The depths of the ocean have always been a source of mystery and fascination for humans. While we have made great strides in space exploration, the ocean floor remains largely uncharted territory. With an average ocean depth of 3.7 km and the deepest part of the ocean – the Challenger Deep in the Mariana Trench – plunging to a staggering depth of 10,935 m, it is no wonder we are fascinated by what lies beneath the bottom.
In addition to the mesmerizing array of unique and unusual creatures that inhabit the ocean depths, there is a world of rocks and geological wonders waiting to be discovered. Like land, the ocean floor is made up of rocks, albeit with some intriguing differences.
The Earth’s crust, which forms the base of our continents, is highly variable. Its thickness under land averages about 30 kilometers (19 miles), and under mountain ranges it can be as thick as 100 kilometers (62 miles). In contrast, oceanic crust is relatively uniform, with an average thickness of 6-7 km (3.7-4.3 miles).
The continental crust, consisting mainly of igneous granites, transitions into continental slopes as it enters the ocean. These slopes are composed of granitic and sedimentary rocks formed under tremendous pressure. As we go deeper into the ocean, we encounter the ocean floor, which is composed primarily of mafic oceanic crust. This crust consists mainly of basalt and gabbro.
Basalt, like other igneous rocks, is formed by the rapid cooling of molten rock. There are amazing features in the deep ocean known as “mid-ocean ridges.” These ridges serve as pathways for magma to rise through discontinuities in the oceanic crust, resulting in the formation of new rocks that eventually become part of the oceanic crust.
The relatively thin oceanic crust has long intrigued geologists because it is a potential passageway to rocks that lie in the mantle. Now a team of scientists is undertaking the ambitious task of drilling a hole in the ocean floor to collect samples of intact mantle rock that has not been exposed to the elements.
To date, scientists have made significant progress in reaching mantle rocks that have never undergone the process of melting and subsequent cooling to form the igneous rocks found in the oceanic crust. However, even at these depths, the rocks still show signs of weathering by seawater. This suggests that further excavations are needed to get to the elusive core and unlock its secrets.
Exploring the ocean floor is of great scientific importance, shedding light on the geologic history of the Earth and allowing us to understand the processes that shape our planet. As we continue to delve into the depths of the ocean, we are sure to uncover new secrets and expand our understanding of this mysterious realm.
