One of the first things our lecturer said to the class at the start of the semester was
“If aliens are observing our planet from far far away, they wouldn’t really call it earth. If you look at the structure, our planet is one that should actually be called The Ocean “
As we go through the pell mell of our daily lives, little attention do we pay to the fact that there lies a colossal body of water, mostly unexplored and that the land on which we are sitting (of which all the continents are made of, but which apparently is still huge by our standards), covers a mere 29.2 % (i.e. less than 1/3rd) of our planet’s surface area.
But the body of water is just the tip of the iceberg; what’s more fascinating than anything else is what lies within and beneath that water. There is more ecosystem and biodiversity flourishing in those waters than you will ever be able to imagine. But let’s put aside the marine biota for the moment and explore what lies underneath the massive body of water.
Have you ever imagined what would happen if you were able dive down to the very bottom of the deepest parts of the sea? Is there even a bottom at all? The answer is a fascinating yes!. It is fascinating because the ocean floor is completely different from what you would imagine it to be. This is because the sea floor is undergoing tremendous amount of tectonic activity (movement), every moment; with the new crust being formed and the old one being subducted.
One important realization is that the continental margin doesn’t end as you start moving offshore; not until you have reached hundreds of kilometers. The ocean basin, on the other hand is not a flat land like you would imagine. It contains several features such as:
Abyssal plains – These are very flat depositional surfaces formed by slow settling of fine particles.
Volcanic Peaks – These poke through the sediment cover of the abyssal plains and depending on their elevations can be of various types (seamounts, tablemounts/guyots, seaknolls and volcanic Islands ).
Ocean Trenches – These are linear, steep sided scars on the ocean floor and contain some of the deepest parts of the oceans. They form volcanic arcs such as the Island arc (e.g. Japan) and the continental arc (e.g. Andes mountains) due to the rise of the trench on the landward side. The Pacific Ring of Fire is formed from these trenches.
The Mariana Trench, situated at the Western Pacific is the deepest part of the ocean/world (about 11,022 km below sea level). No feature on Earth is as tall as the Mariana Trench is deep.
Mid-Ocean Ridge – It is the longest global mountain chain entirely volcanic that marks the divergent plate boundary (i.e. where the two lithospheric plates are moving apart from each other). The molten lava from the bottom spews out through the fractures/cracks known as hydrothermal vents, cools down and forms the new sea-floor pushing the old ones toward the continental margins.