Relative Dating 12/7/2018
Warm-Up Q).What Kind of belief does the following statement support: “Major geologic changes in the past happened at the same rate as they do today- GRADUALLY” 12/7/2018
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What does the word RELATIVE mean? 12/7/2018
Engage When you look at a rock or fossil you might think “How old is this?” (if you’re cool) Scientists have a way of using clues found in the rock layers to estimate how old a rock is. 12/7/2018
Stratigraphy Stratigraphy:The study of the rock layers and how they relate to one another. 12/7/2018
Relative Dating The relative age of a rock is its age compared to the ages of other rocks. You use this method in your daily life all the time!! 12/7/2018
Who is older? 12/7/2018
Relative Dating You don’t know the exact age of the ladies in the photos, however, you knew based on clues you have learned that the picture on the left was older. The relative age of a rock does NOT provide its absolute age The absolute age of a rock is the number of years since the rock formed. 12/7/2018
Which is older? 12/7/2018
Order the pictures from youngest to oldest 12/7/2018
Let’s see what you can do? Which Rock is the oldest? 12/7/2018
Which is older? 12/7/2018
Which is older? 12/7/2018
Which is older? 12/7/2018
Which is older? 12/7/2018
Which is older? 12/7/2018
Relative Dating Scientists use many clues to determine which rocks are older or younger in rock structures Law of Original Horizontality Law of Superposition Law of Crosscutting relationships Law of Inclusion Law of Faunal succession Index Fossils Unconformities Disturbances 12/7/2018
Law of Original Horizontality Sedimentary rock are originally deposited in horizontal layers. Forces of the Earth (uplift, faults, erosion, tectonic plates) disturb them over time. 12/7/2018
Law of Original Horizontality 12/7/2018
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Law of Superposition The Oldest rock layer is on the bottom and the youngest rock layer is on the top in an undisturbed rock sequence. 12/7/2018
Which Rock layer is the oldest? 12/7/2018
Law of cross-Cutting Relationships Any feature that cuts across a body or segment of rock is YOUNGER than the body of rock it cuts through. 12/7/2018
Law of cross-Cutting Relationships 12/7/2018
Law of cross-Cutting Relationships An intrusion is younger than the rock layer it cuts through. 12/7/2018
Law of cross-Cutting Relationships A fault is younger than the layers that it breaks. 12/7/2018
Law of Inclusion The body of rock that contains inclusions of preexisting rock is younger than the rocks that the inclusions came from. 12/7/2018
The oldest rock in this picture is rock layer ___________ The youngest rock in this pictures is rock layer ___________ 12/7/2018