Transcript Inside Restless Earth 3

Sci. 3-2 Relative
Dating: Which Came
First?
Pages 59- 63
A. Relative Dating- determining whether
an object or event is older or younger than
other objects or events.
B. The Principle of Superposition- states
that younger rocks lie above older rocks as
long as the rocks have not been disturbed.
C. Geologic Column- an ideal sequence of
rock layers that contains all the known
fossils and rock formations on Earth
arranged from oldest to youngest.
D. Disturbed Rock Layers
1) fault- a break in the Earth’s crust
along which blocks of crust slide relative to
one another.
2) Intrusion- molten rock that
squeezed into existing rock and hardened
3) Folding – when rocks bend and
buckle from Earth’s internal forces
4) tilting- when rock layers slant
E. Unconformities- when a layer or several
layers of rocks are missing from a rock
layer sequence, a gap
1)Means missing time, time not
recorded by rock layers
F. Types of Unconformities
1) Disconformity- exists where part of a
sequence of parallel rocks layers is
missing ( Hard to see, most common)
2) nonconformity- exists where
sedimentary rock layers lie on top of an
eroded surface of nonlayered igneous or
metamorphic rock.
3) angular unconformity- exists between
horizontal rock layers and rock layers that are
tilted or folded. The tilted or folded layers were
eroded before the horizontal layers formed
above them.