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Geological Time Scale
Transcript of Geological Time Scale
What does Geological Time Scale Mean?
It's the year 2015.... How can the Earth be 4.6 BILLION YEARS OLD???
What is Your Time Scale?
Construct a timeline of the important events in your life. Be sure to include all of the events listed below and any other events you feel are important. Your timeline should be constructed TWO ways:
Numerical Order (use actual dates)
Sequential Order (most recent at top)
___When you started second grade
___When you were born
___ When you started kindergarten
___When you learned to ride a bike.
___ When you learned to walk.
___ When you learned to read.
___ When you lost your first tooth.
___ Today’s date.
What is the Earth’s time scale?
The Geological time scale is a record of the life forms and geological events in Earth’s history.
Scientists developed the time scale by studying rock layers and fossils world wide.
Radioactive dating helped determine the absolute divisions in the time scale.
Division of the
Geological Time Scale
are subdivided into
are subdivided into
Era ----> Period ----> Epoch
E + P = EP
Organize the different time names in order from the longest to the shortest.
Epoch Era Period
_________ , _________ , ________
Why are there epochs during the Cenozoic Era but not in the other eras?
The four eras in Earth's history so far are ________, _________, ___________, __________
: A. The longest of the geologic time divisions with distinct characteristics- they end and begin with dramatic geological changes on Earth such as global ice ages or mass extinctions
A geologic time division with distinct characteristics that is shorter than an era and longer than an epoch – they generally end and begin with the appearance of new species or geological changes
The shortest of the geologic time divisions with distinct characteristics
Divisions of Geologic Time
Geological time begins with Precambrian Time. Precambrian time covers approximately 88% of Earth’s history.
PRE-CAMBRIAN – 88% of earth’s history
Paleozoic (ancient life)
544 million years ago…lasted 300 million yrs
Mesozoic (middle life)
245 million years ago…lasted 180 million yrs
Cenozoic (recent life)
65 million years ago…continues through present day
Today we are in the Holocene Epoch of the Quaternary Period of the Cenozoic Era.
Which unit is the largest?
Which unit is the smallest?
Paleozoic Era (Ancient Life)
The Cambrian period is the 1st period of the Paleozoic Era. “Age of the Trilobites”
Explosion of life in the oceans began during this era.
Most of the continents were covered in warm, shallow seas.
- Invertebrates were dominate - Trilobites
- Fish emerged during this time
- Fish led to the arrival of amphibians
The end of the Paleozoic era is called the “Age of Amphibians”
- Early land plants including mosses, ferns and cone-bearing plants.
- The early coal forming forests were also formed during this time.
Much of the limestone quarried for building and industrial purposes, as well as the coal deposits of western Europe and the eastern United States, were formed during the Paleozoic.
The Cambrian (beginning) opened with the breakup of the world-continent Rodinia and closed with the formation of Pangaea, as the Earth's continents came together once again.
This event is thought to have caused the climate changes that led to mass extinction event.
The Appalachian mountains were formed during this time.
At the end of the Paleozoic, the largest mass extinction in history wiped out approximately 90% of all marine animal species and 70% of land animals.
Possible causes of this Mass Extinction Event
Lowering of sea levels when the continents were rejoined as Pangaea (convergent boundary)
Increased volcanic activity (ash and dust)
Climate changes – cooler climate
Mesozoic Era – Middle Life
At the beginning of this era the continents were joined as Pangaea.
Pangaea broke up around the middle of this era.
Reptiles became the most abundant animals because of their ability to adapt to the drier climate of the Mesozoic Era.
Skin maintains body fluids
Embryos live in shells
Dinosaurs were also very active in this era.
First small dinosaurs appeared in the Triassic Period.
Larger and more abundant dinosaurs appeared in the Jurassic Period.
Small mammals and birds also appeared during this era.
The mammals were small, warm-blooded animals. Hair covering their bodies.
These characteristics help them survive in changing environments.
The main plant life of this time were Gymnosperms or plants that produce seeds, but no flowers.
Flowering plants appeared during the END of this era.
This era ended with a mass extinction event about 65 million years ago.
Many groups of animals, including the dinosaurs disappeared suddenly at this time.
Many scientists believe that this event was caused by a comet or asteroid colliding with the Earth.
Cenozoic Era – Recent Life
Began about 65 million years ago and continues today!!!!!
Climate was warm and mild.
Marine animals such as whales and dolphins evolved.
Mammals began to increase and evolve adaptations that allowed them to live in many different environments – land, air and the sea.
Grasses increased and provided a food source for grazing animals
Many mountain ranges formed during the Cenozoic Era
Alps in Europe and Himalayas in India; Rocky Mountains in the USA
Growth of these mountains may have helped to cool down the climate
Ice Ages occurred late in the Cenozoic Era (Quaternary Period).
As the climate changed, the animals had to adapt to the rise and fall of the oceans caused by melting glaciers.
This era is sometimes called the “Age of Mammals”
Marine animal examples:
Algae, Mollusks, Fish and Mammals
Land animal examples:
Bats, Cats, Dogs, Cattle and Humans
Humans are thought to have appeared around 3.5 million years ago (during the most recent period – Quaternary).
Flowering plants were now the most common plant life.