marked safe is a notification feature that tells you when those you follow have marked themselves as safe in an area affected by a disaster or other physical emergency within a geographical area.
Facebook has supported "marked safe" as a notification and as an opt-in feature for those wanting to mark themselves as safe since 2013?
2016-07-14 Screenshot of notification from the "globe icon" drop down list:
Text notification example from an actual notification seen 2015-11-13
[image of person1] Person1, Person2 and 4 others were
marked safe during DisasterEventName.
29 minutes ago
- "Person 1" is the most recent person that has marked themselves safe, "Person 2" is the second most recent, etc.
- "4 others" is the summary of however many other people you follow were marked safe
- "29 minutes ago" is the time since the most recent person has marked themselves safe.
- DisasterEventName is the name given to the disaster (apparently) by Facebook.