Hibernate filled my /root

[Peter Ehlert <pb21a@sdi-baja.com>]

/root partition was 40 GB, about 15 GB was free
/swap 20 GB, unused

hibernate

restart failed

Using Gparted I found /root was full
resized /root to 50 GB
boots properly now

/var/log now contains 29.3 GB
/var/log/syslog 10.0 GB
/var/log/kern.log 10.0 GB
/var/log/syslog.1 4.1 GB
/var/log/kern.log.1 4.0 GB

   I have no clue why this happened
   how do I clean this up and prevent it from happening again?

   PS: I rarely use Hibernate ... can't remember when I used it last, 
if ever