Scientists have thought that magmas that form new crust at fast-spreading ridges rise up from the depths, quickly crystallize, and then push away from the ridge to form new ocean floor.
To stop a computer from overheating never keep a cloth or something else on the CPU or monitor. Also use the save energy option from properties so as to switch off the monitor when not in use. This will always help in keeping the computer cool and not overheating it.
Sometimes, faulty capacitors or some problem in motherboard circuitry can also cause the computer to overheat. Get it checked from a computer repairshop. If your computer shuts down by itself, then it is possible that anyone of the above reasons, may be the cause of it.