OS X accessing external drive
Based on your screen shot it is reading/writing the same thing over and over = Kindle!

For some reason Spotlight thinks the Kindle has made changes to the drive and it is re-indexing it.

To find out if that is the problem disable Spotlight and check.

Disable Spotlight

sudo launchctl unload -w /System/Library/LaunchDaemons/com.apple.metadata.mds.plist


and 

Enable Spotlight

sudo launchctl load -w /System/Library/LaunchDaemons/com.apple.metadata.mds.plist


To disable the External drive indexing by Spotlight:


Connect the volume or drive you want excluded to your Mac.
Open the System Preferences application.
Click on Spotlight, then click on the Privacy tab.
Drag your volume or drive into the Privacy menu to exclude them from Spotlight's indexing.