World Builders™                                                                            Session Two  --  Geology             

          Forming the Rocky Surface of Your Planet  

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After many thousands of years your planet will become a world with a solid surface.

     As the cloud of dust particles and frozen gas crystals swirled around your proto-sun, little grains of matter bumped into each other and stuck together.  Gradually the gathering grains became clumps and lumps which grew larger and larger as gravity pulled some of them together. It is hard to imagine entire planets coming together by this process, which is called accretion, and it took a long time.  However, scientists believe that this is how planets and moons come into being.

     Read the science notes about The States of Matter.  You will see that, as matter goes from a gas to a liquid and then to a solid, the electrons,. which help to make up the atoms, have less and less space in which to jump around.   The more matter that there is, the more gravity there is, and eventually the atoms in the middle of the proto-planet get hotter and hotter as they are squeezed closely together.  What happens then?  Well, what happens when you put twenty five people in a phone booth all together?  Right!  The atoms heat up, the electrons struggle, and after a while the whole planet melts into a very hot ball of molten rock.  

     By the way, this is why planets are more or less spherical.  They are already spinning, and gravity is pulling all the atoms toward the center of the ball.  It is during this molten stage that they are smoothed and rounded.  To us the earth seems to have great heights and depths, but, by comparison, its surface is as smooth as the skin on an apple!  Even today, water rushes downhill, carrying mud and gravel to the lower parts of the landscape.  This helps to keep the planet roune!

     Other things happen when a planet becomes molten. The heaviest elements, including much of the iron, are pulled to the center of the molten ball.   Radio-active elements also sink, and contribute to the long term heat in the center of the world.  Lighter elements float to the top, where they later become the continents. As a rocky  planet cools, a crust forms on the outside.  As the rock cools further, cracks develop. Under the crust the rocky material is still very hot, and so somewhat plastic, like very, very thick cookie dough. The plates of rock that crack apart on the surface float on this hot material, and slowly drift apart or collide on the planet's surface.   We will be learning more about these floating tectonic plates.

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Your group will work to

  • decide on the high and low places on your planet

  • draw maps to show land and water areas

  • draw relief maps of your planet, showing mountains, lakes, and rivers.

  • Name your continents and oceans.

  • Write a description of the geological features of your planet

  • Try to figure out where your tectonic plate boundaries probably are and put them on one of your maps.  You will need to explain your thinking

  • draw sketches of your planet's landscapes

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Bring to class next session:

  • a written description of the geology of your planet.
    Include information on the land and water areas.

  • Download and use Fractal Terrains to draw relief maps, rainfall maps, biome maps and climate maps of the planet.   Save these maps as .jpgs for use in your own work.
    Note that the trial period for the use of Fractal Terrains lasts for two weeks.

  • Bring your maps to share with your co-workers.

Page is due Week Four

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© 1999, 2003. Elizabeth Anne Viau. All rights reserved. This material may be used by individuals for instructional purposes but not sold. Please inform the author if you use it at