This doesn't seem to be clearly answered in the film itself, but Justin Benson, one of the makers of the film, has answered it in an interview:
Benson: You know the Gandalf staff looking things, the rock formations they talk about in the beginning? Those actually form the borders of the different loops. So when you cross into one past that, you come to a different loop each time. If you want to be really specific, the radius or diameter of the circles they form, as it gets bigger, the loop gets longer and as they get smaller, the loops get smaller. So when you see the five second tent, you see them all around it. It’s about a 20 foot diameter. That’s why the guy has such a short loop.
‘The Endless’ Directors Justin Benson and Aaron Moorhead on Toxic Nostalgia and Time Loops [Interview] (page 3)
Of course, this doesn't explain everything: Can the markers be moved or destroyed? Can a time loop be made longer by moving its markers farther out? But it does establish a direct relationship between the two.