Stanza 5 Summary

Get out the microscope, because we’re going through this poem line-by-line.

In their old anarchy to the horizon-line.

The poem whips out some enjambment here, completing the sentence of the previous line.
So, our speaker is carrying over that image of the "fluted bones and acanthine hair" and shows these colossal fragments stretching out to the horizon.
It's kind of like the movie camera just pulled out for a wide shot and now we see just how big the Colossus was.
All of this really helps us feel how massively devastating the loss of the speaker's father was for her.
The use of the "old anarchy" not only paints a picture of the chaotic ruin spreading around the speaker, but also gives us a sense of just how long it's been there.
We're reminded that this is a pain that the speaker has been dealing with for a while.

It would take more than a lightning-stroke
To create such a ruin.

Here, the speaker again helps us see the vast destruction that's spreading all around her.
It wasn't just some pip-squeaky flash of lighting that did this; it was something bigger and way more powerful.
Could this possibly be a reference to the earthquake, which took down the original Colossus of Rhodes? Could it be a reference to nuclear weapons, which were still relatively new to the world when Plath wrote the poem?
Whatever it is, the speaker again gets across the idea that her father's death was accompanied by some major-league devastation.

Nights, I squat in the cornucopia
Of your left ear, out of the wind,

The speaker has taken us through her day of work and now we see how she spends her nights, taking shelter from the wind in the statue's ear.
The description of the ear canal as a "cornucopia" is pretty great, in our humble opinion. A cornucopia is one of those kinda curvy, cone-shaped things that you usually see spilling over with the fruits of the harvest.
So, the shape of it is actually a whole lot like an ear canal.
It's interesting that the speaker chooses to use this symbol of thriving life in a poem that's so focused on ruin and death.
Could it be a reference to the fact that she still gains some kind of sustenance from the memory of her father?
Or, to go the totally opposite direction, could it represent the lack of sustenance, since the cornucopia-shaped ear canal would have to be empty for her to take shelter in it?