Presentation on theme: "How do we know when things happened?"— Presentation transcript:
1How do we know when things happened? Geologic timeHow do we know when things happened?
2GoalsStudents will write about, talk about, and understand the principles of relative dating and original horizontality(7A)Students will write about, talk about, and understand the principle of Radiometric dating 7B)Students will write about, talk about, and understand the scale and scope of the Geologic time scale
3Part 1With a partner of your choosing, answer the questions from the end of the packet I hand out. Alternate answering the questions on you answer page.Skip questions 1 and 15.Match vocabulary words to the questions to help find answers if you are having trouble with one.5. 26617, , 281
4Events in Your Life ___When you started second grade 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.
6What 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.
7Divisions of Geologic Time Eras are subdivided into periods...periods are subdivided into epochs.EraPeriodEpochE + P = EP
8Divisions of Geologic Time Geological time begins with Precambrian Time. Precambrian time covers approximately 88% of Earth’s history.
10FOUR Eras… PRE-CAMBRIAN – 88% of earth’s history Paleozoic (ancient life)544 million years ago…lasted 300 million yrsMesozoic (middle life)245 million years ago…lasted 180 million yrsCenozoic (recent life)65 million years ago…continues through present day
11Today…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?
13Paleozoic 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 dominant - TrilobitesFish emerged during this timeFish led to the arrival of amphibiansThe 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.
14Trilobites Lived in Earth’s ancient seas Extinct before the dinosaurs came into existenceCambrian Period is know as the “Age of the Trilobites”
15Paleozoic EraMuch 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.
16Paleozoic EraAt 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 EventLowering of sea levels when the continents were rejoined as Pangaea (convergent boundary)Increased volcanic activity (ash and dust)Climate changes – cooler climate
21Mesozoic 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 fluidsEmbryos live in shells
22Mesozoic Era 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.
26Mesozoic EraThe main plant life of this time were Gymnosperms or plants that produce seeds, but no flowers.Pine TreesFlowering plants appeared during the END of this era.
27Mesozoic EraThis 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.
32Mesozoic Era – Mass Extinction Event Asteroid or Comet collides with Earth.Huge cloud of smoke and dust fills the airBlocks out sunlightPlants dieAnimals that eat plants dieAnimals 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.
37Mesozoic PlantsFlowering plants evolved towards the end of the Mesozoic Era.
38Cenozoic 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 animalsMany mountain ranges formed during the Cenozoic EraAlps in Europe and Himalayas in India; Rocky Mountains in the USA
39Cenozoic EraGrowth of these mountains may have helped to cool down the climateIce 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”
40Cenozoic Era Marine animal examples: Land animal examples: Algae, Mollusks, Fish and MammalsLand animal examples:Bats, Cats, Dogs, Cattle and HumansHumans 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.