Part B: How the Mantle and Crust Respond to the Gravitation of the Passing Comet Moon.
As the comet moon approaches the Earth it's gravitation tries to stretch the Earth in the comet direction into a rugby ball shaped ellipsoid. If the Earth's mantle was elastic, (ie it could stretch) then the Earth would just stretch as the comet passed. But because the mantle and crust are essentially rigid the only way to accomplish the rugby ball shape change is for the mantle to shear into huge wedges that reach from the outer liquid core to the crust. Typically the whole of the globe would separate into maybe 10 - 30 tectonic wedges. The question arises - why should the mantle fragment in such a way as this ? The answer is - because the forces exerted by the comet as it is passing are massive and the material which makes up the mantle is essentially rigid. Huge tensions within the Earth give way to fracturing of the mantle and crust accompanied by massive Earthquakes around the World. After the fracturing has occured the gravitation of the comet imparts accelaration to each tectonic wedge whose motions go on for many months. The reason that the motions go on for many months is because the motions of each wedge are virtually friction free being bounded by molten lava at each wedge boundary. Accompanying the shape changes are potentially thousands of earthquakes around the World as wedges slip with respect to each other. A certain fraction of these earthquakes will result in tidal waves that can flood low lying continental regions around the World. Earthquakes however only cause small scale flooding at coastal regions and are not the cause of the global flood that follows.
Diagram 1 below shows how the comet tries to stretch the Earth in the comet direction.
Diagram 1.) Elastic Stretching with no breakages.
The Earth doesn't respond in this way however. To accomplish the shape change the Earth's mantle develops radial fractures from the liquid core to the outer crust creating huge isolated tectonic wedges, which slide with respect to each other. Diagram 2 below shows this principle.
Diagram 2.) Fracturing and Sliding.
Typically the comet approaches fast at a velocity of 50 - 60 km per second. Ultimately it reaches a minimum distance of 20,000 km with a residence time of about 400 seconds at this distance. This is time enough for the mantle to respond to the comet's gravity. After the 400 seconds are up the comet begins to recede from the Earth and travels on in a new trajectory.
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