# Use answer key to make correction to p. 2 in binder

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Use answer key to make correction to p. 2 in binder
DO NOW (Period 2 & 7 only) Use answer key to make correction to p. 2 in binder DO NOW QUESTION What kind of unconformity is shown below? Explain. Choices: Disconformity Nonconformity Angular

Relative Dating: Which came first?
Chapter 6.2

What is relative dating?
Used to determine which events happened in Earth’s past Used to determine if an object/event is older or younger than other objects/events

What is relative dating?

Put in order from oldest to youngest… A B C D
OLDEST C  A  B  D YOUNGEST

What is the principle of superposition?
Younger rocks lie above older rocks in undisturbed sequences Sequence = order

Purple (oldest – laid down first) Blue Green Yellow Orange Red (youngest – laid down last)

Grand Canyon – Arizona, USA

How do geologists Use the geologic column?
Undisturbed sequence of rock layers containing fossils and rock formations Arranged from oldest to youngest Geologists use to interpret information in rock sequences Created by combining data from all known rock sequences in an area

How can a rock layer can be disturbed?
Fault break in Earth’s crust where plates slide past one another Intrusion molten rock inside Earth pushes into rock and cools Folding rock layers bend and buckle from forces in Earth Tilting forces in Earth slant rock layers

FAULT break in Earth’s crust where plates slide past one another

Intrusion molten rock inside Earth pushes into rock and cools

Folding rock layers bend and buckle from forces in Earth

Tilting forces in Earth slant rock layers

What is an unconformity?
Surface that represents a missing part of the geologic column (missing rock layer) Caused by nondeposition (sediment is no longer being despoited) or erosion (transport of sediment elsewhere)

How does a disconformity occur?
Rock layers are uplifted and eroded away In the future, sediment is deposited on top of the old erosion surface Most common type of unconformity Part of a horizontal sedimentary rock sequence is missing

How does a nonconformity occur?
Intrusive igneous or metamorphic rock is uplifted and eroded away In the future, sediment is deposited on top of this igneous or metamorphic rock Horizontal sedimentary rock layers on top of eroded surface of older igneous or metamorphic rock

How does a angular nonconformity occur?
Forces in Earth tilt of fold layers of rock Tilted or folded rock is uplifted and eroded away In the future, horizontal layers of sediment is deposited Occurs between horizontal layers of sedimentary rock and tilted or folded layers of sedimentary rock