Transcript Interpreting Earth’s History - Red Hook Central School Dst

Interpreting Earth’s History
How can rocks be correlated?
And
Geologic Time Scale
Index Fossils
 Index fossils are:
A. commonly found
widely distributed
C. limited in time span.
 They help in dating other fossils found in
the same sedimentary layer.
 Humans will one day make excellent index
fossils
B.
Correlation- DO NOT WRITE
 Correlation- or CO-RELATION (two or more
things related) is a critical tool in the
reconstruction of Earth’s history.
 Geologists try to match similar rock strata in
different locations to see if they formed at the
same time or under similar conditions
Who’s got the TIME?- DO NOT
WRITE! In notes from yesterday
 RELATIVE: order/sequence known,
but not the actual date of occurrence.
 ABSOLUTE: actual date known. If 2
dates are known, then the RATE OF
CHANGE can be known- such as
Mountain Building.
First Things First…or…“How’d that get
there?” (DO NOT WRITE)
 In the 17th C., Nicolas Steno made an
important observation:
 "Sediments are usually deposited in
horizontal layers." This was called:
“ORIGINAL HORIZONTALITY”
REVIEW: DO NOT WRITE
 SUPERPOSITION: sedimentary sequence will be
OLDEST on BOTTOM (if undisturbed).
 CROSS-CUTTING: igneous rock is younger than
rocks it has intruded (cut across).
 INCLUDED FRAGMENTS: pieces of rock
found IN another rock must be OLDER (formed
first).
Geologic Time
(WRITE THIS)
 Using our best data, the Earth is about 4.6
billion years old
 That’s 4,600,000,000 years!
How do we know the Earth’s age, and
which rocks are older?
 No one was around to tell us the age.
 Many experiments using radiation
found in rocks tell us.
 The “Law of Superposition” can also
help tell which rocks are older than
other rocks.
DIVIDING UP THE EARTH’S AGE
 ESRT page 8 (ESRT is behind page 264 in RRB)
 Just as we have hours and minutes, the Earth’s
time has also been broken up into units called
ERAS.
 The ERAS do not have a set amount of time like
the hour. Some ERAS, then, are longer than
others.
 ERAS are broken down farther into PERIODS.
THE CENOZOIC ERA
 We are currently living in the Cenozoic Era.
 The Cenozoic Era has lasted for about 63 million
years.
 There are only two periods in the Cenozoic Era:
1. The Tertiary Period
2. The Quaternary Period - the current period
THE MESOZOIC ERA
 Known as the “Age of the
Dinosaur”
 Started about 265 million years ago.
 Contained three periods:
1. The Triassic
2. The Jurassic
3. The Cretaceous
THE PALEOZOIC ERA
 Known as the “Age of Fish”
 Started about 570 million years ago.
 Lasted about 340 million years
 Toward the end of this era coal began to form.
The PRECAMBRIAN
 Known as “Age of Bacteria”
 During much of this time there was no life on earth.
 The earth was still hot
 The atmosphere was not like it is now.
 The Precambrian Era lasted for the first 4 billion years of
Earth’s history.
EARTH’S GEOLOGIC ERAS- DO NOT
WRITE
 PRECAMBRIAN
-rocks form, atmosphere
 PALEOZOIC
-fish, amphibian,coal forms,
Appalachian Mt. peak
 MESOZOIC
-dinosaur, birds, flowers
 CENOZOIC
-horses, humans, last ice age