1. Earth’s history

2. Geologic time
Lesson 1

3. Evidence that earth has changed – Rock layers
The principle of superposition states that in rock layers that have not been folded or deformed, the oldest rock layers are on the bottom
This gives the relative age of the rocks

4. Rock layers
The largest sediment particles are usually deposited near the bottom of a rock layer

5. fossils
The preserved remains or evidence of past living organisms are called fossils

7. radioactivity
Radioactive decay is the process by which an element naturally changes into another
The original element is called the parent element and the new element that forms is called the daughter element.

10. If you start with 1,000 atoms, how many atoms would remain after 2 half-lives?
After one half-life = 500 atoms
After two half-lives = 250 atoms

12. Geologic time scale
The geologic time scale is a visual record of Earth’s history, with the individual units based on changes in the rocks and fossils.
Geologists divide Earth’s history into eons, eras, periods, and epochs.

13. Imagine…

14. Slow vs. fast changes Fast changes Erosion Weathering Deposition
Slow changes
Fast changes
Erosion
Weathering
Deposition
Landslides
Volcanic eruptions
Earthquakes

15. Ancient earth
Lesson 2

16. Gravity and the solar system
The solar system started as a nebula, a cloud of gas, ice, and dust.
Gravity pulled the particles together into a flattened disk shape that began to rotate.

17. Spherical earth Earth became larger as more particles came together
Collisions produce thermal energy, so the colliding particles warmed the new planet

18. https://ed.ted.com/on/yRWszobe

19. Spherical Earth
Gravity pulled the hot rocks into the shape of a sphere
Asteroids continued to crash into the surface, making Earth even hotter

20. Hadean eon
It was very hot during the Hadean eon due to collisions with asteroids and large amounts of radioactive decay

21. Hadean eon During the Hadean Eon there was: Formation of Earth’s core
Cooling
Seas of molten rock
Small islands of solid rock

22. Early atmosphere
During the Hadean eon, there was an atmosphere of water vapor, carbon dioxide, and poisonous gases (no oxygen) due to volcanic activity

23. The Archean eon During the Archean eon, the temperature dropped
Earth had its first solid surface
The Archean continents were called protocontinents

24. The Archean eon
The temperature drop led to the condensation of water vapor
The rain was acidic and dissolved salts forming salty oceans

25. The Archean eon
The earliest evidence of life is present in rocks that formed in the warm Archean oceans

26. The Proterozoic eon
The Earth continued to cool during the Proterozoic eon
There was an increase in oxygen
The Snowball Earth hypothesis suggest the whole Earth was covered with ice

27. The Proterozoic eon
The first multicellular organisms evolved in the oceans

28. The Cambrian explosion
Lesson 3

29. The Cambrian explosion
The change in life on Earth during the beginning of the Phanerozoic eon is known as the Cambrian Explosion

30. The Cambrian explosion (continued)
Scientists hypothesize that continents were breaking apart, temperatures were increasing, and sea levels were rising
Some organisms became adapted to the new environment

32. The impact of asteroids
Scientists hypothesize that an asteroid impact might have contributed to the mass extinction that occurred at the end of the Cretaceous period
Many animals, including dinosaurs, became extinct

34. Earth’s changing surface
Volcanic activity has decreased, but continues today forming oceanic crust, building mountains, and powering the rock cycle
Mountains continue to build as plates move