40 For the preparation for creation is perpetual and eternal: nor was the frame of this universe actually made by isolated acts of thought, in the sense that first the heaven was thought of, and afterwards there came into God's mind a thought and plan concerning the earth; that He thought of each part singly, so that first the earth was spread out as a plain, and then through better counsels was made to rise up in mountains, and yet again was diversified with hills, and in the fourth place was also made habitable even in the heights; that so the heaven was prepared and the abode of God set apart, and huge clouds in the upper air held the exhalations caught up by the winds; then afterwards sure springs began to run under the heaven, and, last of all, the earth was made firm with strong foundations.
For Wisdom declares that it is prior to all these things. But since all things under the heaven were made through God, and Christ was present at the fashioning of the heaven, and preceded even the eternity of the heaven which was prepared, this fact does not allow us to think in respect to God of disconnected thoughts on details, since the whole preparation of these things is co-eternal with God. For although, as Moses teaches, each act of creation had its proper order—the making the firmament solid, the laying bare of the dry land, the gathering together of the sea, the ordering of the stars, the generation by the waters and the earth when they brought forth living creatures out of themselves; yet the creation of the heaven and earth and other elements is not separated by the slightest interval in God's working, since their preparation had been completed in like infinity of eternity in the counsel of God.
Source: On the Trinity (New Advent)