Page 143: Geologic Time
Divide pages 144-147 in 6 One for each box: Hadeon Eon Archeon Eon Cambrian Period Ordovician Period Silurian Period Devonian Period Carboniferous Period Mississipian Period Pennsylvanian Period Permian Period Triassic Period Jurassic Period Cretaceous Period Paleogene Period Paleocene Epoch Eocene Epoch Olligocene Epoch Neogene Epoch Miocene Epoch Pliocene Epoch Pleistocene Epoch Holocene Epoch
Geologic Time Remember that geologic time is based on evidence from rocks We use absolute dating to determine the absolute age of certain rock layers We also use relative dating to help determine the story of the earth Geologic time scales are a sequence of events pieced together using evidence from absolute and relative dating methods
Geologic Time Scale Earth s history is divided into units of time that make up a geologic time scale.
Geologic Time Scale The geologic time scale is a visual record of Earth s history, with the individual units based on changes in the rocks and fossils.
The time scale is divided into four major subdivisions: Eons Eras Periods Epochs
Eons Eons Longest subdivisions Based on abundance of fossils
Eras Eras Marked by the significant worldwide changes in the types of fossils present in rock
Periods Periods Based on the types of existing life globally at a particular time Named by geologists from places around the world where they found certain fossils and rocks
Epoch Epochs Divided periods characterized by differences in life forms
Page 145: Early Earth
Scientists hypothesize that the Earth is 4.6 billion years old
Atmosphere Early Earth Composed of hydrogen and helium Later Precambrian Earth Volcanic eruptions released carbon dioxide, water vapor, and nitrogen
Oceans Early Earth Earth s surface too hot All water evaporates Later Precambrian Earth Earth cools, water vapor condenses
Continents Early Earth Earth s rocks started cooling and hardening Less dense rock at surface formed landmasses Later Precambrian Earth Old continents break apart New continents form as a result of continental drift
Before earth existed, a cloud of gas, ice and dust called nebula floated in space
Gravity pulled the particles together and formed the sun. The remaining particles eventually formed the other planets
Earth became larger as more particles came together. These collisions produced thermal energy
Beginning of time geologic time Geological time begins with a long span of time called Precambrian Time, which covers about 88 percent of Earth s history and ended about 544 million years ago.
Precambrian Time During the first several hundred million years of Precambrian Time, an atmosphere, oceans and continents began to form. During Precambrian Time (4.6 billion 544 million years ago): very few fossils remain from this time Precambrian rocks have been buried, causing fossils to be changed by heat and pressure most Precambrian organisms lacked hard parts
Early life forms Earliest life form to appear was cyanobacteria, or blue-green algae which added oxygen to the atmosphere through photosynthesis
Early life forms Jellyfish also appeared during the Precambrian time
Precambrian Time to Present The time between Precambrian Time and the present is divided into three long units called eras: Paleozoic Era Mesozoic Era Cenozoic Era
The Hadean Eon: Hadean Eon The first 640 million years of Earth When Earth became hot enough to melt metal, the denser metal began to flow because of gravity. This is how earth got its different layers
The Hadean Eon The earth began to cool and small islands of solid rock formed and floated on the molten sea of lava. As it continued to cool the molten sea started to solidify forming an ancient crust
The Hadean Eon Volcanic eruptions produced gases that began to form the Earth s atmosphere.
The Archean Eon: 4 to 2.5 million years ago With the earth still cooling and extensive volcanic activity the continental crust and oceanic crust were formed.
The Archean Eon As the temperature in the atmosphere dropped, water vapor in the air condensed. Rain began to fall along and oceans were formed.
The Archean Eon Fossil bacteria and Stromatolites were some of the earliest evidence of life.
The Phanerozoic Eon: 542 million years ago to the present visible Life Continents were breaking apart Temperatures were increasing Sea levels were rising
The Phanerozoic Eon This eon set the stage for adaptations and extinctions
The Phanerozoic Eon Adaptation Characteristics that species develop over time that help them survive in a particular environment.
The Phanerozoic Eon Extinction A species is considered extinct when all of its members have died.
The Phanerozoic Eon Asteroids that collide with Earth can cause changes in the Earth s environment. Some of these changes can be so large that is can cause mass extinction of species. These changes happened and the species could not adapt to the changes so they died off.
The Phanerozoic Eon The Phanerozoic Eon is characterized by three eras: Paleozoic era oldest era divided into six periods Pangea forms Mesozoic era middle era divided into three periods Dinosaurs, small mammals, birds Cenozoic era youngest era divided into two periods Current era
The Proterozoic Eon: 2.5 to 0.542 billion years ago Oxygen began to increase during this time The Great Oxygenation Event
The Proterozoic Eon Life was still restricted to the water but an important change happened near the end of this eon. The first multicellular organisms formed
Paleozoic Era PALEOZOIC ERA 544 million years ago to 245 million years ago
The Phanerozoic Eon The Phanerozoic Eon is characterized by three eras: Paleozoic era oldest era divided into six periods Mesozoic era middle era divided into three periods Cenozoic era youngest era divided into two periods
Early Paleozoic Era Early Paleozoic consists of the Cambrian and Ordovician periods often called Age of Invertebrates continents covered by large, shallow inland seas no life existed on land; Ordovician period ended with mass extinction
Middle Paleozoic Middle Paleozoic consists of Silurian and Devonian periods often called Age of Fishes some invertebrates lived on land (cockroaches/dragonflies) continents colliding forming mountain ranges
Late Paleozoic Late Paleozoic consists of Carboniferous and Permian periods Age of Amphibians (reptiles evolved from amphibians) continental collisions led to formation of Pangaea largest mass extinction occurred, reason under debate
The Cambrian Period Often referred to as the Cambrian explosion Lots of diverse organisms Organisms formed hard parts (ex: shells and bones)
The Cambrian Period Scientists hypothesized that the Cambrian explosion resulted from changes in Earth s environment Continents breaking apart Temperatures began to increase Sea levels rise (producing warm, shallow seas)
The Ordovician Period Marked by the appearance of the oldest complete vertebrate fossils (mostly jawless, armored fish) Diverse trilobites and jawless, armored fish Some corral fossils are found from this period Reef ecosystems mostly composed of algae and sponges Early land plants
The Silurian Period Wide and rapid spread of jawless fish First known appearance of freshwater fish fossils and jawed fish fossils Trilobites and ancient mollusks also existed First clear evidence of life on land although fossils are incomplete and difficult to interpret
The Devonian Period Earliest vascular plant fossils Two major animal groups on land: Tetrapods (land living vertebrates) Arthropods (wingless insects and spiders) 3 major continental masses: North America, Europe, Siberia near the equator
The Carboniferous Period Rich deposits of coal formed from plants during this time period Broken into two different epochs in the US because of the difference in the environments: Mississippian Pennsylvanian
The Mississippian Epoch Tropical and humid climate Mostly marine life Seasons were indistinct We know this because plants from this time period have no growth rings Earth was mostly water except for Pangea, where all land life was confined to
The Pennsylvanian Epoch Terrestrial and marine Decline of sea levels due to glaciers Lots of forests River deltas and floodplains led to increased land life and destroyed most marine environments This epoch is when most coal beds were formed
The Permian Period Period of great change Largest mass extinction recorded in Earth s history More than 90% of earth s life was destroyed Affected marine life more than land Led to the age of the Dinosaurs Fern-like plants that once dominated were replaced by plants that carried seeds Scientists are unsure why Could be glaciation, climate, or volcanoes
Mesozoic Era MESOZOIC ERA 245 million to 65 million years ago often called the Age of the Reptiles contained the Triassic, Jurassic and Cretaceous periods dinosaurs dominated, small mammals and birds appeared flowering plants (angiosperms) appeared Pangaea separated into continents, oceans began to form mass extinction from large meteorite impact scientists believe
Triassic Period First appearance of dinosaurs Earth was still in one land mass, Pangea It stretched from pole to pole with a large desert in the middle Most dinosaurs were on 2 legs and carnivorous Mostly warm and dry although there were some monsoons At the end of this period, plate tectonics picked up
Jurassic Period First large birds Large herbivores on four legs T-Rex did not appear until the very end of the Jurassic period Meat eaters during this time period included: Allosaurus, small, fast coelurosaurs, and Dilophosaurus Contrary to popular belief, no palm trees or flowering plants existed during this time Plant life included: Ferns, pines, redwoods, and cypresses
Cretaceous Period First flowering plants appeared Modern insects began to diversify Most famous extinction: Killed off most species of dinosaurs Other organisms survived: Flowering plants, snails and clams, amphibians, lizards and snakes, crocodiles, and mammals all survived
Cenozoic Era CENOZOIC ERA 65 million to present Early in Tertiary period, India collided with Asia to form Himalayas, Africa and Europe collided to form Alps; Cascades and Sierra Nevadas began to form in North America new grasses and flowering plants dominated land mammals continued to evolve Homo sapiens, or humans appeared about 400,000 years ago we live in the Holocene epoch of the Quaternary period
Paleogene Period Divided into six epochs: Paleocene Eocene Oligocene Neogene Miocene Pliocene Time of most diversity among mammals Periods of drastic global temperature change (ice age to hot)
Paleocene Epoch Started with the mass extinction of the cretaceous Paleocene-Eocene Thermal maximum: Extreme changes in climate and carbon cycling (lots of things die and are buried)
Eocene Epoch Oldest known fossils of modern day mammals appeared Thought to have the highest mean annual temperatures (above 30 0 C) Ocean currents changed, greater seasonality More larger mammal fossils Open savannah vegetation, reduction in forests
Oligocene Epoch Age of cooling Horses, deer, camel, elephants, cats, dogs, and primates dominated the land More savannah-like on land Marine species moved northward towards the poles
Neogene Period Divided into two epochs: Miocene Pliocene Dominated by mammals and birds Global cooling
Miocene Epoch Slight position change of continents Globally warmer climates Mountain building led to increase of grasslands, deserts, and tundra Age of fast-running herbivores and large predatory mammals and birds
Pliocene Epoch Joining of North and South America Mass migrations of armadillo, sloth, and porcupines Climate became cooler and drier Mediterranean sea almost completely dried up Forests turned into grasslands
Quaternary Period Divided into two epochs: Pleistocene Holocene Continents had roughly reached the same position they are today Ice ages come and go Dominated by humans
Pleistocene Epoch Time of the mammoth, saber-tooth cats, giant sloths, and other large mammals Global cooling (ice ages) Most of Earth covered in glaciers Exposed land bridges allowing populations to cross continents
Holocene Epoch Time since the last little ice age