The opening line of the song is "I dig 'til my shovel tells a secret", which uses personification as a poetic device. The image of a shovel telling a secret emphasizes how isolated the singer is, all he has to talk to and confide in is this tool rather than another person. Later in the song, the line "echo wide as the equator" again creates a sense of isolation - the whole world is empty and the echo just keeps going, even that is abandoning the speaker. Conversely, this line also creates a sense of unity. The speaker's experience is echoed across the globe; everyone experiences struggles and tries to deal with them alone and no one really succeeds.
The artist also creates vivid and expressive imagery by using multidimensional language. One such example is the use of the word "tremble" in the line "fault lines tremble underneath my glass house". Tremble creates a sense of wariness, like something is about to break and give way, a sense which is certainly aided by the image of a glass house. However, it also creates a sense of fear and almost timidness, which would probably be more related to the afraid speaker than the impending destruction.
Another example of multidimensional language is the word 'exonerate' from 'I bend the definition / of faith to exonerate my blind eye". Exonerate can have two meanings - one is to excuse something from wrongdoing. This definition would apply to the speaker's attempts to ignore the mistakes he's made and the mess he's made, even though he knows it's not right to do so. He pushes away the negatives and makes excuses for himself so he can keep doing things the same way, even though he knows it might benefit him to take another course of action. This ties into the second definition, which is to excuse someone from duty. Perhaps the speaker feels as though this system of faking it even as his life is in shambles is less of a choice than it is a necessity in order to keep moving forward. He knows it is a precarious situation but he doesn't know quite how to take a new path, but he hopes that he will be exonerated and given a chance to re-do things and fix his life up.
"Earth" by Sleeping At Last is an example of musical poetry. The song itself is an insight into the troubled nature of human existence and how close we all are to falling apart, yet we keep soldiering on until the destruction gets too great and we are forced to stop and begin again in a new light. The artist uses personification and hyperbole to help the listener visualize and relate to the image of humanity being presented, as well as multidimensional (and multidefinition-al) language to accentuate the nuanced emotions that the song captures.