontality

Layers are laid down horizontally
Sediment rarely accumulates on a slope

11

Explain cross-cutting relationships

Younger features will truncate older features

12

Explain unconformities

Unconformities (where two layers of rock are radically different) tend to represent huge gulfs in time. With the rocks above the unconformity beinng significantly older than those below.

13

Who was the fifth person to try and date the Earth and what number did he come up with?

John Joly, late 19th century
90 million years

14

Who was the sixth person to try and date the Earth and what number did he come up with?

Lord Kelvin, late 19th century
20-30 million years

15

How did we uncover the real age of the Earth

Radiometric dating

16

How does radiometric dating work?

By measuring amount of 'daughter atoms' in a mineral and thus, using pre-existing knowledge of the half-life of the element, 'counting-back' to find the age of the material.

17

State the name and origin of the world oldest rock

Acasta Gneiss, Canada