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Lecture 2

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University of Toronto Mississauga
Earth Science
Lindsay Schoenbohm

Lecture 2 The Big Bang Theory • 13.7 billion years ago – all the matter of the earth was compacted into a small spot  began to expand rapidly and initially had several light elements, neutrons ,etc – got super- heated and was unevenly distributed – formed lumps and grew • Stars form and explode in several cycles. Larger elements form thru fusion • Our galaxy : milky way  we are in solar system that surrounds sun Formation of Solar System and Earth • Nebula : forms from hydrogen helium and heavier elements left from big bang, and previous star cycles • The nebula condenses into swirling disc, w/ central ball surrounded by rings • Ball at center grows dense and hot enough for fusion  becomes sun • In the rings, dust particles collide and stick together, forming planetesimals  not as big or round as planets but getting bigger – eventually these planetesimals collide and grow into proto-earth. Interior heats up and becomes soft. • Collision creates energy and makes heat • Gravity reshapes proto-earth into sphere. Interior differentiates • It is likely the planet had iron and then wrapped completely with molten  would have cooled quickly and created the crust Formation of Moon • Formed thru gigantic collision • Moon also had iron core and molten mantle  collided with earth and when it did some stuff was left on earth – creating a ring of dust around earth  this ring of dust eventually collided back with the moon – created the moon Earth’s Interior • Series of layers : inner core (solid) and outer core (liquid iron), mantle, crust • Total radius of planet = 6371 km • Crust o 0.5% of volume, 7-70 km thick  varies – had to do with plate tectonics • Mantle o 67% of volume, 2885 km thick Just know mantle makes 1/3 of earth, crust insignificant compared to everything else • Outer core Lecture 2 o 30.8% of volume, 2255km thick • Inner core o 1.7% of volume, 1216 km thick How do we know? 1. Experiments that mimic core conditions (3.6 million times “atmosphere pressure) a. E.g. take 2 diamonds push together and use laser to create high temperatures – to simulate temperatures of the earth’s interior (such as mantle, etc) – use to look at properties of earth’s interior, etc These models are limited by our 2. Computer models understa
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