Essential Question: summarize the development of the geologic column and its Major units of time 18.1 The Geologic Time Scale Homework: 5/8 vocabulary page 360 – define and give one fact 5/6 section review page 346

18.1 The Geologic Time Scale geologic column an ordered arrangement of rock layers that is based on the relative ages of the rocks and in which the oldest rocks are at the bottom. ► Evidence of changing conditions on Earth’s surface is recorded in the rock layers of Earth’s crust. ► The geologic time scale outlines the development of Earth and of life on Earth.

The Geologic Column ► Rock layers in a geologic column are distinguished by the types of rock the layers are made of and by the kinds of fossils the layers contain. ► Fossils in the upper layers resemble modern plants and animals. ► Many of the fossils discovered in old layers are from species that have been extinct for millions of years.

Divisions of Geologic Time ► The geologic history of Earth is marked by major changes in Earth’s surface, climate, and types of organisms. ► Geologists use these indicators to divide the geologic time scale into smaller units. ► Rocks grouped within each unit contain similar fossils and each unit is generally characterized by fossils of a dominant life-form.

Earth-History Clock ► Eon  Era ► Period  Epoch

Eons ► The largest unit of geologic time is an eon. Geologic time is divided into four eons: the Hadean eon, the Archean eon, the Proterozoic eon, and the Phanerozoic eon. ► the Hadean eon, the Archean eon, the Proterozoic eon = Precambrian Time. This 4 billion year interval contains most of Earth’s history.

Eras era a unit of geologic time that divides eons into smaller units of time. ► Only the Phanerozoic eon is divided into eras. ► Examples: Paleozoic, Mesozoic, and Cenozoic eras

Periods period a unit of geologic time that divides eras into smaller units of time. ► Eras are divided into shorter time units called periods. Each period is characterized by specific fossils. ► Example periods: Devonian, Jurassic, Quaternary periods.

Epochs epoch a subdivision of geologic time that divides periods into smaller units of time. ► Where the rock record is most complete, a detailed fossil record may allow scientists to divide periods into shorter time units called epochs. ► Examples: Paleocene, Pleistocene, Holocene epochs.

Essential Question: Identify the Characteristics of Precambrian Rock and what has been learned of life in the Paleozoic era, Mesozoic era and Cenozoic era 18.2 Geologic History

Evolution evolution an inheritable change in the characteristics within a population from one generation to the next; the development of new types of organisms from preexisting types of organisms over time. ► By examining rock layers and fossils, scientists have discovered evidence that species of living things have changed over time. ► Scientists call this process evolution.

Evolution and Geologic Change ► Scientists think that evolution occurs by means of natural selection. Evidence for evolution included the similarity in skeletal structures of animals. ► Major geologic and climatic changes can affect the ability of some organisms to survive. ► By using geologic evidence, scientists try to determine how environmental changes affected organisms in the past.

Evolution

Precambrian Rocks ► Precambrian time is from 4.6 billion years ago to about 540 million years ago, stared when the Earth’s crust cooled enough for rocks to form. ► The rock material has been completely changed by the process of plate tectonics and metamorphism ► Exposed Precambrian rock is call a shield and can be found on every continent, half of all valuable minerals are here. (gold, iron, nickel, and copper)

Precambrian Rocks ► Fossil are a rare find, the most common is a Stromatolites, which formed from cynobateria ► This implies shallow seas, the imprints of worms, jellyfish, and one celled organisms have been found late in Precambrian rocks

The Paleozoic Era ► Started 540 million years ago and ended 248 million years ago ► The continents came together during this time and there was abundant life in the oceans and on land ► This era has been divided into seven periods: Cambrian, Ordovician, Silurian, Devonian, Carboniferous and Permian

The Cambrian period ► During this period there was an explosion of marine life, trilobites been one of there marker index fossils used to date the different periods. ► Brachiopods also formed during this time and still exist today ► The fossil record is rich because animals developed hard shells during this period. ► There is no evidence of life on land in this period

The Ordovician Period ► More brachiopods developed and the trilobites began to decline, snail clams and other mollusk became the dominate life forms ► The first fish with a vertebrate developed in this period, no jaws or teeth and it had bony plates ► Still no life on land

The Silurian Period ► During this time both invertebrate and vertebrate creatures thrived ► Echinoderms (sea stars) and corals became more numerous, as well as eurypterids ( a scorpion like creature) that reach 2.7 m in length. ► Early plant life formed and spiders and millipedes evolved

The Devonian Period ► This is the age of fish, a population explosion of fish caused adaptations like air breathing fish or lung fish ► Amphibians probably evolved from these fish ► Land plants, giant horsetails, ferns and cone bearing plants

The Carboniferous Period ► This is the period, it is believed, that coal and oil formed ► It is also a time when it was warmer and more humid world wide, swamps and forest covered most of the land ► Insects dominated the land and at the end of the period the first lizards evolved

The Permian Period ► Was the first mass extinction, many marine life disappeared forever ► The land joined together to form Pangaea ► Reptiles flourished in this new environment

The Mesozoic Era ► 248 million years ago to 65 million years ago ► The planet was warm and humid ► Pangaea broke apart, tectonic plates collide and formed new mountain ranges ► Reptiles like lizards, turtles, crocodiles, snakes and dinosaurs … the age of reptiles ► Broken into three periods; Triassic, Jurassic, and cretaceous

The Triassic Period ► Dinosaurs first appeared, some as small as a squirrel and others up to 30 m ► most about 4 to 5 meters, could move quickly ► The land was covered with cone bearing trees and palms ► The even inhabited the oceans ► Mammals first appeared in the forest and about the size of a rodent

The Jurassic Period ► Dinosaurs dominated, two types saurischians (lizard hip) and ornithischians (bird hip) ► Lizard hip included herbivores and carnivores, the largest was Apatosaurus at 25 meters and 50 tons ► The stegosaurs was part of the bird hip ► Pterosaurs was a flying dinosaur and the first feather bird appeared at this time.

The Cretaceous Period ► Dinosaurs still ruled the world with a great variety of creatures and T-Rex as the apex predator ► Plant life also evolved into angiosperm, which means they flower and fruit ► A mass extinction ended this period, no dinosaur fossils found after this period

Mass Extinctions

The Cenozoic Era ► 65 million years ago to the present ► Continents close to current positions, tectonic activity increased forming the Alps and Himalayas ► Major climate change, mammals become dominate life on the planet. ► Two periods; tertiary and quaternary ► Seven epochs; paleocene, eocene, oligocene, miocene, pliocene (tertiary), pleistocene and holocene (quaternary)

Paleocene and Eocene ► Mammal evolution took off ► The first primates evolved, lemurs ► The worldwide temperature dropped 4 degrees celsius

Oligocene and Miocene ► The large mammals developed in this time as the planet grows colder ► Sea levels dropped and the polar ice caps formed ► Deer, horses, camels, cats, dogs, raccoons, wolves, pigs and saber tooth cat

Pliocene ► Fully evolved dogs, cats, bears and horse appeared in this epoch ► The ice age started and land bridges between the continents formed allowing the animals to travel

Pleistocene and Holocene ► There where several ice ages in this time, with some animals developing thick fur or migrating to warmer climates and some went extinct altogether ► Humans first appeared as hunters ► The Holocene started 11,000 years ago with the end of the ice age, Homo sapiens developed agriculture and use tools made from metals