More recently introduced terms such as 'annually laminated' are synonymous with varve. Of the many rhythmites in the geological record, varves are one of the most important and illuminating in studies of past climate change. Varves are amongst the smallest-scale events recognised in stratigraphy.
PCs are designed to shut down automatically when heat endangers the hardware. To find out if this is your problem, download and install Speedfan. It's small and free. Although Speedfan's basic job is controlling the speed of your PC's fans (you probably guessed that by the name), it also provides the CPU temperature.
This is purely an environmental issue. Overheating can cause system freezes. The CPU is the great concern as it is extremely sensitive and integral to the functionality of the computer. Many computer users describe certain noise when the fanâs ball bearing goes out â similar to a hissing snake.