Relative dating is determining whether an object or event is older or younger than other objects or events. Think Younger is "super" over older. In a rock-layer sequence that hasn't been disturbed, are older layers found on top of younger layers?
What rule do you use to answer this question? No, younger layers are on top and the rule you use is superposition. What is a Geologic column? Geologist use this interpret rock sequences. Demonstrate an understanding of the geologic column?
You can have three different rock sequences from three different locations. Some rock layers appear in more than one sequence. Geologist construct the geologic column by piecing together different rock sequences from all over the world. Draw diagram on pg Like Lord of the rings. One Geologic column rules them all. It tells you where other rock sequences around the world would fall.
Ie how old they are. What is younger rock layers or features that cut threw them? Consider a fault that cuts through all the layers of a rock-layer sequence is the fault older or younger than the layers?
Geologist assume that the way sediment is deposited to form rock layers - in horizontal layers - has not changed over time so if the rock layers are not horizontal something disturbed them after they were formed. Therefore, The rock layers have to be older otherwise the features would have nothing to cut threw. G List and Describe 5 events or features that can disturbed rock-layer sequences?
Fault is a break in the earths crust along which blocks of the crust slide relative to one another. Intrusion is molten rock that squeezes into existing rock and cools.
Missing time that was not recorded in the layers of the rock. Folding when rock layers bend and buckle from Eaths internal forces. What are examples of features that cut across rock layers? What are examples of two events that cut across rock layers? What creates a gap in columns? Unconformity What two things can cause unconformity? Explain Non-Deposition - sediment supply is cut off and then resumed.
Disconformity - part of a sequence of parallel rock layers is missing. Angular unconformities - exists between horizontal rock layers and rock layers that are tilted or folded and eroded before horizontal layers formed above them. Unlike other types of unconformities, disconformites, are hard to recognize because all the layers are horizontal.
How does a geoplogist know when he or she is looking at a disconformity? Explain how physical features are used to determine relative ages?