One of the Berachot that we recite each morning as part of the Birkot Ha'shahar series of blessings is "Roka Ha'aretz Al Ha'mayim." This text is based on a verse in Tehillim (136:6) in which King David gives praise to G-d for the wonder of the earth being spread over the water. Water lies underneath the earth, and since earth is much heavier than water, the earth should sink into the water, making the world uninhabitable. If we throw a mound of earth into water, it will of course sink to the bottom of the water, and yet, miraculously, the earth remains afloat, allowing us to live here. This is an ongoing miracle which we are unlikely to be cognizant of, because we don't see the water. King David appreciated this wondrous phenomenon because he saw what could happen without it. The Gemara relates that when David laid the foundations for the Bet Ha'mikdash, the underground water began rising, and threatened to flood the entire earth. He needed to utilize one of the Names of G-d to make the water return to place. We catch glimpses of the threat that would be posed by the underground waters when we see or hear of a tsunami, whereby the ocean waters expand into the shoreline. The Sages wanted us to appreciate this miracle on a daily basis, and so they instituted a special blessing for us to recite each morning praising Hashem for keeping the earth above the underground waters. The Ben Ish Hai (Rav Yosef Haim of Baghdad, 1833-1909) notes that this Beracha is unique in that, as opposed the other morning blessings, it does not speak of a phenomenon that is renewed each day. The other Berachot we recite in the morning praise Hashem for blessings He grants us anew every day – such as the ability to get out of bed, to open our eyes, to put on our clothing, and so on. The earth's floating on the underground waters, however, is a continuous condition that never ceases; this is not something which is discontinued during the night and then resumes in the morning. The Ben Ish Hai writes that precisely for this reason the Sages deemed this phenomenon worthy of a special Beracha – because it is a constant miracle, as at any moment the earth would sink if not for Hashem's kindness. The Rabbis instituted this Beracha to draw our attention to this wondrous reality so we recognize our enormous debt of gratitude to the Almighty.