Geologic Time Scale and Their Characteristics PDF

Good morning !!! September 12, 2024  Exploring earth’s history MECHANICS: The class will be divided into two groups. Each group will be given a set of strips for them to arrange correctly the sequence of the Earth’s timeline and paste it on the board. The first group who finishes first and...

Good morning !!! September 12, 2024  Exploring earth’s history MECHANICS: The class will be divided into two groups. Each group will be given a set of strips for them to arrange correctly the sequence of the Earth’s timeline and paste it on the board. The first group who finishes first and have the most correct answer will be the winner. GEOLOGIC TIME SCALE AND their CHARACTERISTICs  LEARNING OBJECTIVES! At the end of the discussion, the students should be able to: 1. Recognize the relationship among the divisions- eons,eras, periods, and epochs. 2. Classify the life forms in what eras they belonged. 3. Create a simple concept map of the geologic time scale and other characteristics.  WHAT IS GEOLOGIC TIME SCALE ?  Geologic time scale The geologic time scale divides up the history of the earth based on life forms that existed during specific times since the creation of the planet. These divisions are called geochronologic units. ( geo: rock, chronology: time) Fossils can be remains or traces (tracks, burrows or other evidence of behavior) of organisms that lived on earth a long time ago. The fossil record is the only direct evidence scientists have of life that existed some hundreds or even millions of years ago. Inferences from fossils and rocks can lead to an idea of how ancient life was.  PALEONTOLOGISTS Scientists who reconstruct prehistoric life from plant and animal fossils. Like all geologists, paleontologists are limited to whatever they find in the rocks. Paleontologists use comparison and contrast method when making inferences about functions performed by body parts or ways by which the organism adapted to changes in environment.  Paleontologists noted that microscopic fossils are ideal because they are abundant, widespread and are sensitive to any change in the environment. LIMITATIONS: a. Not all organisms can turn easily into fossils. b. Many fossils are not yet located for thcy are buried way below. c. Many skeletons or shells of fossils have been damaged by groundwater, pressure and/or heat. d. Older time periods are represented by a few rocks because of burial or erosion. The Geologic Time Scale is divided by the following divisions: Period Era The concept of a Geologic Time Scale When "periods" are compacted is that a "period" is a basic unit of together according to their geological time during which a characteristics, this geologic division specific kind of rock system is will comprise the so-called "era." produced. Epoch Eon Some "periods" have their own When "eras" are grouped together, subdivision; these geologic this will create the longest geologic subdivisions are called "epochs." subdivision called an "eon." The four large units of geologic time scale are called eras. a. PreCambrian b. Paleozoic c. Mesozoic d. Cenozoic Precambrian  No life possible as the Earth initially forms 4.6 billion years ago. A. Hadeon Eon A. Hadeon Eon Oldest rocks form as the Earth cools. The atmosphere and oceans were also formed. b. archean Eon  B. ARCHEAN Eon The photosynthesizing cyanobacteria appeared ( first unicellular). How did life forms look like 3.3 billion years ago ? Scientists believed that they look like: Blue-green algae Bacteria  After about 200 million years The blue-green algae formed larger mats that grew one on top of the other During the next 1.2 billion years Bacteria grew into colonies. C. PROTEROZOIC Eon C. PROTEROZOIC EON After 2.6 billion years, the first multicellular soft- bodied animals appeared. A group of jellyfish, corals, worms, and mollusks started appearing.  Towards the end of the Precambrian , the land became covered with glacial ice, grinding everything in its downhill movement. PALEOZOIC ERA A. cambrian period The Age of Trilobites The beginning of the Paleozoic Era. The explosion of life. Abundance of hard-shelled trilobites, a few brachiopods, echinoderms, sponges and sponge-like organisms were found during this period.  b. Ordovician Period Some strange-looking fishes appeared. The first vertebrates appeared during this period. Areas of land were jutting from the sea but these were still barren. b. Ordovician Period c. Silurian period The Age of Corals The first land plants which were very small began to grow. Scorpion-like arachnids (first fossil land animals) soon followed.  c. Silurian period The first jawed fish was seen during this period. Coral reefs expand and land plants begin to colonize barren land. Towards the end of this period, trilobites were on the decline.  D. DEVONIAN period The Age of Fishes. Predatory fishes like sharks and bony fish have existed. The land began taking a new appearance- swamps and forests appeared. D. DEVONIAN period Towards the late Devonian Period, amphibians were moving on land. Land vertebrates were predominant. Ex. Ichthyostega ( predecessor of the modern frog).  E. Mississipian and Pennsylvanian Periods Swampland forests covered much of the land. The plants that grew and died were buried and changed to coal in great amounts. These periods are also known as the Carboniferous time.  E. Mississipian and Pennsylvanian Periods Several dragonflies, cockroaches, and other winged insects were abundant. The first reptiles also appeared at this time.  F. PERMIAN period Age of Amphibians. The land was by then thickly forested with many kinds of trees, none of which were flowering. F. PERMIAN period Land animals such as amphibians, reptiles, and insects were abundant.  F. PERMIAN period If representatives of these hardy organisms still live today they are called living fossils. However, some have died out without leaving any descendants- extinct. Examples of those which have been extinct are the lycopod trees, seed fern trees, trilobites, and brachiopods. MESOZOIC ERA  A. TRIASSIC Period In this era, the first dinosaurs appeared. Mollusks had a worldwide distribution but became extinct after some time. These mollusks were a distant relative of the modern day squid. A. TRIASSIC Period Land masses were still populated by insects and plants. Newer kinds of animals appearing were the chicken-size and dog- size dinosaurs and small rodents during the late-Triassic Period. The Pangea break apart during this period. B. JURASSIC Period Golden Age of Dinosaurs. Dinosaurs became the largest land dwellers. The first true bird (Archaeopteryx) also appeared with feathers, large brains, with teeth structurally similar to small dinosaurs. c. cretaceous Period Extinction of Dinosaurs. The large plant-eating dinosaurs existed with moderate-sized meat- eating dinosaurs. Soon reef-forming clams disappeared. Most swimming reptiles as well as dinosaurs disappeared too. CENOZOIC ERA a. TERTIARY Period It became cooler and conebearing evergreens began to proliferate. Marine organisms increased in number and kind. Fish and mammals became abundant, too. As the Tertiary Period progressed, mammals increased in size and began looking like hominid. The Tertiary Period ended and the Quarternary Period began. There were two epochs : Pleistocene and Holocene. a. Pleistocene Epoch Ice Age began During this period also, the first human appeared. Glaciers grew and melted several times causing changes in land environment, sea level and water temperature. B.Holocene Epoch The Age of Man. Ice Age ends. The recent era belongs to this epoch. In this era, the humans flourished and become the dominant.  SUMMARY The geologic time scale is the “calendar” for events in the Earth history. It subdivides all time into eons, eras, periods, and epochs. The emergence of and disappearance of species from the fossil record typically are used to mark the beginnings and endings of most eras, periods, and epochs. THANK YOU !!!