1. Geologic Time When time rocks…. Get It?!!

2. Geologic Time Geologic Time: Is the study and interpretation of Earth’s past. By looking at a cross-section of land, or an outcrop, we can gain evidence about how it formed. It is like solving a puzzle

3. If It’s a Puzzle, We Need…. The puzzle pieces. Two types of ages: Relative Dating: when we compare the age of a rock or event to another rock or event in a geologic sequence (no numerical age, just a round about age) Absolute Dating: the actual, numerical age, of a rock or event. We are going to begin with relative aging.

4. 1.) The Principle of Uniformiatrianism WHAT!!!!!! Uniform: The same -trianism: Processes “the present is the key to the past” All of the geologic processes that shape the Earth today are the same ones that shaped the Earth in the past. This rule always starts us out.

5. Geologic Processes Early Earth: Volcanism Pangea: Tectonic Plate Movement Formation of Landscapes: Weathering and Erosion All of these were found in rock records from the past and the present. So we can assume it will occur in the future as well.

6. 2.) The Principle of Original Horizontality Sediments are deposited in horizontal layers that are parallel to the surface on which they were deposited.

7. If layers are not completely horizontal, an unconformity (erosion)must have come after the layer was created. This is usually our second piece of evidence in most landscapes.

8. 3.) The Principle of Superposition In a series of undisturbed layers, the oldest layer is on the bottom and each layer on top of that gets progressively younger.

10. This does not apply in cases where layers have been overturned or where older rocks have been forced over younger layers along a fault.

11. Folding and Faulting These mess up the principle of superposition.

12. Index Fossils Index Fossils: Fossils that can help us determine the relative age of a layer. They are distributed over a large geographic area but for a short amount of time. (horizontally not vertically) Wide Spread Geographic Area Time

15. Looking At Events 4.) Igneous Intrusion and Extrusions: Igneous INtrusion: when molten magma forces its way through other layers is called an intrusion. Contact Metamorphism shows this. Igneous EXTrusion: When lava solidifies at Earth’s surface, it forms a mass of igneous rock called an extrusion.

16. Rules 1.PU 2.POOH 3.PSP 4.U/E 5.F/F 6.Ig (int/ext) 7.CCR EVENTS

18. Radioactive Decay Radioactive Decay: Occurs when unstable atoms break down (decay) into radioactive elements (decay product). Atoms with the same number of protons but a different number of neutrons are called isotopes. C 6 protons 6 neutrons 12 8 neutrons 6 protons C 14 Radioactive isotope Stable atom

19. Half-Life Half-life is the amount of time it takes for the original product to disintegrate (break down) by half into the decay product CARBON-14 is used for fossils b/c of its short half- life

20. Number of Half- Life YearsOrig. %Decay %Orig. Grams Left Pie Chart