Earth’s Past

The Geologic Time Scale Earth’s history is divided different sections of time The sections are determined by the living things and the rock record The geologic time scale is broken up into eons, eras, periods, and sometimes epochs

Epochs – Divide periods Periods – Divide eras Eras – Divide eons Eons – Longest segment of geologic time

Changes Earth has changed dramatically over time Earth atmosphere initially comprised of CO2, Sulfur Dioxide, Water Vapor, and Nitrogen Liquid Oceans Developed Oxygen (O2) entered the atmosphere with the appearance of photosynthetic organisms, such as algae Living things have evolved and mass extinctions have occurred

Evolution Since appearing on Earth, animals and plants have been changing in appearance, size, and structure This change is called evolution. In the 1800’s, Charles Darwin called the process of the species that survive due to traits better suited to the environment natural selection

The Precambrian (4.5-543 mya) Precambrian time includes all geologic time before the Cambrian period in the Paleozoic era. This is the combination of the Hadean Archean Proterozoic

The Precambrian Hadean●Archean●Proterozoic Hadean Eon The Formation of Earth Meteor Impacts No Life Volcanic Activity Formation of Early Atmosphere Cooling of Water Vapor to Form Oceans

The Precambrian Hadean●Archean●Proterozoic Archean Eon (3.8-2.5 bya) Started with the formation of the crust and first rocks (3.8 bya) The Cratons are the oldest Archean

The Precambrian Hadean●Archean●Proterozoic The first evidence of life is found in Archean rocks Simple bacteria (3.8 bya) Cyanobacteria – simple single celled organisms (3.5 bya) Trapped in sediment they form structures called stromatolites Photosynthesis began ~3 bya

The Precambrian Hadean●Archean●Proterozoic Proterozoic Eon (2.5 bya -543 mya) Abundant volcanic activity No life on land All organisms had soft bodies Multicellular life began (2.1 bya) Taxa such as jellyfish and worms appear at the end of the Proterozoic (1 bya)

Paleozoic Era (543-290 mya) This era is the beginning of an abundant fossil record It is broken up into six periods Cambrian Ordovician Silurian Devonian Carboniferous Permian

Paleozoic Cambrian●Ordovician●Silurian●Devonian● Carboniferous●Permian Cambrian Period (543-490mya) The most commonly preserved Cambrian animal is the trilobite, a crablike invertebrate. Very little mountain building Warm oceans All life in water Cambrian Explosion Hard Shells evolved leaving a better fossil record

Paleozoic Cambrian●Ordovician●Silurian●Devonian● Carboniferous●Permian Ordovician Period (490-443mya) The graptolite is a useful index fossil of the Ordovician. Appalachian Mountains formed as tectonic plates crashed into one another All life in water

Paleozoic Cambrian●Ordovician●Silurian●Devonian● Carboniferous●Permian Silurian Period (443-417 mya) The eurypterid is sometimes called a sea scorpion is a good index fossil . Evolution of terrestrial (land) The first land animals included distant relatives of spiders, millipedes, and scorpions.

The geologic time scale is broken up into… Centuries, scores, decades, years, and months Eons, eras, periods, and sometimes epochs Units Pounds and ounces

Which statement is true? An epoch is bigger than a period An era is bigger than an eon An epoch is bigger than an eon An era is bigger than a period

What gave the earth the great majority of its oxygen in the atmosphere? Aliens Pollution Plants like algae Comets It was there in the first place

What is evolution? Mass extinction of plants and/or animals Plants/animals changing and adapting to better suit their environment A time period An awesome band name \m/

What is the oldest time period in Earth’s history? Proterozoic Archean Hadean Jurassic Cretaceous

When was the first evidence of life found? Proterozoic Archean Hadean Jurassic Cretaceous Silurian

When was the first evidence of life on land found? Proterozoic Archean Hadean Jurassic Cretaceous Silurian

Paleozoic Cambrian●Ordovician●Silurian●Devonian● Carboniferous●Permian Devonian Period (417-354 mya) “Age of the Fish” Lung fish first appeared (ancestor to amphibians) First appearance of forests consisting of ferns, giant rushes, and primitive conifers.

Paleozoic Cambrian●Ordovician●Silurian●Devonian● Carboniferous●Permian Carboniferous Period AKA: Mississippian and Pennsylvanian Periods Mississippian Period: Crinoids, which look like plants, are actually invertebrate animals related to sea stars. Foraminifera are one-celled organisms with tiny calcite shells.

Paleozoic Cambrian●Ordovician●Silurian●Devonian● Carboniferous●Permian Pennsylvanian Period First appearance of reptiles, the first true land vertebrates (with backbone) Large insects including early ancestors of the cockroach

Paleozoic Cambrian●Ordovician●Silurian●Devonian● Carboniferous●Permian Permian Period Dry climate Widespread mountain building caused by continental collisions Mass extinction ended the period and the Paleozoic Era Marine cephalopods and reptiles were among the survivors

Mesozoic Era (248-65 mya) The Mesozoic Era “Age of the Reptiles” Triassic Period Jurassic Period Cretaceous Period

Mesozoic Triassic●Jurassic●Cretaceous Triassic Period (248-206 mya) Dinosaurs made their first appearance on land. Some of the first dinosaurs were about the size of a cat. Cephalopods called ammonites are an important index fossil. During most of the Triassic, almost all of Earth’s land was joined as the supercontinent Pangaea.

Mesozoic Triassic●Jurassic●Cretaceous Jurassic Period Many larger dinosaurs, including brachiosaurus and Allosaurus Morphing insects like flies and caterpillars appeared First birds appeared

Mesozoic Triassic●Jurassic●Cretaceous Cretaceous Period The largest dinosaurs lived during this period, often exceeding 25 meters in length. (T-rex, Brachiosaurs) The appearance of flowering plants is perhaps the greatest event. Modern trees developed. Ex. oak, maple, birch.

Mesozoic Triassic●Jurassic●Cretaceous Continents appeared much as they do today. Evidence supports asteroid collision caused mass extinction at end of period This ended the Mesozoic Era (183 million years of dinosaur domination) Mammals survived the mass extinction

Cenozoic Era (65 mya -present) Regarded as Earth’s recent history “The Age of the Mammals” Divided into three periods: Paleogene Neogene Quaternary

Cenozoic Paleogene●Neogene●Quaternary Paleogene Period Modern Mountain Ranges:Rockies, the Alps, Himalayas, Introduction of mammals Global climate cooled

Cenozoic Paleogene●Neogene●Quaternary Neogene Period Appearance of grasses lead to explosion of grazing animals such as sheep and cows Modern forms of the horse, camel, and elephant debuted here

Cenozoic Paleogene●Neogene●Quaternary Quaternary Period Great temperature fluctuations from warm to cold, leading to increased rates of extinction and evolution First appearance of humans

What period did crinoids appear? Cambrian Ordovician Silurian Devonian Carboniferous Permian

What period did reptiles first appear? Cambrian Ordovician Silurian Devonian Carboniferous Permian

What period did forests appear on land? Cambrian Ordovician Silurian Devonian Carboniferous Permian

What was the Mesozoic Era most known for? First appearance of life First appearance of oxygen in the atmosphere First appearance of land dinosaurs First appearance of humans

Which period saw the largest dinosaurs? Cambrian Ordovician Silurian Triassic Jurassic Cretaceous Hadean Mississippian

What period did mammals first appear? Paleogene Neogene Quaternary Triassic Jurassic Cretaceous Hadean Mississippian

What period did humans first appear? Paleogene Neogene Quaternary Triassic Jurassic Cretaceous Hadean Mississippian