“A Trip Through Geologic Time” CHAPTER 20 “A Trip Through Geologic Time”

p. 613: 1. What are the 4 eras of geologic time? Precambrian, Paleozoic, Mesozoic, and Cenozoic

2. How is a geologic period different from an era? An era is the longest division of geologic time. It is broken down in to smaller divisions called periods. Much like a year is broken down into small divisions called months….and months are broken down into small divisions called days….

3. What occurred on Earth 4.6 billion years ago? (This is the beginning of Earth as we know it). Earth was a planet of very hot, molten rock with many volcanic eruptions. The atmosphere consisted mainly of poisonous gases. This was the beginning of the Precambrian era.

4. Look at figure 20-3. What seems to be the major trend in development of life forms during geologic time? The life forms develop from very simple (jellyfish, corals, clams) to more complex (wooly mammoths…man)

Section 20-1: “The Geologic Time Scale” Scientists have established the geologic time scale to divide geologic time into workable units. 2. Earth’s history is divided into 4 geologic eras: PRECAMBRIAN ERA, PALEOZOIC ERA, MESOZOIC ERA and CENOZOIC ERA.

Divisions An ERA is the LARGEST division of the geologic time scale. Eras are broken into small subdivisions called PERIODS. Eras are of DIFFERENT lengths. Pre-cambrian Era Paleozoic Era Mesozoic Cenozoic

Early Earth History “Precambrian Era” The LONGEST era lasting about 4 billion years. Accounts for about 87% of Earth’s history. “The DAWN OF LIFE” Rocky shorelines with no life on land Climate: Fiery and HOSTILE climate. POISONOUS gases in the atmosphere.

Precambrian (continued) Life: Found only in the SEAS AND TIDEPOOLS Earliest living organisms are: BACTERIA and BLUE-GREEN ALGAE First fossils ever found were of BACTERIA First animal life found at the end of this era: Invertebrates like JELLYFISH and WORMS, SPONGES and CORALS

Precambrian Land Land: IGNEOUS rocks Mountain building – granite mountain ranges “SHIELDS” are the oldest rocks on earth Half of our mineral deposits are found near these mountain ranges: IRON, COPPER, NICKEL, GOLD AND SILVER.

Paleozoic Era Life: Creatures of the Paleozoic seas: SHELLS, starfish, FISH, brachiopods, and TRILOBITES. 1st vertebrate is the FISH Fossils found (exoskeletons, vertebrates) Life comes ashore – Life on land: Huge forests of ferns and sago palm CYCADS are among the first seed plants. These forests formed the huge COAL deposits in the United States IMPORTANT INDEX FOSSIL: TRILOBITE

Paleozoic Era “Life continues” 1.AMPHIBIANS the first land vertebrates. Means “ living a DOUBLE-LIFE spending early lives in water and then moves to land Example: is the Eryop REPTILES with tough skin, scales, leather eggs and hard plates develop. Alligators, wasps, beetles exist

Paleozoic Land Climate: Warm and HUMID at the beginning of the era; flooding often. Climate cools later Land: Mountains rising in parts of North America (Appalachian mountains), Norway, Scotland and Greenland

20-3: Middle and Recent Earth History Mesozoic divided into 3 PERIODS. 1. TRIASSIC 2. JURASSIC 3. CRETACEOUS This era is a period of many CHANGES both in the land and in the living things that inhabit the earth.

Mesozoic Era PANGAEA broke apart Numerous earthquakes and VOLCANIC eruptions throughout this era. Many mountains formed at this time: Sierra Nevada, and the Rocky Mountains

Triassic Period Life: Large reptiles that have lungs and breathe air have returned to the SEAS MAMMALS appear: have fur, offspring do not hatch from eggs; young grow and mature in mom’s body before birth Ferns and seeds still common. Cycads are now BIGGER. Very first small DINOSAURS (no bigger than chickens) appear

Triassic Period Land and Climate North and South America begin to SEPARATE FROM AFRICA Narrow sea opens between North America, and Europe known as the ATLANTIC OCEAN Southern lands still joined: Africa, South America, Antarctica and India Climate: DROUGHT exists Hotter than ever before

Jurassic Period Life: “Age of the DINOSAURS” Huge CYCADS and modern-looking evergreens called CONIFERS make up the forests First BIRD - Archaeopteryx Climate: Dry and WARM Land: “Supercontinent” Animals and plants are similar VOLCANOES active in the American West

Cretaceous Period Time of rapid “ ______________” Life: Dinosaurs __________(Tyrannosaurus, Triceratops) Herbivores and ____________ Only crocodiles, turtles, lizards and ________ survived from earlier periods. __________ plants appeared (magnolia, oak, fig, poplar, and elm) Most of the great tree ferns and cycads ______________ Mass _________________ occurred at end of period

Cretaceous Land and Climate Time of widespread FLOODING. Continents continue to spread APART North America and Europe are still joined At end of period – sea levels dropped; rivers and flood plains dried up. Climate: Why was there a mass extinction of life? Drastic change: CLIMATE change Disease Gigantic ASTEROID crashed into Earth

Cenozoic Era This is the era in which we live today Divided into 2 periods (Tertiary and Quaternary) Tertiary Life: Grassy meadows; groups of REDWOODS, oaks and cedar trees. Birds singing; “Unita beasts” (ancient rhino) First HUMAN LIKE creatures begin walking upright on the African plains. “Lucy” – 1 meter tall Climate: Mild climate throughout this period Land: Himalaya Mountains rise; Grand canyon formed

Quarternary Period Climate: Sharply colder; ICE Age Great sheets of ice from Arctic and Antarctic advance and cover one-FOURTH of the land on earth Last ice age ended 11,0000 years ago World warms; FARMING becomes widespread and modern civilization begins Life: First modern HUMAN BEINGS APPEAR, wooly mammoths die out