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.
A more rare cause of a computer shutting down randomly can be a computer virus. Some computer viruses will actually shut off your computer, and then turn it back on. These viruses are usually activated by a certain thing you do on a computer, whether itâs a keystroke or opening a particular program.