is this a boulder? im confused. i see this everyone around the map.

can someone explain this?  

On a serious note,
those are stakes. Stakes meant to be hit with the hammer item, which is unobtainable outside of the FFA events held in the MoD Carnival.
It is looking unlikely that the hammer will ever be added to the game, so those chests are either a developer oversight or a tease at this point, rather than a feature.  

There was an item on the original Classic server, a hammer, that would allow you to smash these and then run over them (which would let you access these chests)

Pretty sure they're supposed to be wooden pegs stuck into the ground  

Original Hammer:

 

Posted by 4-Lom

Original Hammer:

m̶o̶r̶e̶ ̶l̶i̶k̶e̶ ̶o̶r̶i̶g̶i̶n̶a̶l̶ ̶g̶r̶a̶a̶l̶ ̶a̶s̶ ̶a̶ ̶w̶h̶o̶l̶e̶  

Posted by ZedFox

m̶o̶r̶e̶ ̶l̶i̶k̶e̶ ̶o̶r̶i̶g̶i̶n̶a̶l̶ ̶g̶r̶a̶a̶l̶ ̶a̶s̶ ̶a̶ ̶w̶h̶o̶l̶e̶

Don't leak the secret formula