Why are we drilling into the Earth? Earth Day special

On April 12, 2023, geologists, microbiologists and other scientists will sail to the Atlantis Massif, a 14,000-foot underwater mountain sitting on the floor of the Atlantic Ocean. The plan: To dig into an already existing 4,640-foot hole drilled nearly 20 years ago to 6,750 feet.

The hole will not be the deepest but will take us closer than ever to the Earth’s mantle. At such depths, temperatures are expected to cross 204 degrees Celsius. Such expeditions are currently underway all across the world.

All in the quest to uncover clues to how our planet evolved over millennia and how life began.

In the early 1960s, a group of scientists flagged off “Project Mohole”. It aimed to drill a hole (Mexico) through the core to reach the boundary between the crust and mantle called Mohorovičić Discontinuity or Moho, in short. Oceanic crusts are thinner than their continental counterparts. So, the sea route was a natural choice. This expedition was crucial in demonstrating that drilling was technologically possible. But due to a lack of funding the project was dissolved.
In 1989, a Russian project in the Kola peninsula drilled 12.2 km into the earth’s crust — the deepest hole dug so far. The rocks extracted from it at a depth of about 3 km were almost identical to lunar soil. At 10 km depth, the team found petrified remains of ancient living organisms.

Scientists rely on seismic waves — shockwaves generated after an earthquake — to peer into the world below. These waves behave differently when passed through different materials and are picked up by sensitive instruments called seismometers.

Researchers also study volcanic rocks made up of magnetic materials, which document the Earth’s past magnetic field. This magnetic field acts as a protective bubble and keeps the harmful solar wind from stripping our ozone layer and atmosphere. Without the magnetic field, our planet would look like Mars.

The core and the mantle also release heat. This internal heat powers the tectonic plates that comprise the Earth’s crust and the uppermost part of the mantle. Plates move about 5 cm per year. Movements between these plates built the landscapes we see on the planet. They can cause the land to rise, leading to the formation of mountains, which in turn, can alter the motion of air. Volcanoes, which form at the boundaries of tectonic plates, regulate atmospheric greenhouse gas concentrations and surface temperatures by releasing carbon dioxide into the atmosphere and returning the gas to the earth’s interior at subduction zones, where a tectonic plate sinks below the adjoining one. This cycle is also believed to have created the atmosphere, oceans, and continents and the conditions suitable for life.

So, all these earthquakes, volcanic eruptions, microbial life, past climate, and the planet’s evolution can be studied by scientists through such drilling experiments on land and the seafloor.

g. In 2016, researchers from the Union Ministry of Earth Sciences drilled into a seismically active region Koyna, located on India’s west coast. The idea was to understand why the region, which was not prone to earthquakes until the 1960s, had suddenly become seismically active. Scientists assumed that impounding of the Shivajisagar Lake in 1962 was responsible for Koyna’s seismicity. They collected cylindrical rock samples — 9 meters long and 4 inches wide. The team plan to conduct further analysis to unpack the mechanisms driving the seismicity.

They also plan to place seismometers inside the borehole. Typically, earthquakes occur at depths of two and 10 kilometers. Placing instruments at these levels can help scientists follow the seismic activity more closely. It also cuts off disturbances from other sources, such as basalt rocks and generates a clean record. Small-magnitude earthquakes are also detected with greater accuracy.

India has also been active in the ocean drilling space. In 2009, the Union Ministry of Earth Sciences joined the International Ocean Discovery Program, an international consortium on ocean research that explores Earth's history and dynamics.

In 2015, an expedition led by an Indian researcher (Dhananjay Pandey) spent about 60 days drilling two holes in the Lakshmi basin of the Arabian Sea. The team reached depths of 1.1 km below the sea floor in 3.6 km deep water. The motive was to collect samples and investigate when the South Asian monsoon intensified.

So far, the 12.2 km record has not been broken. But scientists are determined to get deeper because understanding the past is important to understand where we are heading.

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