Q. how does geoLOD work?
http://www.web3d.org/documents/specifications/19775-1/V3.3/Part01/components/geodata.html#GeoLOD
- it has 2 levels of detail
- it unloads the non-selected level
- and loads the selected level of detail
rootUrl
rootNode
child1URL - child4Url
children 

There's no mention of unloading rootnode. Presumably it's just not displayed when its level isn't used.
Mars
LOD
child1 = 0000
root = shape
LOD
child1 = 0003
root = shape
LOD
child1 = 0006
root = shape
LOD
child1 = 0009
root = shape
LOD
child1 = 0012
root = shape
LOD
child1 = 0015
root = shape
LOD
child1 = 0018
root = shape
LOD
child1 = 0021
root = shape
=============================
0000
LOD child1 = 001
root = shape

0003
LOD child1 = 004
root = shape

006
LOD child1 = 007
root = shape

009
LOD child1 = 010
root = shape

012
LOD child1 = 013
root = shape

015
LOD child1 = 016
root = shape

018
LOD child1 = 019
root = shape

021
LOD child1 = 022
root = shape
===================================
001
LOD child1 = 002
root = shape

004
LOD child1 = 005
root = shape

007
LOD child1 = 008
root = shape

010
LOD child1 = 011
root = shape

013
LOD child1 = 014
root = shape

016
LOD child1 = 017
root = shape

019
LOD child1 = 020
root = shape

022
LOD child1 = 023
root = shape

==================================
002
root = shape

005
root = shape

008
root = shape

011
root = shape

014
root = shape

017
root = shape

020
root = shape

023
root = shape

Pattern: the root scene holds an octet, but only one child per LOD.
The one-child-per-LOD and root=shape perculates down till leaf has a root shape and no child url.
Mars -> 000 > 001 > 002
Mars -> 003 > 004 > 005
Mars -> 005 > 007 > 008
Mars -> 009 > 010 > 011
Mars -> 012 > 013 > 014
Mars -> 015 > 016 > 017
Mars -> 018 > 018 > 020
Mars -> 021 > 022 > 023

All of mars 8 root shapes get loaded with mars.
When approaching mars, 8 children kick in.
Closer, another 8 children kick in.
There's no 1:4 quadrant refinement. It;s 1:1 refinement. So the shapes keep getting fatter as you approach.
IF root is not unloaded until its scene is unloaded, and assuming we approach about the same rate, it could mean _all_ LOD scenes are loaded at some point close to mars.
It would be as you back away that children get unloaded, presumably in reverse order approximately to how they were loaded.