1. Fossils and Geologic Time
IT IS TIME TO ROCK!!!!!

2. How Old is the Earth?
Before 18th Century – Earth = 6000 yo Based on Biblical Genealogies
During 18th Century – Focus turned to Science
20th century Pierre and Marie Curie discovered radioactive decay – Lead to radioactive dating
Using radioactive Decay – Earth = 4.6 Billion Years

3. Earth formed about 4.6 billion years ago.
Chapter 14
The History of Life
14.1 Fossil Evidence of Change
Land Environments
Earth formed about 4.6 billion years ago.
Gravity pulled the densest elements to the center of the planet.
After about 500 million years, a solid crust formed on the surface.

4. 14.1 Fossil Evidence of Change
Chapter 14
The History of Life
14.1 Fossil Evidence of Change
Atmosphere
The gases that likely made up the atmosphere are those that were expelled by volcanoes.
Water vapor (H2O)
Carbon dioxide (CO2)
Sulfur dioxide (SO2)
Carbon monoxide (CO)
Hydrogen sulfide (H2S)
Hydrogen cyanide (HCN)
Nitrogen (N2)
Hydrogen (H2)

5. A fossil is any preserved evidence of an organism.
Chapter 14
The History of Life
14.1 Fossil Evidence of Change
Clues in Rocks
A fossil is any preserved evidence of an organism.
Most organisms decompose before they have a chance to become fossilized.

6. The History of Life

9. Nearly all fossils are formed in sedimentary rock.
Chapter 14
The History of Life
14.1 Fossil Evidence of Change
Fossil Formation
Nearly all fossils are formed in sedimentary rock.
The sediments build up until they cover the organism’s remains.
Minerals replace the organic matter or fill the empty pore spaces of the organism.

10. Geologic Measure of Time: Relative Dating
This Type of measure was created by Hutton, Steno, and Smith:
Main idea is that the Earth, like an onion or ogre (apparently), is made of Layers.
The further down the layer, the older it is.
This is better known as Superposition.

11. Superposition

12. Absolute dating
Absolute dating is based upon the fact that atoms of radioactive elements decay to form stable isotopes
Important data about atoms:
Atoms are the smallest particles of elements
Atoms are composed Protons, Neutrons, and electrons
Number of Protons = Atomic number

14. Absolute dating
Not all atoms of the same element have the same number of neutrons in their nuclei; these variable forms are called isotopes

15. Radioactive Decay
Radioactive Isotopes = Atoms that are unstable due to having too many neutrons -> Over time they lose Neutrons and Protons (decaying).

16. Radioactive Decay
Half-Life: Amount of time required for 50% of original radioactive Material (Parent) to decay/convert into the new, lower energy form (daughter). -> Used to calculate ages

18. Absolute Dating
Radioactive elements useful in absolute dating include:
Uranium 235 (Lead 207) Half-life = 713 Million Years
Potassium 40 (Argon 40) Half-life = 1.3 Billion Years
Uranium 238 (Lead 206) Half-life = 4.5 Billion Years
Rubidium 87 (Strontium 87) Half-life = 47 Billion Years
Carbon-14 (Carbon 12) Half-life = 5700 Years

19. Absolute dating
Radioactive Dating only useful on materials containing radioactive atoms.

20. The Geologic Time Scale
Geologic Time Scale: graphical representation of the history of the Earth, divided into units based on geologic events
Originally was based on Relative Dating only. Radioactive dating made the one we use today possible.

22. Major Extinctions Cretaceous–Paleogene extinction event 65 mya
Death of the Dinos.
Caused: Combo of Climate Change, Asteroid Impact, Volcanic Activity
Triassic–Jurassic extinction event
199 mya to 214 mya
50+ % life wiped out. Allowing Dinos to dominate Caused: Combo of Climate Change, Asteroid Impact, Volcanic Activity
Permian–Triassic extinction event
251 mya
96% of life wiped out. Cause: Massive volcanic eruption
Late Devonian extinction
364 mya
~75% of life wiped out. Cause unknown.
Ordovician–Silurian extinction events
439 mya
86% of life wiped out Cause: Ice Age, Lowering Sea Levels.