A still—Volcano—Life—
That flickered in the night—
When it was dark enough to do
Without erasing sight—
A quiet—Earthquake Style—
Too subtle to suspect
By natures this side Naples—
The magma, or light inside the volcano, flickers in the night, when it is dark enough. “Enough,” here, emphasizes a total blackness and suggests a deeper level of hiddenness to protect from revealing “sight” (or keep hidden what goes unnoticed). 
 Note that Emily Dickinson, as observed by many critics, lived the latter part of her life as a “recluse.” Though in isolation, she remained in close contact with her family and continued to read and write. Despite limiting physical contact with others, she continued to write letters, which she did not see as a distraction, but rather stimulation to help her creative writing. As seen in most of her work, Dickinson’s poems often reference her isolation and solidarity of, not only the body, but also the mind. In general, she seemed to think herself separate from society and, as this poem displays, hidden from the eyes and understanding of the others. 
 For more on the life of Emily Dickinson: 
 

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