the geological history of earth

The geological history of the Earth


Can be traced with the help of
 Sedimentary rocks: composed of layers

 Relative position of layers – information about the

relative age

 Fossils

Scientists
produced
a geological
With the help
of these:
timescale


Geological timescale
 Divided into units

 Larger units = ERAS
 Precambrian

Represent major phases in
the evolution of the planet

 Palaeozoic
 Mesozoic

 Cainozoic

divided into periods
into epochs
into ages




The earliest events
 The Earth is

4,6 billion

years old

 Formed from a huge cloud of gas and dust
 Meteorites played an important role in the early life,

added to its mass

The energy of collisions and nuclear
fission generated heat

Material became VERY
HOT


High temperature …
 Led to the chemical differentiation

of the material into different layers
 Iron and nickel sank into the centre
 Less dense materials formed

concentric layers around the core

 The young Earth had an atmosphere – it was lost


The Precambrian


The longest era
 Represents 87% of the geological history

 Divided into 2 parts
1.

Archeozoic

2.

Proterozoic


1. Archeozoic
 continuous decrease of temperature
 water – liquid
 plates of the lithosphere had been formed

 volcanic activity:

 result : The
Composed
of atmosphere
first Permanent

carbon
dioxide,
ammonia,
steam



Oxygen
 Appeared later in the atmosphere
 The result of:
1.

UV radiation

2.

Photosynthesis

(after the appearance of plants)


The temperature of the surface became
cooler…

 Under 100˚C

Steam
precipitated

The first ocean
was born


Stromatolites
 Provide the first geological evidence of life
 Rocks with special spherical structure
 Blue algae play an important role in their formation

 The oldest 2,9 billion years old

(Being formed in
present day Australia)


2. Proterozoic
 Began 2,5 billion years ago
 Several orogenies – produced

the oldest parts of the crust = the so-called shields
 Shields form the core of continents
 They were originally mountain ranges which were eroded

later

 Later orogenies did not change them (!)



The Palaeozoic


1. Period: Cambrian
 The first fossils – animals with hard parts (Skeletal

material)

 Living beings could only be found in seas and oceans
 The atmosphere did NOT filter the radiation of the

Sun

Continents were NOT
suitable for life


(3.) Silurian period
 Plants were the first to conquer continents


(4.) Devonian period
 The most significan changes: plants spread on land

and the first animals appeared on continents

2 important orogenies
 I. Caledonian: Silurian period
 Connected N America and Europe

 Scandinavian Mountains
 Mountains of Scotland

Caledonides

 East Greenland
 Northern section of the Appalachian Mountains



II. Variscian: Carboniferous period
 Connected Gondwanaland with the complex of Europe and N America
 + Asian areas were added by
 the Ural Mountains

 South England
 France
 Mountains of Germany
 The mountains surrounding the Bohemian Basin
 Rhodope
 Great Dividing Range in Australia
 Southern section of the Appalachian Mountains
 Velence Mountains

By the end of the Palaeozoic
 All continents had been connected
 Huge continent = Pangaea

 Surrounded by one huge ocean = Panthalassa

 Huge bay in the eastern part of the continent: Tethys