1. A View of Earth’s Past Earth and Space Science Austin High School 2015-2016

2. Geological Time Earth’s surface is constantly changing As conditions change, organisms flourish an than later become extinct Evidence of change is recorded in the rock layers of earth’s crust To describe the sequence and length of change, scientist have developed a geologic time scale The scale outlines the development of earth ad life on earth

3. The Geological Column Applying the principle that old layers of rock are below young layers scientist determine the relative ages of sedimentary rock in different areas around the world No single area on earth contain a record of all geologic time, scientist combined their observations to create a standard arrangement of rock layers

4. The Geological Column Ordered arrangement of rock layers is called a geologic column Geologic column represent a timeline of the earth’s history Oldest rock at the bottom of the column Columns are distinguished by the rock type and kinds of fossils the layers contain Fossils in upper layers layers resemble modern plants/animals, where lower (older) layers fossils differ from those living today The fossils discovered in old layers are from species that have been extinct for millions of years.

6. Using a Geologic Column Geological columns were first developed using factors such as average rates of sediment deposition to estimate the age of rock layers Development of radiometric dating (ex. Carbon dating) to determine the absolute ages of rock layers with more accuracy Geologic columns can now be used to estimate the age of rock that cannot be dated radiometrically A comparison between a given rock layer and a similar layer in a geologic column (contains same fossils or same relative position) can be used to determine age

7. Division of Geologic Time Geological history of earth is marked by major change in earth’s surface, climate, and types of organisms Geologist use these indicators to divided the geologic time scale into smaller units Geological time is generally characterized by fossils of a dominant life-form. Scientist commonly use abbreviations when they discuss geologic time (so long)  Ma = mega annum, which means “one million years”

8. Eons and Eras Largest unit of geologic time is an eon Geologic time is divided into four eons The Hadean eon The Archean eon The Proterozoic Eon The Phanerozoic Eon The first three eons are part of a time internal commonly known as Precambrian time Precambrian is a 4 billion year interval that contains most of earth’s history Very few fossils exist in early Precambrian rocks, so dividing Precambrian time into smaller time units is difficult Precambrian

9. Eons and Eras After Precambrian time the Phanerozoic eon began This eon is divided into smaller units of geologic time called eras The first era of the Phanerozic eon was the Paleozoic Era which lasted 291 millions years Paleozoic rocks contain fossils of wide variety of marine and terrestrial life forms The Mesozoic Era Began after and lasted 186 million years Mesozoic fossils include early forms of birds and reptiles The present geologic era is the Cenozoic Era which began 65 million years ago. Fossils of mammals are common in Cenozoic Rocks

10. Period and Epochs Eras are divided into shorter time units called periods Each period is characterized by specific fossils and are usually named for the location in which the fossils were first discovered Where rock records are most complete and least deformed, ad detailed fossils record may allow scientist to divide periods into shorter time units called epochs Epoch may be divided into smaller units of time called ages which are defined by the occurrence of distinct fossils in the fossil records

11. Evolution Fossils indicate the kinds of organisms that lived when rock formed By examining rock layers and fossils scientist have discovered evidence that species of living things have changed overtime, process called evolution Evolution is the gradual development of new organisms from preexisting organisms Evidence for evolution includes the similarity in skeletal structures of animals Theory of evolution by natural selection was proposed by 1859 by Charles Darwin

12. Evolution and Geologic Change Geologic and climate change can affect the ability of some organisms to survive Using geologic evidence, scientists try to determine how environmental changes affected organisms in the past Fossils records show that some organisms survived environmental changes while other organisms disappeared Fossils are used to learn why some organisms survived long periods of time without changing while other organisms changed or became extinct

13. Precambrian Time

14. Earth was formed about 4.6 billion ears ago as a large cloud or nebula spun around the newly formed sun Material spun around the sun, particles of matter began to clump together and eventually formed earth and the other planets of the solar systems The time interval that began with the formation of Earth and ended about 542 million years ago called known as Precambrian time. This division of geologic time makes up about 88% of Earth’s history Relatively little is known about what happened during this time Information is lacking because rock record is difficult to interpret Precambrian are so severely deformed and altered by tectonic activity that the original order of the rock layer is rarely identifiable

15. Precambrian Rocks Large areas of exposed Precambrian rocks, called shields exist on every continent Shields are a result of several hundred millions years of volcanic activity, mountain building, sedimentation, and metamorphism Precambrian shield were lifted and exposed at earth’s surface Half of the valuable minerals deposits in the world occur in rocks of Precambrian shields Valuable minerals include nickel, iron, gold, and copper

16. Precambrian Life Fossils are rare in Precambrian rocks because life-forms lack bones, shells, or other hard parts that commonly form fossils Precambrian rocks are old, nearly 3.9 billion years Volcanic activity, erosion, and extensive crustal movements probably destroyed most of the fossils that may have formed The most common Precambrian fossil are Stromatolites Stromatolites are reef like deposits formed by blue-green algae Stromatolites indicate tha shallow seas covered much of Earth during periods in Precambrian time Imprints of worms, jellyfish, and single-celled organisms have also been discovered from late Precambrian time

17. The Paleozoic Era Cambrian Period Ordovician Period Silurian Period Devonian Period Carboniferous Period Permian Period

18. The Paleozoic Era Geological Era that began 542 million years ago and ended about 251 million years ago At the beginning of this era, Earth’s landmasses were scattered around the world By the end, landmasses had collided to form the super- continent Pangaea Tectonic activity created new mountain ranges and lifted large area of land above sea level Paleozoic rocks hold an abundant fossils records # of plant and animal species on earth increased dramatically at the beginning of this Era

19. The Cambrain Period Variety of marine life-form appeared during this periods life-forms were more advanced than previous life-forms and quickly displaced the primitive organisms as the dominant life-forms Marine invertebrates, animals that do not have backbones, thrived in the warm waters Most common invertebrates were trilobites 2 nd most common animal, brachiopods, a group of shelled animals Other common Cambrian invertebrates included worms, jellyfish, snails, and sponges No evidence of land-dwelling plants or animals discovered

20. The Ordovician Period During this period trilobites began to shrink Clamlike, Brachiopods and cephalopods became dominant invertebrates life-forms Large # of corals appeared Vertebrates, animals that have backbones, had appeared Most primitive vertebrates were fish Ordovician fish did not have jaw or teeth and their bodies were covered with thick, bony plates No plant life on land

21. The Silurian Period Vertebrate and invertebrate marine life continued to thrive Echinoderm (relatives to modern sea stars) and corals became more common Eurypterids, Scorpion-like sea creatures existed during this period Fossils of giant of these creatures nearly 3 meters long were discovered in western New York Near the end of period, earliest plant and animals evolved on land

22. The Devonian Period Called the Age of Fishes Many fossils of bony fishes were discovered in rocks Lungfish, were fish that has the ability to breathe air Fist amphibians evolved, resembled huge salamanders During this periods, land plants began to develop In the sea, brachiopods and mollusk continued to thrive

23. The Carboniferous Period Climate was generally warm and high humidity Forest and swamps covered much land Amphibians and fish continued to flourish Insects, giant cockroaches and dragonflies were common This period is divided into two periods: Mississippian and Pennsylvanian Vertebrates that were adapted to life on land appeared, these early reptiles resembled large lizards

24. The Permian Period Permian period marks end of Paleozoic Era A mass extinction of large number of Paleozoic life-forms occurred Collision of tectonic plates created the Appalachian Mountains Shallow inland seas that had covered much of earth disappeared As sea retreated, many species of marine invertebrates became extinct Reptiles and amphibians survived the environmental changes and dominated Earth in the million years that followed End of Permian, 90% of marine organism and more than 70% of land organisms died

25. Mesozoic Era

26. The Mesozoic Era Geological era began about 251 million years ago and ended about 65 million years ago Earth’s surface changed dramatically, Pangaea broke into smaller continents and tectonic plated drifted and collided Collision uplifted mountain ranges such as the Sierra Nevada in California and Andes in South America Shallow seas and marshes covered much of the land Climate was warm and humid Lizards, turtles, crocodiles, snakes, and variety of dinosaurs flourished Also known as the “Age of Reptiles” This Era has rich fossil records and is divided into three periods

27. The Triassic Period Dinosaurs appeared during this period Some dinosaurs were the size of squirrels and some weighed as much as 15 tons Forest were lush with cone-bearing trees and cycads which are plants that resemble the palm trees of today Reptiles called ichthyosaurs lived in the Triassic oceans During this time the first mammals, small rodent-like forest dwellers appeared

28. The Jurassic Period Dinosaurs became the dominant life-form Fossils indicate two major groups of dinosaurs evolved Saurischians = “lizard-hipped” Included herbivores (plant eaters) and carnivores (meat eaters) Ornithischians = “bird-hipped” Flying reptiles called pterosaurs were common during this period

29. The Cretaceous Period Dinosaurs continued to dominate Tyrannosaurus rex existed during this time Other dinsosaur included ankylosaurs, ceratopsians, hadrossaurs Plant life become very sophisticated Earliest flowering plants or angiosperms appeared Most common of these plants included trees (magnolias and willows), Dinosaurs became extinct

30. The Cenozoic Era

31. Division of time that began 65 million years ago and includes the present time Continents moved to their present-day positions Plated collided to form Alps and Himalayas Mountain ranges Dramatic change in climate occurred Mammals became the dominant life-form and underwent many changes “Age of the Mammals”

32. Cenozoic Era Divided into 2 periods: Tertiary period - First primates appear and flowering plants become the most common. Quaternary period - Humans evolve and large mammals like woolly mammoths become extinct.

33. The End