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Earth's Formation


    1.    Explain how most scientists explain the formation of our solar system.

    2.    Describe Earth's size and shape and the arrangement of its layers.

    3.    List three sources of Earth's internal heat.

    4.    Describe Earth's magnetic feild.

Key Terms:

    inner core        outer core        mantle        lithosphere        asthenosphere        magnetic feild

Notes: (4-1)

The Formation of Our Solar System

There are many views on the formation of the Earth.  Perhaps the most widely accepted version, by scientist, is the nebular hypothesis.  The hypothesis states that our solar system formed around 4.6 billion years ago from a large cloud of rotating dust.  Here are some of the sequences of events.

The solar system originated as a large cloud of rotating dust
Over time the cloud began to condense under the pull of its own gravity while its period of rotation sped up
The birth of the sun - At the center of the rotating cloud hydrogen fission began to take place under great pressure
The remaining dust (~10%) formed the planetary disc where under further condensation the planets (planetesimals) were formed

(zebu.uoregon.edu/~js/ast121/images/ nebular_hypothesis.gif)

Earth's Size & Shape

When talking about the shape of the Earth it is important to remember that the Earth was formed as a rotating cloud of dust.  The result of the compressing and spinning was the formation of a nearly circular planet that bulged at the center.  The actual shape of the Earth is oblate spheriod

The shape of the Earth has been viewed by measuring the Earth's gravitational pull at the poles and the equator.  
It was found that an item weighed 195N at the poles and 194N at the equator.
Since gravity is inversely affected by distance it was reasoned that the item must be further away from the equator at the poles.

(www.uwm.edu/Course/416-125/ 02_location/fg01_009.jpg)

Earth's interior

As the Earth formed from its cloud of dust the heavier materials tended to migrate toward its center of mass.  Over time with frequent collisions of atmospheric particles the Earth's core began to heat up and form.  Additional heat was created from the radioactive materials that accumulated during the formation of the Earth.  Here is the current view of Earth's layers.

Inner core - solid iron and nickle
Outer core - liquid iron and nickle

Mantle - mostly iron, silicon, & magnesium

lithosphere - outer rigid layer of the mantle

asthenosphere - inner puttylike layer

Crust - rigid outer layer of the Earth

(www.educ.uvic.ca/.../earth%20science/ IMAGES/strA.gif)

Earth's Magnetic Field





Last modified: February 02, 2003