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Copyright Len Bruton1 Lecture 3 Planet Earth
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Copyright Len Bruton2 Lecture 3 – Planet Earth Solar nebula accreted to form the solar system Earth accreted (probably from solar nebula) about 4,600 million (i.e. 4.6 billion) years ago due to electromagentic and gravitational forces – self organization Earth is the third planet out from the Sun Diameter of 12,776 kilometers Earth is much smaller that Jupiter, Saturn, Uranus and Neptune Geologic record begins 3,900 million (3.9 billion) years ago
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Copyright Len Bruton3 Lecture 3 – Planet Earth Early Earth, over 4 billion years ago, was molten and meteorites impacted the surface Lighter liquids floated to the surface Heavier liquids sank to core, such as iron and nickel Lighter liquids gassed out of volcanoes and formed early atmosphere Stable crust formed at surface
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Copyright Len Bruton4 Lecture 3 – Planet Earth - 0 to 3.5 billion years Early atmospheric gases from volcanoes were probably carbon dioxide, carbon monoxide, water vapour (i.e. steam) and methane - but no oxygen. A hot humid and violent place. Earth has a solid crust on a molten liquid core The crust is segmented into floating continental plates The molten core drove continental drift in a process called tectonics Read the excellent description of Continental Drift at NASAContinental Drift Animation of Continental Drift over last 800 million yearsAnimation of Continental Drift
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Copyright Len Bruton5 Lecture 3 – Planet Earth - 0 to 3.5 billion years As the Earth cooled to below 100 degree centigrade, water vapour from volcanoes probably condensed out to form oceans Early Earth life may have started without oxygen, in the seas – algae over 3,500 thousand years (about 3.5 billion years) ago – that is, life had already started by 30% of the current age of the Earthin the seas The Panspermia theory – Life may have kick-started outside EarthLife may have kick-started outside Earth Cyanobacteria
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Copyright Len Bruton6 Lecture 3 – Planet Earth The Current Composition The crust is very thin – only 1/500 th of the diameter
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Copyright Len Bruton7 Lecture 3 – Planet Earth – the Last 500 million Years Photons from the Sun are thought to have provided the energy for water vapour to split into oxygen and hydrogen leading to oxygen-feeding life forms about 2 thousand million (i.e. billion) years ago Starting about 500 million years ago, the oceans became steady- state chemical sources of life Two-thirds of the Earth is covered by the oceans The sea floor spreads and continents drift on their plates The molten core causes a magnetic field around Earth which protect Earth from radiation and allowed the atmosphere to develop
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Copyright Len Bruton8 Lecture 3 – Planet Earth – the Last 500 million Years Periodic Ice Ages have occurred over these 500 million years Outstanding detailed slide presentation of The Ice AgesThe Ice Ages
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Copyright Len Bruton9 Lecture 3 – Planet Earth – The Last 150,000 Years of Unsettling Climatic Years Dramatic climate changes have occurred from full Ice Ages and glacial coverage to non-glacial warm periods Transitions from Ice Age to warm periods have occurred in less than 10,000 years and we do not know the reasons.
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Copyright Len Bruton10 Lecture 3 – Planet Earth – The Last 150,000 Years of Unsettling Climatic Years
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Copyright Len Bruton11 Lecture 3 – Planet Earth – The Last 150,000 Years of Unsettling Climatic Years Solar variations, volcanic activity, space dust, asteroids, etc. are theories that might be the reason Humans have expanded across the planet since the last Ice Age, over the last 20,000 years, taking advantage of the highly favourable period between Ice Ages Excellent article relating human development and ice ages: Ice Ages and Big Brains: Climate Change and Human EvolutionIce Ages and Big Brains: Climate Change and Human Evolution
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