Beginning Practice for Relative Dating

Name: __________________________________________ Date: ____________________________ Core: ___________ Relative Dating of Rock Layers Principles for Relative Dating: 1) Law of Original Horizontality – Sedimentary rock layers are formed in horizontal layers due to the force of gravity. If the layers are all still connected, but no longer horizontal (appear diagonal) they have undergone tilting. 2) Law of Superposition – The oldest layers are generally found at the bottom and the younger layers are generally found at the top. 3) Extrusion – A lava flow that hardens on the surface in a flat horizontal layer. 4) Intrusion – A plume of magma from the Earth's mantle will rise up and cut
through previously formed layers before hardening into an igneous rock.
Intrusions are often vertical or diagonal, irregular in shape, and are younger than
every rock layer it cuts through.
5) Fault -‐ A break and shift in the Earth's crust and rock layers. Layers appear cut
in half. Faults are always younger than the rock layers they cut through/shift.
Practice Problem #1: Order of Occurrences: 1st (Oldest Event): Second: Third: Fourth: Fifth (Youngest Event): Practice Problems #2: Order of Occurrences: 1st (Oldest Event): 2nd: 3rd: 4th: 5th: 6th: 7th: 8th: 9th: 10th (Youngest Event):

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