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.
Puzzled by Power. Dear PbP, We're not sure how it all started, but the idea that it's harmful to shut your computer down every night is a myth. Unless you shut it down incorrectly (e.g. ripping out the power cable and laughing maniacally), there's really nothing to worry about. In fact, shutting down your computer every night offers a few advantages. First and foremost, it won't draw as much power when off. Additionally, you don't have to remember to turn off the sound each night so it doesn't wake you up with an unexpected alert.