Please give an explanation of these lines from "Ode to the West Wind."
Thou who didst waken from his summer dreams
The blue Mediterranean, where he lay, 30
Lull'd by the coil of his crystàlline streams,
Beside a pumice isle in Baiæ's bay,
And saw in sleep old palaces and towers
Quivering within the wave's intenser day,
All overgrown with azure moss, and flowers 35
So sweet, the sense faints picturing them!
Thou For whose path the Atlantic's level powers
Cleave themselves into chasms, while far below
The sea-blooms and the oozy woods which wear
The sapless foliage of the ocean, know 40
Thy voice, and suddenly grow gray with fear,
And tremble and despoil themselves: O hear!
You have quoted the third stanza from this terrific poem in its entirety. Of course, there is always a danger of just looking at specific parts of a poem separately and not in the context of the poem as a whole, so when you have finished reading my response I suggest you go back and see how this stanza fits in to the poem as a whole.
This stanza begins with the poet addressing the West Wind (what is known as an apostrophe), and talking about the wind's impact on the sea. The wind is shown to stir up massive waves, disturbing the ocean as if it was waking somebody from a dream. The Mediterranean is pictured as a man asleep who is woken up by the wind's power. A much more violent picture of the wind is presented later on in the stanza, especially when the wind's impact on the Atlantic is described. The "Atlantic's level powers / Cleave themselves into chasms" in response to the wind, and its power is so great that even the "sea-blooms and the oozy woods" of the ocean "suddenly grow grey with fear" when they hear the wind coming. This stanza therefore serves to reinforce the power and majesty of the wind by focusing on how it impacts the sea.