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DEEPEST PART OF EARTH: The Mariana Trench

Written by: Aidan | Published on: 12 October, 2024

The Mariana Trench is a deep oceanic trench situated southeast of the Mariana Islands in the western Pacific Ocean. Its deepest known point reaches around 11,034 meters below sea level, though the most accurately measured section, called Challenger Deep, sits at 10,911 meters. This makes it the deepest recorded point on Earth’s seabed. If Mount Everest were placed in this trench, its peak would still lie about two kilometers underwater.

Oceanic trenches, like the Mariana Trench, are deep depressions in the seafloor and are a fundamental part of the Earth’s plate tectonics. Over 50 significant ocean trenches exist worldwide, with the deepest located along the Ring of Fire—a zone of volcanic activity encircling the Pacific Ocean. Trenches mark areas where tectonic plates converge, forcing one plate beneath another and forming a deep fissure in the Earth's surface.

First discovered in 1875 by the crew of the H.M.S. Challenger, the trench was later more precisely surveyed by H.M.S. Challenger II in 1951. Over time, further measurements revealed that the trench stretches 2,550 kilometers in length and spans 69 kilometers in width.

What Lies in the Mariana Trench?

The conditions in the Mariana Trench are harsh and varied, ranging from active mud volcanoes to vents that release sulfur and carbon dioxide. Temperatures at the trench floor range from 1–4°C, with no light reaching this extreme depth. Despite the crushing water pressure, which is over 1,071 times greater than at sea level, life persists in these dark, inhospitable conditions.

A mud sample taken from Challenger Deep uncovered about 200 different species of microorganisms, such as microscopic plankton and shelled creatures. Among the trench's inhabitants are xenophyophores—large, single-celled organisms that feed on sediment—as well as amphipods, which are shrimp-like scavengers, and small sea cucumbers known as holothurians.

Larger species also thrive at these remarkable depths, including the hadal snailfish, a translucent, scaleless fish found living at depths of nearly 8,200 meters. Its see-through skin reveals internal organs, and it holds the record for the deepest fish observed on the seafloor. Other fascinating creatures include the deep-sea dragonfish, a predator equipped with oversized teeth, along with dumbo octopuses, zombie worms, and deep-sea jellyfish.

The Mariana Trench has also yielded the deepest rock samples ever obtained from the inner slope, offering valuable insights into the geological history of volcanic eruptions within the Mariana island arc.

In recent years, scientists have even discovered a new virus at a depth of 8,900 meters in the trench, the deepest virus ever found. This virus, a bacteriophage, infects bacteria and is among the most abundant life forms on Earth. Since 2009, more than 3,000 studies on the Mariana Trench have been published, with nearly half focused on bacterial discoveries.

Due to the extreme pressure, humans cannot easily explore the trench’s depths, as most machinery struggles to function under such conditions. Despite these challenges, scientists continue to seek innovative ways to gather more data, suggesting that much of the trench remains a mystery waiting to be explored.