2. F SSILS
WHAT ARE FOSSILS?
the remains or trace of a oncethe remains or trace of a once
living thing, usually preserved inliving thing, usually preserved in
sedimentary rocksedimentary rock
8. F SSILS
TYPES OF FOSSILS
IMPRINTS
Occur when leaves andOccur when leaves and
feathers leave anfeathers leave an
impression in mud thatimpression in mud that
later hardens into rock.later hardens into rock.
9. F SSILS
TYPES OF FOSSILS
ORGANISMS GET TRAPPED
IN HARDENING TREE SAP
AND ARE PRESERVED AS
FOSSILS
AMBER
10. F SSILS
TYPES OF FOSSILS
ICE
SOME ORGANISMS
MAY BE PRESERVED AS
FOSSILS IN ICE
11. F SSILS
TYPES OF FOSSILS
TAR
ANIMALS GET
TRAPPED IN
TAR PITS AND
THEIR REMAINS
GET PRESERVED-
LA BREA TAR
PITS IN
CALIFORNIA
12. F SSILS
TYPES OF FOSSILS
PETRIFIED
WOOD
PETRIFICATION OCCURS
WHEN MINERALS
DISSOLVED IN GROUND
WATER GRADUALLY
REPLACE THE ORIGINAL
TISSUES OF PLANTS AND
ANIMALS
13. F SSILS
WHAT DO FOSSILS TELL US?
APPEARANCE
AND ACTIVITIES
OF PAST LIFE
FOSSIL TEETH GIVE
US CLUES AS TO
WHAT THE ANIMAL
ATE
14. F SSILS
WHAT DO FOSSILS TELL US?
SPECIES HAS
EVOLVED OR
CHANGED
15. F SSILS
WHAT DO FOSSILS TELL US?
EARTH’S PAST
CLIMATES
NYS
458 MILLION YEARS AGO 250 MILLION YEARS AGO
FOSSIL CORAL = WARM CLIMATE
16. GE LOGIC TIME
The geologic time
scale is based on the
FOSSIL RECORD
LARGE
TIME
UNITS
SMALL
TIME
UNITS
EON
ERA
PERIOD
EPOCH
17. GE LOGIC TIME
Geologic History of
NYS- ESRT p. 8 & 9
Precambrian Eon
Archean
Proterozoic
Phanerozoic Eon
18. GE LOGIC TIME
Geologic History of
NYS- ESRT p. 8 & 9
Precambrian Eon
Archean
Proterozoic
Phanerozoic Eon
Cenozoic
Era
Mesozoic Paleozoic
21. GE LOGIC TIMEGE LOGIC TIME
Why are the sections of
geologic time separated
this way?
Major
Extinctions Major Climate
Change
Appearance
Of new
life
22.
23. GE LOGIC TIME- Model of Geologic Time
Scale
Name of Era/Eon Millions of Years
Ago
Duration Percent of Earth’s
History
Cenozoic
Mesozoic
Paleozoic
Precambrian
0 to 65
65 to 251
251 to 544
544 to 4600
65 my
186 my
293 my
4056 my
1.4%
4%
6.4%
88.1%
24. RELATIVE DATING
What is relative dating?
Determining the age of
something compared to
something else
NO NUMBER IS NEEDED!!
THIS IS JUST LIKE
SAYING:
Trilobites are older
than dinosaurs
Dinosaurs are older
than mastodonts
We do this to
determine how
old rock layers are…
27. RELATIVE DATING
Rules
for
Sequencing:
IGNEOUS INTRUSION:
An igneous intrusion
is younger than the
rock layers it
penetrates
Remember igneous rocks form from
magma. An igneous intrusion is when
magma seeps up in between rock layers
and hardens to form rock.
28. RELATIVE DATING
Rules
for
Sequencing:
CONTACT METAMORPHISM:
The contact
metamorphism is
younger than the
layers it cuts through
When the magma seeps up
between rock layers it is very
hot and it bakes the rocks around it.
The surrounding rocks do not melt
but are metamorphosed.
Duh again!!!! If there
were no rock layers
there then there
wouldn’t be anything
to turn into
metamorphic rock.
31. Relative Dating Instructions
Relative Time:
Ages of events are placed in order of
occurrence.
No exact date is identified.
Ex. WWI and WWII
"I am the second child in my family."
32. Law of Uniformitarianism
• "The present is the key to the past."
• or what we see now has almost certainly
happened before and therefore can be
used for interpreting the past.
33. Original Horizontality- Rocks are usually deposited
flat and level.
• You would say
– “Deposition of”
sandstone, limestone,
shale, etc.
– This applies to
sedimentary rocks
ONLY
34. The law of cross-cutting relationships—an
igneous rock is younger than the rocks that
it has intruded into. This also applies to
faults.
You would say— “Igneous intrusion” or
faulting/folding.
4. Faulting
3. Deposition of Shale
2. Deposition of Sandstone
1. Deposition of Limestone
35. Sequence 1: Uplift & Erosion
• Any time folding or tilting occurs
• UPLIFT will occur
• If there is uplift – EROSION will
occur
36. Unconformity
• A “gap” in the rock
record where erosion
or non-deposition
occurred.
• You must include this
as a separate step in
the sequence of
events.
37. •Layers are formed according to superposition.
Here’s How It Works!Here’s How It Works!
41. Other Guidelines for figuring out a
sequence:
• Sedimentary rocks are usually formed
under water.
• Weathering and erosion usually
happen above water (on dry land).
42. Practice Sequencing
• Turn to page 7 in your notes.
• We will complete #1 together.
• Complete #2-#6 for homework, we will go
over them tomorrow.
47. Rock Correlation
• Want to know what happened in Earth history in
widely different locations?
• Rock correlation -- hooks up rocks that look alike
– The key bed – a particular strata that is very
distinctive
– Fossil correlation -- hooks up rocks that formed at the
same time and relies on the following:
• index fossils
• Rock type (color and composition)
48. Rock Correlation:
Matching up outcrops at
different locations
Volcanic Time
Markers
Index Fossils
Rock layers have:
Same color, and
composition
56. How can we figure it out?
Radio Active decay
Radioactive
(parent element):
Atom with an
unstable nucleus
that decays
57. Radioactive
(parent element):
Atom with an
unstable nucleus
that decays
Carbon 14: Carbon
Dating
Used to date organic remains
(woods, bones) no older than
50,000 years
58. Half-Life:
Time it takes for ½ of a
radioactive element
to decay into a stable
element
Is NOT affected by:
Heat Pressure
Mass
