The oceans cover over 70% of Earth’s surface, holding approximately 1.332 billion cubic kilometers of water. With an average depth of 3,682 meters (12,080 feet), this water acts as a liquid veil, concealing a topography larger than all continents combined. Imagining the removal of this water transforms Earth into an alien landscape, revealing the true shape of the planet’s surface. This hypothetical draining uncovers a hidden geography defined by immense plains, a colossal mountain range, and the deepest chasms, fundamentally reshaping our understanding of the world’s surface features.
The Revealed Deep Ocean Floor
Beyond the submerged continental margins, the deep ocean floor would appear as sediment-covered terrain known as the abyssal plains. These plains are exceedingly flat, lying at depths typically between 4,000 and 6,000 meters, and are far flatter than any comparably sized area on the continents. The flatness is due to millions of years of fine sediment, settling from the water column, which has buried the underlying volcanic bedrock topography.
Snaking across this plain is the Mid-Ocean Ridge system, which would become visible as the longest mountain range on Earth, stretching for over 65,000 kilometers. This volcanic structure is where new oceanic crust is continuously formed as tectonic plates pull apart, and in many areas, its peaks are shallower than 3,000 meters. The ridge is characterized by a central rift valley, which runs along its crest, marking the boundary of the separating plates.
In stark contrast to the plains and the ridge, a few narrow, deep cuts would appear, which are the ocean trenches. These trenches, such as the Mariana Trench in the Pacific, represent the deepest parts of the ocean floor, plunging to depths that can exceed 11,000 meters. They are formed at subduction zones where one tectonic plate slides beneath another, creating steep, V-shaped depressions that are three to four kilometers deeper than the surrounding abyssal floor.
Understanding the New Global Coastlines
As the water recedes, the most dramatic geographical change occurs along the continental margins, revealing the submerged extensions of the continents. The continental shelf, the shallow, gently sloping area adjacent to the current coastlines, would become vast new plains. These shelves are relatively flat, typically extending for an average width of about 80 kilometers before reaching a depth of around 140 meters.
The exposure of these shelves would significantly expand the landmass of every continent, creating new territories that were once shallow shelf seas. For example, the entire North Sea between the United Kingdom and continental Europe, as well as large parts of the Gulf of Mexico, would transform into dry, low-lying land. This newly revealed land is composed of thick layers of deposited sediment, carried from continental river systems over millions of years.
The edge of this new land abruptly gives way to the continental slope, a steeper descent that marks the true termination of the continental crust. This slope drops from the shelf break toward the deep abyssal plain, with an average angle around 4 degrees, though it can be steeper in certain locations. The slope is frequently cut by numerous submarine canyons, deep V-shaped valleys carved by sediment flows, which would now stand exposed as monumental gorges.
Ecological and Climatic Catastrophe
The removal of the ocean would trigger a global ecological collapse, beginning with the death of all marine life. Dead organic matter, from microscopic plankton to the largest whales, would be left exposed on the dried seafloor. Furthermore, the dissolved salt, which gives the ocean its salinity, would be left behind, forming vast, thick layers of salt deposits across the newly revealed landscapes.
The absence of the ocean would dismantle the planet’s primary climate regulation system. The oceans currently absorb over 90% of the excess heat trapped by greenhouse gases, acting as a heat sink with a high thermal capacity. Without this moderating influence, global temperatures would experience wild swings, with exposed land superheating during the day and rapidly freezing at night.
The thermohaline circulation, the global conveyor belt of ocean currents that redistributes heat across the globe, would cease to exist. This collapse would mean the end of the weather patterns that sustain life, as the primary source of atmospheric moisture is removed. The world would rapidly become hyper-arid, leading to the desiccation of continental interiors and the failure of the global water cycle as we know it.