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Formation and Evolution of the Moon |
Take the Quiz == page down to the bottom of these lecture notes.
We start first with a comic drawn by an Astronomy 150U student from the Summer of 1999. Here it is: Earth and Moon by Richard Swarts
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| Pre-Imbrium Event; 4 billion years ago | Asteroid Impact | Shock of Impact Spreads | |
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| Dust and Heat Subside | Ejecta Covers Old Craters | Lunar Mountains are Rims of Huge Craters | |
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| Lava Wells Up; Basin Fills | Lava Flooding Nearly Complete | Final Thick Lava Flow | |
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These slides are from the UW Astronomy Dept. slide collection. The original paintings were published by Hansen Planetarium, Salt Lake City, Utah. Contributors: Don E. Wilhelms and Don E. Davis, US Geological Team. | |
| Mare Imbrium; 3 billion years ago | The Moon Today |
The Origin of the Moon by Greeg Herres and William K. Hartmann (highly recommended!)
Computer Model of the Formation of the Moon (animation from Theories for the Formation of the Earth's Moon -- University of Massachusetts)
One Giant Impact for Moonkind Harvard Magazine
The Earth's Moon from "The Solar System" lectures at the University of Tennessee.
Where No Man has Gone Before: A History of Apollo Lunar Exploration Missions (W. David Compton)
mare
highlands
complex impact crater
simple impact crater
secondary craters
chain craters
ghost crater
straight rille (fault)
sinuous rille (lava channel)
central peak
rays
wrinkle ridges
impact basin
That which lies on the top is youngest; that which lies on the bottom is oldest. That which overlays another feature is younger than that feature. Think if you were to build a house. The foundation comes first, then the walls, then the roof (non-module home). If you investigate layers of sedimentary rock in geology, the oldest rock would be on the bottom and the most recent would be on top.
Another example: we have a new kind of candy bar on the left. Its layers were laid down on an assembly belt: milk chocolate, nuts mixed with white chocolate, creamy caramel, raisins mixed with coconut, and on top a layer of dark, semi-sweet chocolate. On the right, an event that came after the formation: the big bite. The "big bite" gives an example of the "Law of Cross-Cutting Relations" -- the bite is younger than all the rocks that it cuts across. If there were to be additional layers of chocolate on top of the bite, then the bite is older than those layers. An additional clue would be given by the fact that the layer on top of the bite would fill in the hole.
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Here is a more realistic example from the US Geological Survey: Fossils, Rocks, and Time
THE LAWS OF SUPERPOSITION AND CROSS-CUTTING RELATIONS |
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The basalt flow shown here obeys the Law of Superposition. It is younger than the beds below it and older than the beds above it. Note that the molten rock of the volcanic flow has baked the rock underneath it. The bed above was deposited long after the flow had cooled and hardened and has not been baked. Numeric ages from the flow and dike and relative ages from the fossils in the surrounding rocks contribute to the geologic time scale. The granite dike (a mass of rock that cuts across the structure of the rocks around it) shown here illustrates the Law of Cross-Cutting Relations. The dike is younger than all the rocks that it cuts across and older than the rocks above it that it does not cut. Note that the contact between the dike and the rocks around it has been baked by the heat of the molten granite. |
Use the rule of superposition and decipher which animal walked across the sand first, second, and so on to the animal that crossed last.
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