Geological Time Scale

Understanding of Earth’s Tectonic and Structural Evolution through
Geological Time Scale

1. Mithun Ray Department of Geography Malda College (University of Gour Banga ) E-mail: [email protected] Understanding of Earth’s Tectonic and Structural Evolution through Geological Time Scale

2. Units of Time 1000 milliseconds = 1 second 60 seconds = 1 minute 60 minutes = 1 hour 24 hours = 1day 7 days = 1 week 28, 29, 30 or 31 days = 1 month 365 or 366 days = 1 year 12 months = 1 year 10 years = 1 decade 100 years = 1 century 1000 years = 1 millennium

3. ONES HUNDRED THOUSAND LAKH MILLION CRORE BILLION TRILLION Numbering System

4. What is Geological Time Scale A system of chronological dating that classifies geological strata in time A Calendar for events in Earth History A record of the major events and diversity of life forms present in Earth’s history.

5. Constructing Evidences of Geological Time Scale Field observations Fossil records Stratigraphic correlations Radioactive dating Palaeomagnetic orientations Orbital revolution of the Earth and The rotation of the earth.

6. Major Incidences accounted in Geological Time Scale Mass extinctions, Appearance of new species or genera of life, Mountain-building movements Drifting of continents Spreading of ocean floors Widespread glaciations Dominance of certain species Massive migration of life between land and water

7. From the time of Hutton, scientists were convinced that the earth was much older than the 6000 years predicted by the religious scholars. The oldest rocks found so far on Earth (based on zircon grains from Australia) have been dated at 4.1-4.2 billion years. Meteorites have also been dated at 4.6 billion years. Meteorites are considered to be remnants of a plant or asteroid that originally formed at the same time as the Earth, so that the Earth’s age is currently estimated to be 4.6 billion years. The oldest fossils are preserved remains of stromatolites , which are layers of lithified blue-green algae, dating to approximately 3.5 billion years before present. Age of our Planet ? 16 Table of Contents

8. Units of Geological Time Scale Duration of half a billion years (or) more time EON ERA PERIOD EPOCH AGE Duration of Millions of years Duration of Tens of Millions of years Duration of hundreds of millions of years Duration of several hundred millions of years

9. EON / AEON Aeon শব্দটি গ্রীক শব্দ “ Aion ” থেকে এসেছে যার অর্থ “জীবনকাল” Phanerozoic Archean Greek word “ Cryptos ” means “Hidden” “” Zoion ” means “Living being” / “Life” Greek word “ Phaneros ” means “ Vissible ” “” Zoion ” means “living being” / “life” Proterozoic CRYPTOZOIC

10. CRYPTOZOIC [ Also known as “Pre-Cambrian” ] Span of time between 4000 mya and 540 mya Archean Eon Proterozoic Eon ### HADEAN EON ### 4600 mya to 4000 mya As of 2016, International Commission on Stratigraphy describes its status as “informal”. Geologist Preston Cloud coined the term in 1972, originally to label the earliest rocks on earth.

11. (A) ARCHEAN EON The oldest era of the earth ( between 4000 mya and 2500 mya ) The word “ archean ” comes from the Greek word “ arkhe ” which means “ beginning ” or “ origin ” The Oldest Rock Formations exposed on the surface of earth ( Canadian Shield, Baltic Shield, Peninsular India, African Shield etc.) Formation of Greenstone Belts Origin of life, especially the prokaryotes, bacteria and blue-green algae

12. (B) PROTEROZOIC EON Between 2500 mya and 540 mya Dry and Cold climate Origin of Eukaryotic cells and multi-cellular life Occurrence of earliest known fossils including of soft-bodied marine invertebrates

13. (C) PHANEROZOIC EON 540 MYA TO PRESENT Older Younger

14. (I) PALEOZOIC ERA Older Younger Between 540 mya and 245 mya

15. (a) Cambrian Period Between 540 mya and 505 mya Age of trilobites ( Marine invertebrates ) Supercontinent Gondwana forms near the South Pole (note position of present-day Florida) Existence of plants was observed only as algae Absence of land plants.

16. (b) Ordovician Period Between 505 mya and 438 mya Age of Graptolites First vertebrates originated as jawless fishes All plants and animals still restricted to water Four main continents: Gondwana , Baltica , Siberia and Laurentia First fungi originated

17. (c) Silurian Period Between 438 mya and 408 mya First land plants appear and land animals follow Laurentia collides with Baltica and closes Iapetus Sea Dominance of Sea lilies, eurypterids and land scorpions Origin of the earliest Vascular Plants on earth

18. (d) Devonian Period Between 408 mya and 360 mya Age of the Fish Pre- Pangea forms Extinction of primitive vascular plants happened Origin of modern Vascular plants with true leaves, roots and stems Violent volcanic eruptions and crustal movements

19. (e) Carboniferous Period Between 360 mya and 286 mya It is known for its coal deposits First land vertebrates First Reptiles laid eggs with shells in this period. Highest ever atmospheric oxygen levels seen on earth was in this period.

20. (f) Permian Period Between 286 mya and 245 mya Pangea forms. Reptiles spread across continents. Widespread aridity on one side and Glaciation at the other side. Extinction of Palaezoic Plants and invertebrates (251 Mya).

21. (II) MESOZOIC ERA Older Younger Between 245 mya and 66 mya

22. (a) Triassic Period Between 245 mya and 208 mya Formation of Salt, Gypsum and red beds First dinosaurs, turtles, lizards appear Pangaea still in existence Climate arid Modern Corals appeared

23. (b) Jurassic Period Between 208 mya and 144 mya Great plant eating dinosaurs were in existence- “Golden age of dinosaurs” Appearance of the first frogs, salamanders, crocodiles, flying reptiles and birds were noticed Breakup of Pangaea into Gondwana and Laurasia happened during this period only

24. (c) Cretaceous Period Between 144 and 66 Mya. First snakes appear First flowering plants Deciduous trees and grasses common This is the last period of the age of Dinosaurs Breakup of Gondwana

25. (III) CENOZOIC ERA Older Younger From 66 mya to Present EPOCH

26. Older Younger EPOCH (a) Tertiary Period Between 65 mya and 2 mya

27. ( i ) Paleocene Between 65 mya and 55 mya First horses appear Tropical plants dominate Climate Tropical

28. (ii) Eocene Between 55 mya and 38 mya Whales, rhinos, elephants and other large mammals develop. Reglaciation in South Pole First Grasses Appeared

29. (iii) Oligocene Between 38 mya and 25 mya Dogs and cats appear Early ancestral elephants Warm but cooling climate

30. (iv) Miocene Between 25 mya and 5 mya Extensive glaciation in Southern Hemisphere Horses and Mastodons diverse First Apes appeared Spread of grasslands as forests contracted

31. (v) Pliocene Between 5 mya and 2 mya Ice Age begins Seas restricted The Grand Canyon Forms Cool and dry climate First known appearance of hominids (human like primates)

32. Older Younger EPOCH (b) Quaternary Period 2 mya to Present

33. ( i ) Pleistocene Between 2 mya and 0.01 mya Ice sheets are predominant- Ice age Glacial climate Four great ice advances and retreats Modern humans develop Formation of large scale Deserts – Sahara was formed

34. (ii) Holocene Since 10,000 years ago Rise of human civilization Beginning of Agriculture Copper Age 3500 BC Bronze Age 2500 BC Iron Age (1200 BC) Man used iron implements in 1350 BC

35. We are living in Meghalayan Age of Holocene Epoch of Quaternary Period of Cenozoic Era of Phanerozoic Eon

36. Now the question is How to remember this! To remember the sequence of ERA s you have to keep in your mind the following sentence: Please Pay My Children P lease P ay M y C hildren Pre-Cambrian Paleozoic Mesozoic Cenozoic Younger Older

37. In case of PERIOD s you have to remember Camels Often Sit Down Carefully Perhaps Their Joints Creak C amels O ften S it D own C arefully P erhaps T heir J oints C reak Cambrian Silurian Devonian Carboniferous Permian Triassic Jurassic Cretaceous Ordovician Paleozoic Era Mesozoic Era Younger Older

38. In case of EPOCHs you have to remember Put Eggs On My Plate, Please Honey P ut E ggs O n M y P late P lease H oney Paleocene Oligocene Miocene Pliocene Pleistocene Holocene Eocene Tertiary Period Quaternary Period Younger Older

39. What if Geologic Time was the span of your arm?

40. This Power Point Presentation (PPT) has been prepared especially for Undergraduate Students. The materials (Maps, Diagrams and Images) used in this presentation were collected and compiled mainly from variours academic blogs, research papers, books etc. The author has designed this PPT according to his convenience to deliver the lecture.

41. THANK YOU