Warm-Up

Warm-up 10/20Describe what you think Earth was like just after it formed.

Early History of EarthFormation4.6 billion years ago (bya)Nebular TheoryMoltenVolcanoesCollisions

AtmosphereCO2Biological influencePink in color

Gradually cooled 3.9 bya oceans form Water from comets, planet Condensation led to rain Runoff brings mineralshttp://www.globalchange.umich.edu/globalchange1/current/lectures/Perry_Samson_lectures/evolution_atm/2Warm-up 10/21-22Approximately how old is Earth?

How do you think scientists determined that age?

Relative DatingDetermining the relative order of past events.

Estimate of age based on position

Ryan Gosling was born after Matt McConaughey.

Three rules

What order did the baker put down these layers of the cake?Purple!Blue!YellowRed!Dark Pink!Light Pink!White!

#1: Law of Superposition (LOS)Bottom layer =Top layer =Placed lastPlaced first*When rocks are horizontal!6What happens if rock layers are not horizontal?

Layers deposited horizontally

Rock is folded after cooling - Caused by pressure

Bottom is still oldest.

Top is still youngest.

OLDESTYOUNGEST2. Principle of Horizontality

Practice: Hold up the numberWhich is the oldest? Which layer is the youngest?

What happens if the rock layers are faulted?

1. A fault is younger than any rock layer it cuts through. OLDEST2ND OLDEST3RD OLDESTYOUNGEST3. Principle of Cross-Cutting Relationships2. An intrusion is younger than the rock layers it pushes through.

OLDEST2ND OLDESTINTRUSION = YOUNGESTIntrusion magma forces its way through the rock layers.Practice!

Practice!

Tell the rocks story