scons describes running phases itself. Running it over an empty SConstruct yields this:

$ scons
scons: Reading SConscript files ...
scons: done reading SConscript files.
scons: Building targets ...
scons: `.' is up to date.
scons: done building targets.

To suppress phase messages, add -Q option. --tree=all allows to see dependency tree for current target that scons constructed while building.

$ scons -Q --tree=all
scons: `.' is up to date.
+-.
  +-SConstruct

. is default target, which means "build SConstruct in current directory". SConstruct is then a dependency for building the default target.