Exploring Geological Time

 

An INteractive Chart

Geological time spans from the formation of the earth to the modern day, measured in the billions of years. These huge amounts of time can be difficult to grasp when we are used to measuring in terms of human lifetimes! On the chart below, the last 100 years of our history would be represented by a thin slice 1/50th of a pixel thick! We have even had to use two scales to fit this chart on the screen, with everything before the Paleozoic being measured in billions of years, and not millions. 

Explore this chart by hovering over the icons to reveal stories about our rich geological past!

 

Key

Global Event  Rock Forming    In the Ocean  Plants  Animals

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Formation of the Earth

4.6 Billion Years Ago

The Earth forms from a cloud of rocks, dust and ice drifting around an early Sun.

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First Liquid Water

4.4 Billion Years Ago

The surface of the Earth had cooled enough to allow rocks to form, and the first pools of liquid water to condense

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Oldest Rock in Canada

4.03 Billion Years Ago

The Acasta Gneiss is a tonalite gneiss in the Slave craton in Northwest Territories, Canada. The rock body is exposed on an island about 300 kilometres north of Yellowknife.

The rock of the outcrop was metamorphosed 3.58 to 4.031 billion years ago and is the oldest known intact crustal fragment on Earth

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First Fossil Evidence of Life

3.5 Billion Years Ago

The first (undisputed) life appeared on earth 3.5 Billion Years ago, and are found in the Australian "Apex Cherts". These are fossilized remains of bacteria that forms 'mats of material around submarine volcanic vents. 

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Banded Iron Formations

3.0 Billion Years Ago

The formations first appear 3.0 billion years ago, and become abundant around the time of the great oxygenation event, 2,400 million years ago (mya or Ma), and become less common after 1,800 mya with evidence pointing to intermittent low levels of free atmospheric oxygen. 750 million years ago new banded iron formations formed that may be associated with the theoretical Snowball Earth.

The conventional hypothesis is that the banded iron layers were formed in sea water as the result of oxygen released by photosynthetic cyanobacteria. The oxygen then combined with dissolved iron in Earth's oceans to form insoluble iron oxides, which precipitated out, forming a thin layer on the ocean floor, which may have been anoxic mud (forming shale and chert). Each band is similar to a varve, to the extent that the banding is assumed to result from cyclic variations in available oxygen. It is unclear whether these banded ironstone formations were seasonal, followed some feedback oscillation in the ocean's complex system or followed some other cycle. It is assumed that initially the Earth started with vast amounts of iron and nickel dissolved in the world's acidic seas. As photosynthetic organisms generated oxygen, the available iron in the Earth's oceans precipitated out as iron oxides. At a suspected tipping point where the oceans became permanently oxygenated, small variations in oxygen production produced periods of free oxygen in the surface waters, alternating with periods of iron oxide deposition.

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First Plate Tectonics

3.2 Billion Years Ago

Around 3.2 Billion Years Ago, the first evidence for plate tectonics has been noted from rocks preserved in Greenland. The composition of the rocks on the surface began to change and incorporate water, which allowed some areas to sink, melt and be recycled in processes that we are familiar with today.

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Atmospheric Oxygen

2.3 Billion Years Ago

Cyanobacteria or blue-green algae became the first microbes to produce oxygen by photosynthesis, perhaps as long ago as 3.5 billion years ago and certainly by 2.7 billion years ago. But, mysteriously, there was a long lag time – hundreds of millions of years – before Earth’s atmosphere first gained significant amounts oxygen, some 2.4 billion to 2.3 billion years ago.

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First Complex Cells

1.2 Billion Years Ago

The first multicelled organisms are believed to have been red algae, which appeared sometime between 1.4 and 1.2 billion years ago. This was about two billion years after stromatolites first appeared. Thus, more than one-half the time life has been present on earth, it was occupied by only single cell organisms.

Ancient micro-fossils of red algae were preserved and have been found on Somerset Island in northern arctic Canada. These fossils are as old as 1.2 billion years. The first multicellular organisms had certain characteristics that have defined all complex life forms since. Red algae invented sex and reproduced sexually.

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Cambrian Explosion

543 Million Years Ago

The climate at the beginning of the Cambrian Period (from 543 to 490 million years ago), was cold but as the period time passed, the climate all over the earth grew warmer. The continents were still forming and were mostly barren rocks. The land had no plant or animal life on it yet. This made the seas the preferred place for species to live. Sea levels flooded many low land masses and created shallow habitats ideal for spawning new marine life-forms.

The Cambrian Explosion lasted about 53 million years and brought about a dramatic burst of evolutionary changes in new life. Among the creatures that evolved during this period were hard-bodied clams and the ancestors of spiders and insects

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Burgess Shale

508 Million Years Ago

The Burgess Shale is a fossil-bearing deposit exposed in the Canadian Rockies of British Columbia, Canada. It is famous for the exceptional preservation of the soft parts of its fossils. At 508 million years old (middle Cambrian), it is one of the earliest fossil beds containing soft-part imprints.

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First Land Plants

450 Million Years Ago

The first plants needed a source of water for photosynthesis, so they were found on marsh land where they could easily obtain water from the damp soil. Because they did not have any tissue that conducted water very well, they had to stay close to a supply in order to obtain the water they needed for photosynthesis.

One of the major steps in plant evolution was the widespread evolution of spores as a form of plant reproduction. Spores are unicell organisms that are mobile and can reproduce forming new plants. Because spores could migrate by wind from place to place, they allowed plants to spread across the land. Spores eventually evolved into seeds, which are the multi-cell reproduction organisms of most of our current day plants.

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First Coral Reefs

485 Million Years Ago

During the early Ordovician, the first true coral reefs formed in shallow, sunlit waters. Sea levels were extremely high during this period which allowed for flooding of coastal regions, forming perfect reef building conditions.

Although reefs existed in the Cambrian, these were formed of algae. Now corals had evolved and became the primary reef building organism. Ordovician reefs supported huge ecosystems of animals and drove evolution and biodiversity.

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First Animals on Land

450 Million Years Ago

Arthropods (i.e. insects, scorpions) provide the earliest identifiable fossils of land animals, from about 419 million years ago in the Late Silurian, and terrestrial tracks from about 450 million years ago appear to have been made by arthropods. Arthropods were well pre-adapted to colonize land, because their existing jointed exoskeletons provided protection against desiccation, support against gravity and a means of locomotion that was not dependent on water. Around the same time the aquatic, scorpion-like eurypterids became the largest ever arthropods, some as long as 2.5 metres (8.2 ft).

The oldest known spider-ancestor is the from about 420 million years ago in the Silurian period

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First Tetrapods on Land

397 Million Years Ago

Tetrapods are four-limbed animals, including humans! These first evolved from fish that were coming on to land to hunt the wealth of insects that had evolved. Early tetrapods would have been amphibious, similar to modern salamanders. Fossils become more common around 380 million years ago, but trackways from Poland were found to be 397 million years old and have recently pushed back these timelines.

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First Trees

390 Million Years Ago

The first trees would have looked totally alien to us today. They would have had bulbous trunks, strap-like roots and leafless branches that would have photosynthesized. Fossils have been found that they grew up to 8m high and grew along marshy wet rivers. 

The first true trees evolved from these around 10 million years later, and had tough, woody trunks topped with a crown of fern-like leaves. 

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Reptiles Appear

298 Million Years Ago

The first reptiles appeared around 315 million years ago, although became more common around 300 million years. Reptiles evolved from amphibians and lost their dependence on water, especially developing hard-shelled eggs that replaced the gelatinous ones amphibians would deposit in water. 

A group of reptiles, called "synapsids", appeared soon after. This was the branch on the tree of life that eventually evolved into mammals, including humans, 

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First True Dinosaurs

228 Million Years Ago

The first true dinosaurs appeared between 231 and 228 million years ago during the Late Triassic. 

Eoraptor was one of these first dinosaurs, and is found in modern day Argentina. It has a slender body and grew to about one meter in length. It ran on two legs and would have hunted smaller reptiles, amphibians and insects as well as eating plants. 

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Mammals Appear

210 Million Years Ago

The first mammals were small and shrew-like, likely nocturnal and would have hunted insects as well as eating plants. It is presumed that the earliest types, including Morganucodon, lived in burrows which they filled with plant material to make nests. 

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Liopleurodon Hunts The Oceans

165 Million Years Ago

Liopluerodon was a large, carnivorous marine reptile that was a type of "short-necked" plesiosaur. It was the top predator of its time and swam in the shallow seas that covered Europe during the Jurassic. They could grow up to to 10 meters in length and would have eaten other plesiosurs, icthyosaurs and even giant squid and ammonites!

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Stegosaurs Roam the Land

155 Million Years Ago

Stegosaurs were one of the iconic dinosaurs we know and love! They were large herbivores that lived during the Jurassic and are instantly recognizable for the line of plates along their backs. 

They belonged to a family called "stegosauridae" who were found all over the world, including North America, Europe and Asia. 

Fun fact! The spikes on the tail are called the "thagomizer", a name adopted from Gary Larson's comic "The Far Side"!

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The Largest Dinosaur

95 Million Years Ago

Argentinosaurus was a type of long-necked dinosaur ("sauropod") that lived in the Late Cretaceous of Argentina. It grew to almost 40 meters in length and was thought to weigh up to 100 tonnes, making it the longest and heaviest of all the known dinosaurs. 

 

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The First Bird

150 Million Years Ago

The first undisputed bird is Archaeopteryx from the Jurassic. Their fossils are found in southern Germany from an area that would have been small island chains in a shallow tropical sea 150 million years ago.

They evolved from small, two legged predatory dinosaurs and represent a snapshot of the evolution between dinosaurs and birds. Archaeopteryx had feathers (which started to evolve on dinosaurs in the late Jurassic), but also had teeth in its mouth and claws on its wings. It was capable of flight, but scientists think it was more likely to be a glider, jumping between trees in the pursuit of prey.

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K-T Mass Extinction

66 Million Years Ago

Sixty-five million years ago, 75% of all life on Earth was wiped out. This event is known as the K-T mass extinction because it occurred at the boundary between the Cretaceous (K) and Tertiary (T) time periods. The most famous group of animals to perish was the dinosaurs, but ammonites, plesiosaurs, ichthyosaurs and pterosaurs all disappeared too. 

It is thought that several catastrophic events occurred that pushed life to the brink. The most well known is an asteroid that hit the Gulf of Mexico, but at the same time there were massive volcanic eruptions in India that formed the Deccan Traps. Both of these would have been devastating locally, but the ash and chemicals released into the atmosphere had wider effects that eventually led to the demise of three-quarters of life at the time.

 

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