The Geological Time Scale Recognize the relationship among the units—era, epoch, and period—into which the geologic time scale is divided Illustrate the vast diversity of life that has been present on Earth over time by using the geologic time scale Summarize how scientists study Earth’s past environment and diverse life- forms by examining different types of fossils (including molds, casts, petrified fossils, preserved and carbonized remains of plants and animals, and trace fossils) Explain how Earth’s history has been influenced by catastrophes (including the impact of an asteroid or comet, climatic changes, and volcanic activity) that have affected the conditions on Earth and the diversity of its life-forms.

Events in Your Life ___ When you started fifth 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. In your notebook, 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: 1)Numerical Order (use actual dates) 2)Sequential Order (most recent at right) 11/30

Unit 4 Geologic Time –Age of the Earth (models) –Eons, Era, Periods, Epochs –Soil/Rock Layers –Fossil Records –Radioactive Dating

For you to do: Color in the spiral time line and cut out the general shape. Glue the timeline in your notebook, we will use this as a reference.

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.

Divisions of Geologic Time Eras are subdivided into periods...periods are subdivided into epochs. Eon  Era Period Epoch E + P = EP

Today… 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?

Divisions of Geologic Time Geological time begins with Precambrian Time. Precambrian time covers approximately 88% of Earth’s history.

FOUR Main Eras… 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

ERAS Guided Notes Flora – Plants Fauna – Animals All dates are approximate. Paleozoic: +/- 10 million years Mesozoic: +/- 5 million years Cenozoic: +/- 1-2 million years As we gather new DATA, the numbers can change.

Precambrian Hadean Started 4600 million years ago –4.6 billion years ago Formation of Earth Oldest dated meteorites – 4.6 billion years First rock formation

Precambrian Archaean Started 3800 million years ago –3.8 billion years ago First unicellular organisms

Precambrian Proterozoic Started 2500 million years ago –2.5 billion years ago First multicellular organisms Primitive water plants, algae

Paleozoic

Paleozoic Cambrian Period Started 545 million years ago First animals with shells/bones Trilobites dominated First water plants

Paleozoic Ordovician Period Started 470 million years ago First fishes First land plants Invertebrates dominated

Paleozoic Silurian Period Started 443 million years ago Fishes dominated Water animals began breathing out of water. Wind carrying seed plants

Paleozoic Devonian Period Started 417 million years ago Fishes dominated First amphibians (walk on land) First insects Swamps

Paleozoic Mississippian Period Started 354 million years ago Age of amphibians Sharks dominated waters Large swamps and trees

Paleozoic Pennsylvanian Period Started 334 million years ago Age of reptiles Great coal forests (conifers)

Paleozoic Permian Period Started 293 million years ago Reptile dominated Insects Ended with massive extinction. End of Trilobites and many marine animals.

Paleozoic Era (Ancient Life) The Cambrian period is the 1 st 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.

Paleozoic Era 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.

Trilobites Lived in Earth’s ancient seas Extinct before the dinosaurs came into existence Cambrian Period is know as the “Age of the Trilobites”

Brachiopods Marine animals that resemble clams.

Early Fish Early fish did not have jaws. Some species of sharks were in existence at this time.

Frilled Shark that was found in Japan in January This shark was considered a “living fossil”

Early Land Plants Cone bearing plants Ferns Mosses

Paleozoic Era 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. –P–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

Snowball Earth Rodinia supercontinent effected the ocean currents, causing global cooling.

Mesozoic

Mesozoic Triassic Period Started 248 million years ago First warm blooded dinosaurs Abundant conifers

Mesozoic Jurassic Period Started 205 million years ago First mammals First birds Dinosaurs present

Mesozoic Cretaceous Period Started 144 million years ago First flowering plants / fruits Dinosaurs dominated (ended with the C-T extinction)

The timespan between a Tyrannosaurus Rex (Cretaceous) and human is closer than a T-Rex and a Stegosaurus (Jurassic). 65 million years 83 million years

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. –S–Skin maintains body fluids –E–Embryos live in shells

Mesozoic Era Dinosaurs were also very active in this era. –F–First small dinosaurs appeared in the Triassic Period. –L–Larger and more abundant dinosaurs appeared in the Jurassic Period. Small mammals and birds also appeared during this era. –T–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. –Pine Trees Flowering plants appeared during the END of this era.

Mesozoic 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.

Crater sites on Earth

Dinosaurs

Mesozoic Reptiles

Mesozoic Mammals

Mesozoic Plants Flowering plants evolved towards the end of the Mesozoic Era. This allowed pollination to occur via animals (instead of relying on wind – very little wind in dense forests).

Mesozoic Era – Mass Extinction Event Asteroid or Comet collides with Earth. –Huge cloud of smoke and dust fills the air –Blocks out sunlight –Plants die –Animals that eat plants die –Animals that eat plant-eaters die. However, not all forms of life died during this event. Many animals that you see today are descendants from the survivors of this extinction event.

Cenozoic

Cenozoic Tertiary Started 65 million years ago Started with extinction of dinosaurs First placental mammals Deciduous Forest Dominates Age of Mammals

Cenozoic Quaternary Started 2.4 million years ago Age of Human Deciduous Forests Grasslands and Savannahs

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

Cenozoic Era 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”

Cenozoic Era 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.

Cenozoic Mammals

Flowering Plants were common during the Cenozoic Era