It's been billions of years since Pangea brook apart. Think of all of the forces that have acted upon those continents since. Erosion from water is a big part. Islands have broken off; earthquakes have shifted continents; glaciers have formed, mountains have formed by continents being smashed together. It wasn't a clean cut. Imagine having week old birthday cake left overs. Already when it was fresh and you cut it, crumbs fell off and the cutting wasn't neat. Now a week later as you're trying to pick up an already cut piece, the frosting is falling off and taking pieces of cake with it and it's crumbling. It isn't a perfect fit because time has altered the shapes of the continents.
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<span>Pacinian corpuscles are rapidly adapting mechanoreceptors so they respond only at the onset and offset of the stimulus. The Pacinian corpuscle has a single afferent nerve fiber. Its end is covered by a sensitive receptor membrane whose sodium channels will open when the membrane is deformed in any way. Pressure thus causes sodium to enter the neuron and create a generator potential. If this potential reaches a certain threshold nerve impulses are formed. This impulse is now transferred along the axon with the use of sodium channels and sodium/potassium pumps in the axon membrane. The magnitude of the stimulus is encoded in the frequency of impulses generated in the neuron. So the more massive or rapid the deformation of a single corpuscle, the higher the frequency of nerve impulses generated in its neuron.</span>