Sounds like your graphics card is caching to your hdd? how much graphics RAM is on your 970? 2GB? 4GB?
Or you have somethihng running in the background eating your disk like background virus scan (some bugged avast updates can send that program into spazz mode and kill your cpu/disk by scanning everything continuosly, so all antivirus programs can do the same).
Youre playing in high/ultra detail? generally most games take 3gb at 1080p on very high settings, and if youre using the same card to power your desktop ... well you know whats gonna happen. first the vram overflow tries to cache to your system ram, and if thats full, its going to try your pagefile.
So solution if you have the 2GB 970: readyboost. readyboost sits between your system ram and the pagefile, and the vram will prioritise readyboost space. Im sure you got a spare 4GB-16GB usb/sd card laying around, the fastest possible solution is to whack it in, turn on readyboost and start up your games.
If readyboost isnt helping, then you have a program running in the background whilst youre playing? check task manager, open the resource monitor and see what program(s) are using your disk activity ... kill the unwanted program.