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.
Shutting down your PC at the end of the day is so 20th century. What you probably should be doing is putting it into sleep mode. You'll save that interminable wait for your system to boot up, and it won't destroy the Earth or your bank account with a dramatic change in energy usage.