Transcript Relative Dating Notes

James Hutton
Uniformitarianism:
the processes that
act on the Earth’s
surface today are
the same as the
processes that
have acted on the
Earth’s surface in
the past
“The present is the key to the past”
age of anything
compared to the
age of something
else
•doesn’t indicate actual
date of occurrence
law of superposition: in
undisturbed rock, the older
rocks will be at the bottom
and the youngest rocks will
be at the top
law of cross-cutting
relationships:an igneous rock
cutting through another rock
is younger than the rock it
has cut-cross
law of included fragments:
pieces of one rock found in
another rock must be older
than the rock in which they
are found
unconformity:
break in
the
geologic
rock
record
Contorted rock, hard to determine relative age (Copiapo, Chile)
•nonconformity: when
stratified rock rests upon
unstratified rock
Noncomformity
1. Granite formed
2. Granite exposed by erosion
3. Beds 1-3 deposited
•angular unconformity:
boundary between horizontal
and tilted layers of rock
Angular Unconformity
1. Beds 1-6 deposited
2. Beds 1-6 tilted
3. Erosion
4. Beds 9,10 deposited
•disconformity:boundary
between layers of rock that
have not been deposited
continuously
Disconformity
1. Beds 1,2 deposited
2. Erosion
3. Beds 5, 6, 7 deposited