GEOLOGIC TIMELINE

Paleozoic Era (~540 - 330 MYA)

Cambrian

Cambrian Explosion

When most of the major animal groups started to appear in the fossil record, a time of rapid expansion of diverse forms of life on Earth

All existent phyla develop

Rocks of Cambrian

Distributed in the Great Basin of the western U.S, parts of Wales, Scandinavia, and the Baltic region, Siberia and China, among other places

Rodinia

Super-continent Rodinia begins to break into smaller continents (with no correspondence to modern-day land masses)

Position of the continents was very different from current day (e.g. Califronia on the equator or Venezuela near the South Pole)

Extinction of trilobites nautiloids

50% of all animal families went extinct

Most likely due to glaciation

Ordovician

Gondwana

The area north of the tropics almost entirely ocean

Most of the world’s land collected into this southern super-continent

First Land Plants

First Coral Reefs

Geographical Changes

High sea levels at first

Global cooling, glaciation, and lots of volcanism

North America under shallow seas

Silurian

First Jawed Fish

First Vascular Plants

These plants have water-conducting tissue compared with non-vascular plants

Stabilization of the Earth’s general climate

Led to the melting of large glacial formations

This ended the previous pattern of erratic climatic fluctuations

Contributed to a substantial rise in the levels of major seas

Devonian

Ferns

First Amphibians

First Shark, Bony Fish, and Ammonoids

First Insects

i.e. Springtails

Mass Extinction

Wiped out 30% of all animal families

Most likely due to glaciation or meteorite impact

Carboniferous

Winged Insects

i.e. appearance of mayflies and cockroaches

Amniote Egg

This allowed the ancestors of birds, mammals, and reptiles to reproduce on land by preventing the dessication of the embryo inside

Mild Temperatures

Evidenced by the decrease in lycopods and large insects

Increase in the number of tree ferns

Formation of the Appalachian Mountain Belt

Collision of Laurrussia (present-day Europe and North America) into Godwanland (present-day Africa and South America)

Formation of the Ural

A collision of Siberia and eastern Europe

Permian

The Age of Amphibians

Amphibians and reptiles dominated

Largest mass extinction

Extinction of:

95% of all marine species

Trilobites

50% of all animal families

Many trees

Possibly caused by glaciation or volcanism

Pangea

Motion of the Earth’s crustal plates fused much of the total land into Pangea

Rest of the surface area of the Earth was occupied by a single ocean (Panthalassa) and a smaller sea known as Tethys

Mesozoic Era (~248 - 65 MYA)

Triassic

Start of the Age of Dinosaurs

After the largest extinction event in history (Permian Extinction), the survivors of that event spread and recolonized

First Mammals and Crocodyliformes

Some scientists believe that mammals evolved from a group of extinct mammal-like reptiles, Theriodontia

Minor extinction

35% of all animal families died out

This allowed for dinosaurs to expand into many niches

It is not certain what caused this extinction, possibly global cooling or an asteroid impact

In the seas, icthyosaurs (marine reptiles) appeared

Jurassic

Earthworms

More dinosaur species appear

i.e. The giant Sauropod

The Dipolodocus and Apatosaurus diversified

Minor mass extinction at the end of the early Jurassic period

more than 80% of marine bivalve species (i.e. clams) and other shallow-water specieis died out

Possibly triggered by the release of huge methane deposits from within the Earth

Appearance of dinosaur-like birds

Archaepteryx were the first, primitive, dinosaur-like birds

Pterosaurs were the largest vertebrates ever known to fly

Cretaceous

First Flowering Plants

i.e. Angiosperms (evolved from a specialized group of seed ferns)

Quickly dominated plant life on land and remain so today

The K-T Extinction of Dinosaurs

Most likely caused by asteroid impact or volcanism

Continents take on a Modern-Day Look

The Uplift of the Rocky Mountains

Giant blocks of ancient crystalline rock, overlain by younger sedimentary broke and were thrust upward

Streams eroded away at the sedimentary rock

Cenozoic Era (~65 MYA - Today)

Paleocene

First large mammals

At the start of the Paleocene Epoch, the world was practically without larger terrestrial animals, however, by the end, they had occupied a large part of the vacant ecological niches.

Paleocene mammals show the beginning of specializations that characterize their later descendants

First primitive primates

Eocene

Eohippus - First Known Horse

The Circum-Antarctic Current

Caused by the separation of Antartica and Australia creating a deep water passage between those two continents

This changed oceanic circulation patterns and global heat transport, resulting in a global cooling event

Primitive whales appear

Oligocene

Appearance of new mammals

i.e. pigs, deer, cats, rhinos, tapirs

Appearance of many grasses

intimately linked to the expansion of grazing animals

The Grand Coupure

event involved the immigration from areas to the east of many taxa, artiodactyls, and perissodactyls

The extinction of any Eocene genera and species

around 17 generic extinctions

about 20 first appearances

Miocene

Two new major ecosystems

Kelp forests

Led to the appearance of sea otters and other critters unique to this environment

Grasslands

The expansion of grasslands correlated to a drying of continental interiors as the global warming first warmed, then cooled

Led to open habitat herbivores and carnivores

Formation of the Sierra Nevada and Cascade Mountain Ranges

Caused a non-seasonal and drier mid-continent climate

Increase of droughts and decrease in rainfall promoted drier climates

Appearance of More Mammals

i.e. Horses, dogs, bears

Rise of the Andes Mountains

This event was caused by the movements in plate tectonics in the vicinity of South America

This led to the formation of a rain shadow effect in the southeastern part of the continent

Pliocene

First hominids

Enormous spread of grasslands and savannas

possibly caused by the cooling and drying of global environments

change in vegetation led to the rise of grazers in these areas

grazers got larger and developed larger teeth suitable for a diet of grass

longer legs allowed for them to walk long distances to new feeding grounds

Formation of the Himalayan Mountains

tectonic plates of India and Asia collided

Drying of the Mediterranean Sea

remained plains and grasslands for the next several million years

Pleistocene

Little Ice Age

mountain glaciers formed on all continents

much of the world's temperate zones were alternately covered by glaciers during cool periods and uncovered during warmer interglacial periods

Evolution of Homo Sapiens

Mass extinction of large mammals and many birds

Likely caused by the end of the last ice age

Holocene (Today)

Human Civilization

The Holocene witnessed all of humanity’s recorded history

Global Warming

Human activity influencing the surrounding environment

Habitat destruction, pollution, etc. causing mass extinction of plant and animal species

Predicted that 20% of all plant and animal species on Earth will be extinct in the next 25 years

Industrial Revolution

Led to a new age of innovation and technology

Introduced concepts of factories, AI, machine learning, robotics, that could possibly reduce the need for much human labour in the near future