Transcript Science Olympiad Fossils Division B

Science Olympiad
Fossils
Division B
2015
3- Geological Time &
Index Fossils
Geological Time
•The ages of geological Time
Geologic time scale
http://www.geosociety.org/science/timescale/timescl.pdf
Geological Time
The basic unit of geologic time is 1 ,000,000 (one million) years. A million is an
incredible number. To better understand how long one million years is, we
can convert it to some more familiar unit of measure. If we let one inch equal
one thousand years, then one million years would equal 83.3 feet. One
hundred years (longer than the average life span) would be represented by
just one tenth (1/10 or 0.1) of an inch. If one goes back to the beginning of
the Cambrian Period, some 570,000,000 years ago - one would need almost
9 miles to represent this part of the Earth history. To map out all of geologic
time, one would need more than 72 miles.
The lowest layers formed first and are the oldest. As you progress up a column
of rocks you progress through younger and younger layers. Early geologists
used fossils as markers to correlate and thereby determine the relative ages
of rocks. This led to the ability to construct a geologic column made up of
rocks of different ages from different locations.
•
Written, compiled and illustrated by Midwest Mineralogical and Lapidary Society of Dearborn, Michigan
Geological Time
The geologic history of the Earth is broken up into hierarchical chunks of
time. From largest to smallest, this hierarchy includes eons, eras,
periods, epochs, and ages.
From Wed site: http://www.ucmp.berkeley.edu/education/explorations/tours/geotime/gtpage6.html
These time intervals are not equal in length like the hours in a day. Instead
the time intervals are variable in length. This is because geologic time is
divided using significant events in the history of the Earth.
Examples of Boundary "Events“
For example, the boundary between the Permian and Triassic is marked by
a global extinction in which a large percentage of Earth's plant and
animal species were eliminated. Another example is the boundary
between the Precambrian and the Paleozoic which is marked by the first
appearance of animals with hard parts.
From Web site: http://geology.com/time.htm
Geological Time
Eons - Are the largest intervals of geologic time and are hundreds of millions of years
in duration. In the time scale above you can see the Phanerozoic Eon is the most
recent eon and began more than 500 million years ago.
Eras - Eons are divided into smaller time intervals known as eras. In the time scale
above you can see that the Phanerozoic is divided into three eras: Cenozoic,
Mesozoic and Paleozoic. Very significant events in Earth's history are used to
determine the boundaries of the eras.
Periods - Eras are subdivided into periods. The events that bound the periods are
wide-spread in their extent but are not as significant as those which bound the
eras. In the time scale above you can see that the Paleozoic is subdivided into the
Permian, Pennsylvanian, Mississippian, Devonian, Silurian, Ordovician and
Cambrian periods.
Epochs - Finer subdivisions of time are possible and the periods of the Cenozoic are
frequently subdivided into epochs. Subdivision of periods into epochs can be done
only for the most recent portion of the geologic time scale. This is because older
rocks have been buried deeply, intensely deformed and severely modified by longterm earth processes. As a result, the history contained within these rocks can not
be as clearly interpreted.
Ages – is the smallest subdivision
From Web site: http://geology.com/time.htm
Geological Time
• The Phanerozoic Eon represents the time during which the majority of
macroscopic organisms — algae, fungi, plants and animals — lived. When
first proposed as a division of geologic time, the beginning of the
Phanerozoic (542.0 million years ago)* was thought to coincide with the
beginning of life. In reality, this eon coincides with the appearance of
animals that evolved external skeletons, like shells, and the somewhat later
animals that formed internal skeletons, such as the bony elements of
vertebrates. The time before the Phanerozoic is usually referred to as the
Precambrian and is usually divided into the three eons.
•
From Wed site: http://www.ucmp.berkeley.edu/education/explorations/tours/geotime/gtpage6.html
Geological Time
• The Phanerozoic is subdivided into three major divisions: the Cenozoic,
Mesozoic, and Paleozoic Eras. The "-zoic" suffix comes from the root "zoo,"
which means animal.. "Cen-" means recent, "Meso-" means middle, and
"Paleo-" means ancient. These divisions reflect major changes in the
composition of ancient faunas, each era being recognized by its domination
by a particular group of animals. The Cenozoic has sometimes been called
the "Age of Mammals," the Mesozoic the "Age of Dinosaurs," and the
Paleozoic the "Age of Fishes." But this is an overly simplified view, which
has some value for the newcomer but can be a bit misleading. For instance,
other groups of animals lived during the Mesozoic. In addition to the
dinosaurs, animals such as mammals, turtles, crocodiles, frogs, and
countless varieties of insects also lived on land. Additionally, there were
many kinds of plants living in the past that no longer live today. Ancient
floras went through great changes too, and not always at the same times
that the animal groups changed.
•
From Wed site: http://www.ucmp.berkeley.edu/education/explorations/tours/geotime/gtpage6.html
Ages of Geological Time
Era
Cenozoic
Period or Epoch
Pleistocene
Age
Age of Man
Pliocene
Miocene
Oligocene
Age of Mammals
Eocene
Paleocene
Mesozoic
Cretaceous
Jurassic
Age of Reptiles
Triassic
Paleozoic
Permian
Carboniferous
Age of Amphibians
Devonian
Silurian
Age of Fishes
Ordovician
Cambrian
Age of Sea Life
An Example of the Law Super position
Picture from Web Site: http://www.t-rat.com/Pages/WhereToFindFossils.html
This example correlates formations throughout a large region in the southwestern part of
the United States noted for its spectacular scenery. The composite section can be
thought of as representing a large, although incomplete, segment of relative geologic
time. A global time scale has been derived by extending the correlations from one place
to another and reaching from one continent to another. These correlations are based in
large part on fossil evidence.
Return to Relative Time Scale
Relative Dating
• Relative dating orders events in chronological order. It tells you which
events came first, but it does not tell you the exact date of which it
occurred. There are different methods that are used for relative dating.
They are the principle of superposition, the principle of original
horizontality, the principle of cross-cutting relationships, and the principle
of inclusions.
• Principle of Superposition: If you have undisturbed layers of
sedimentary rocks, than the layers will be younger as they near the top.
The oldest layers are on the bottom and the tallest layers are on the top.
• Principle of Original Horizontality: Rocks are originally layered
horizontally. If you have layers that are higher on one side than on the
other, it is due to the tilting of rocks caused by a geological event.
• Principle of Cross-Cutting Relationships: This principle states that a
fracture or cut in a rock caused by another rock (igneous intrusion) is
always younger than the rock it cuts.
• Principle of Inclusions: Fragments of one rock in another rock must be
older than the rock it is contained in.
From Web site: http://scioly.org/wiki/index.php/Fossil
Absolute Dating
• Absolute dating is similar to relative dating in that they both order events in
chronological order. However, unlike relative dating, absolute dating can
determine the ages of rocks. There are several methods that are used in
absolute dating, including radiometric dating, half-life, and carbon dating.
• Half-life: The half-life of an isotope is how much time it takes for half the
atoms in that isotope to decay. After that many years, half the atoms in the
isotope will decay. After that many years again, half of that half (one
quarter of the whole or two half-lives) will decay. After that many years
again, half of the half of that half (one eighth of the whole or three halflives) will decay. It will go on until the isotope decays to its daughter
product.
• Major radioactive isotopes and their half-life:
- Carbon 14 5730 years
- Potassium 40 1.25 Ga years
- Uranium 235 703.8 Ma
- Uranium 238 4.468 Ga
- Thorium 232 14.05 Ga
- Rubidium 87 48.8 Ga
- Samarium 147 106 Ga
Ma = Million Years
Ga = Billion Years
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From Web site: http://scioly.org/wiki/index.php/Fossil
NEW GEOLOGICAL PERIOD
ADDED
NEW GEOLOGICAL PERIOD ADDED
On May 13, 2004, the International Union of Geological Sciences (IUGS) announced the
first new geological period declared in 120 years—the Ediacaran Period. The IUGS is
an international non-governmental organization devoted to international cooperation in
the field of geology. One of its daughter groups, the International Commission on
Stratigraphy, is the generally accepted authority on the names and starting/ending dates
of the various subdivision of the geological time scale. The Ediacaran Period takes its
name from the Ediacara Hills, located in the Flinders Ranges of South Australia, the
location of the type site or Global Boundary Stratification and Selection Point (GSSP).
The Ediacaran is the last geological period of the Neoproterozoic Era, just preceding the
Cambrian Period of the Paleozoic Era. Its assigned time range is 635 to 542 million
years ago.
Since animals with hard shells (exoskeletons) did not appear until the Cambrian Period,
the fossil record for the new period is sparse. However, the Ediacaran biota include the
oldest definite multicellular organisms with tissues, the most common types resembling
segmented worms, fronds, disks, or immobile bags. They bear little resemblance to
modern lifeforms, and their relationship even with the later lifeforms of the Cambrian
explosion is difficult to interpret. More than 100 genera have been described, and well
known forms include Arkarua, Charnia, Dickinsonia, Ediacaria, Marywadea, Onega,
Pteridinium, and Yorgia.
NEW GEOLOGICAL PERIOD ADDED
Although the Ediacaran Period does contain soft bodied fossils, it is unusual
in comparison to later periods because its beginning is not defined by a
change in the fossil record. Rather, the beginning is defined at the base of a
chemically distinctive carbonate (a salt or ester of carbonic acid) layer,
referred to as a "cap carbonate," because it caps glacial deposits and
indicates a sudden climatic change at the end of an ice age. This bed is
characterized by an unusual depletion of C-13, and is considered by many
scientists to be of global extent.
Geological Time
Review file on CD: Fossils2002.pps
Questions ?
Next Week’s Topics?
• Practice Tests/ Game
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4.
Flash Cards Instructions
Divide the work between team members
Check each others work
Work on the fossils assign to your team
Use the sample flash cards posted to the schools Science Olympiad web
site under the Fossil event. Sample Files are:
1. FlashCardsFusulinidsNummulites.ppt
2. FlashCardsHemichordataMucrospirifer.pptx
5. Save your flash card files using this name:
1. FlashCardsName of FossileName of Fossil
Example is: FlashCardsFusulinidsNummulites.ppt
For Fossil pictures start with these 3 files loaded on the school Science
Olympiad web site
2009-Fossil-Poster.pdf
2009-Fossil-Notes-B.pdf
2009-Fossil-Notes-B2.pdf
Another good source is:
Web Site: http://scioly.org/wiki/index.php/Fossil_List