History of earth

HISTORY OF EARTH

UNIT 3

1. Supernova2. Nebula3. Temperature rose

due to nuclear fusion reactions

4. Temperature fall and materials start condensing

5. Condensed fragments collided and got together until planets were formed

The origin of the Solar System

THE SOLAR SYSTEM

Absolute dating methods measure the time that has elapsed since a geologic event happened (rock formation, deposition of a stratum, the age of a fossil, etc.).

They are:SedBiological methodsimentological methodsRadiometric methods

METHODS OF ABSOLUTE DATING

Biological methods

These are based on the analysis of biological rhythms associated with intervals of time, such as the growth rings of trees or daily growth bands (striations) on living corals.

Each year, trees develop two rings: one light ring (in spring) and one dark ring (in summer). By doing a very simple calculation, we can tell the age of a tree if we count the number of rings inside the tree trunk.

Sedimentological methodsThese are based on cyclical sediment deposits, like what happens with glacial varves, which are sediments that are deposited at the bottom of glacial lakes, depending on seasonal changes.

Winter Summer

Ice

Glacial lake

Thick clear layer of sedimentsThin dark layer of sediments

Glacial varvesOnly a thin dark layer (consisting of clays and organic matter) accumulates when the surface of the lake is frozen over in winter.

A thick clear detrital layer is deposited into the lake when the ice melts in summer.

It is possible to calculate the age of the lake by counting the varves.

Radioactive elements such as uranium 238 (U238) or carbon-14 (14C) are used; they may be contained in rocks, fossils or archaeological remains.

Radiometric methods

Radioactive isotopes are unstable and emit radiation, so that after some time, they transform into other more stable atoms.

HALF LIFE OF RADIACTIVE ATOMSIf we know the rate of disintegration, we can date the age of a sample by measuring the ratio between unstable radioactive atoms and stable atoms formed from them.

METHODS OF RELATIVE DATINGRelative dating consists of ordering the strata or geological events recorded in one or more stratigraphic series chronologically, without specifying how long ago they occurred or how long they lasted.Relative dating is achieved by interpreting satratigraphic series, uisng the following basic principles:Principle of uniformitarismPrinciple of the sucession of geological eventsPrinciple of the arrengement of strata

Original horizontalityLateral continuitySuperposition

Principle of the sucession of fossils

The four steps of fossilization

1. Death

2. Burial

3. Replacement

4. Erosion

INDEX FOSSILS

CATASTROPHISM

UNIFORMITARISM

GEOLOGIC TIME SCALE

The Precambrian Era: Geological and paleoclimatic events

Hadean era (4,500-3,800 m.y.)

1. Meterorites continually collided the Earth

2. Layers were formed3. Atmosphere and oceans were formed4. The Moon was formed5. Life appeared at the end of the period

1. Meteorite bombardment stopped2. Tectonic plates movement started3. Oxygen appeared in the atmosphere4. Iron oxide appeared in rocks5. Rodinia supercontinent was formed6. The biggest glacial period started

Archaean and Proterozoic (3,800-540 m.y.)

• 542 to 500 million years ago, the continents were separated by shallow, warm seas.

• 460 to 350 million years ago, the continents began to come together. The Caledonian orogeny mountain ranges formed as a result of several continental masses colliding and glaciation occurred.

• 300 to 250 million years ago, the Variscan orogeny mountain-building event was caused by new continental collisions. The supercontinent Pangea II was formed and there was another glaciation. The climate in the inland regions of the continent was very dry as it was very far from the sea. An episode of massive volcanic activity occurred at the end of the Permian period that caused global warming due to increasing greenhouse gases in the atmosphere.

The Paleozoic Era: Geological and paleoclimatic events

• 250 to 200 million years ago, the continents came together as Pangea II. The climate was very warm and very dry in the interior of the supercontinent. At the end of the Triassic period, continental fragmentation began and shallow seas opened up.

• 200 to 145 million years ago, the opening of the continents continued. The climate was much wetter and it was still warm (tropical to humid temperate environments).

• 145 to 65 million years ago, the continents continued to separate (the Atlantic opened up), but Africa and India started colliding with Eurasia, which initiated the uplifting of the Alpine orogeny mountain building event. The climate started to cool. At the end of the Cretaceous period, global volcanic activity increased and a large asteroid struck Earth.

The Mesozoic Era: Geological and paleoclimatic events

• 65 to 23 million years ago, the separation of the continents that began in the Cretaceous period (the opening of the Atlantic) continued and India completed its collision with Eurasia. This marked the end of the Alpine orogeny. The mountains on the western boundary of America formed. The climate at this time was still subtropical and humid in almost all regions.

• 23 to 2.5 million years ago, the continents reached positions close to the ones they are in at the present time. The Red Sea and East Africa's Great Rift Valley opened. The climate became cooler and more arid.

• 2.5 to 0 million years ago, several glacial episodes occurred.

The Cenozic Era: Geological and paleoclimatic events

• 3,800 to 3,500 million years ago, the earliest life appears on Earth, probably originating in an aquatic environment. There are indications of this in the biochemical clues that appear in rocks from this time and in the first fossilised prokaryotes.

The Precambrian Era: Biological events

• 3,400 million years ago, stromatolites appear. These are structures produced by the activity of cyanobacteria. These and other photoautotroph organisms filled the atmosphere with oxygen that produced mass extinction of anaerobic organisms 2,000 million years ago.

• 700 to 542 million years ago, mass extinctions occur during glaciations and a subsequent explosion of biodiversity takes place. In the Proterozoic formations in Ediacara (Australia), fossils of beings similar to simple animals appear (some different from existing groups and others such as sponges, jellyfish and worms).

• 1,700 to 1,000 million years ago, eukaryotes and multicellular organisms emerge.

Ediacaran fauna

• 542 to 460 million years ago, there was a great explosion of marine life. The majority of invertebrate groups, including the first chordates, appeared.

The Paleozoic Era: Biological events

• 460 to 400 million years ago, fish appeared. Marine biodiversity decreased due to the glaciation at the end of the Ordovician period, but it recovered later. New groups of fish started showing up. The first plants and terrestrial arthropods emerged.

• 400 to 250 million years ago, there was a great diversity of fish. Plants without seeds, and later conifers, flourished in the terrestrial environment. The first amphibians and early reptiles started showing up. The latter proliferated and diversified, adapting better to arid conditions. At the end of the era, the greatest mass extinction in the history of the Earth occurred (90% of species were wiped out).

Life in the Paleozoic Era (540-250 m.y.)

Trilobite Armoured fish

Ferns Terrestrial animals

• 250 to 200 million years ago, fish and marine invertebrates recovered from the Permian extinction. On land, the arid climate favoured primitive gymnosperms, insects and reptiles (the latter adapted to all environments). The first dinosaurs and early mammals started showing up.

The Mesozoic Era: Biological events

• 200 to 145 million years ago, there was a great diversity of marine invertebrates. Fish and marine reptiles dominated the seas. Conifers dominated the flora and dinosaurs diversified and reached large sizes. The first birds appeared.

• 145 to 65 million years ago, there was a great diversity of marine life and dinosaurs. Flowering plants, pollinating insects and marsupials appeared. The end of the Cretaceous period saw a rapid mass extinction, especially of many sea creatures, such as the ammonites, and terrestrial creatures such as dinosaurs.

Life in the Mesozoic Era (250-65 m.y.)

Dinosaurs

Gymnosperms

Ammonite

• 65 to 23 million years ago, the survivors of the extinction in the Cretaceous period, especially angiosperm plants, mammals and birds, spread and diversified.

The Cenozoic Era: Biological events

• 2.3 to 2.5 million years ago, birds and mammals diversified widely, and in many cases, into large sizes. Many of the existing groups, including the first anthropoid primates (and hominids at end of the period), appeared. A subtropical humid forest flora dominated in almost all latitudes, although at the end of this period the shift towards a progressively cooler and drier climate modified the fauna and flora.

• 2.5 to 0 million years ago, glaciations radically altered the flora and caused the emergence of many modern groups of plants. There were new mammal species adapted to colder or drier climates. Hominids emerged and the human species appeared.

Life in the Cenozoic Era (65 m.y. – present)

Mammals & birds

HumansAngiosperms

The Precambrian Era

HADEAN EON ARCHEAN EON PROTEROZOIC EON4 000mya

2 500 mya542mya

2500 mya. There are already continental masses with sedimentary rock

3500 mya. The oceans have already

formed

4650 mya. Origin of the Earth's crust

700 to 580 mya. Global glaciation occurs

650 mya. The first great supercontinent known as

Pangea I is formed

3800 mya. Possible origin of life

3500 mya. The first organisms appear which are very simple prokaryotes

3400 mya. First known cyanobacteria (blue-green algae) form stromatolites

2000 mya. The majority of non-aerobic organisms become extinct

600 mya. Mass extinction occurs due to glaciations

500 mya. "Ediacara fauna”the first animals, appear

SUMMARY

The Paleozoic Era

EON PHANEROZOIC PALEOZOIC PALEOZOIC

Cambrian Ordovician Silurian Devonian Carboniferous Permian

Fish with jaws Anomalocaris

Trilobites

250 mya. Another great supercontinent

known as Pangea II is formed.

500 mya. The continents have separated.

488 443 416 359 299

450 mya. Several continental masses come together

causing a glaciation and the Caledonian orogeny.

300 mya. The continents come together causing another glaciation and the Variscan

orogeny.

250 mya. There is massive

volcanic activity.

542 to 460 mya (million years ago). There is an explosion of marine life. 555 mya. Fish appear.

419 mya. Plants and terrestrial arthropods emerge. There is a great diversity of fish.

Pteridophytes (ferns) predominate.

360 mya. The first amphibians appear and predominate.

380 mya. Lobe-finned fish emerge; they are the ancestors of tetrapods.

250 mya. 90% of life forms become extinct.

Ichthyostega

Dimetrodon

320 mya. Reptiles appear and diversify.

Hallucigenia

SUMMARY

The Mesozoic Era

EON PHANEROZOIC MESOZOIC MESOZOIC

Jurassic Cretaceous

199 145

Ammonites

Triassic

Cynodont

Apatosaurio

Plesiosaur

Ichthyosaur

AllosaurusTriceratops

Tyrannosaurus

65 mya. Mass extinction caused by a meteorite impact occurs.

65 mya. An enormous meteorite crashes to Earth, in the Gulf of

Mexico.

210 mya. Break-up of Pangea II starts. The continents separate.

140 mya. The opening of the Atlantic starts.

70 mya. The Alpine

Orogeny starts.

250 mya. Marine life recovers from the extinction of the Permian Period. On land, gymnosperms, insects and reptiles dominate.

240 mya. There are reptiles in all environments. The first dinosaurs and early mammals start showing up.

200 mya. Gymnosperms dominate.

Pterosaur

160 mya. Birds

appear.

128 mya. Angiosperms appear.

80 mya. Dinosaurs dominate the Earth.

SUMMARY

The Cenozic Era

PHANEROZOIC EONCENOZOIC

Neogene Quaternary23

Paleogene

Arsinotherium

60 mya. Populations of mammals, birds and angiosperm plants peak.

CENOZOIC

2,5

Diatryma

Indricotherium

Proconsul Animals from the Ice Age

The continents reach their current positions.60 mya. Continental

separation continues.

25 mya. The Alpine

orogeny ends.

10 mya. The Red Sea and the Great Rift Valley open.

2 mya. Several episodes of glaciations (global cooling) start.

20 mya. First anthropoid primates.

15 mya. Flora and fauna alter due to climate change.

4 mya. Early hominids appear and evolve into the human species.

SUMMARY

REVISING CONCEPTS

A B

AB

Look at the stratigraphic redord of an area. Indicate the stratigraphic series and the stratigraphic sequences

Order the events