The Mohorovicic Discontinuity, or Moho, is the boundary between Earth's crust and mantle. It marks the point at which the seismic waves from earthquakes change speed, indicating a change in the rock type. The Moho is generally located about 5 to 35 kilometers (3 to 22 miles) below Earth's surface, but it can be as deep as 70 kilometers (43 miles) beneath mountain ranges.
The Moho was discovered by Croatian seismologist Andrija Mohorovičić in 1909. He noticed that seismic waves from earthquakes near Zagreb, Croatia, changed speed at a depth of about 50 kilometers (31 miles). This indicated that there was a boundary between two layers of rock, with the upper layer being less dense than the lower layer.
The Moho is thought to be composed of a variety of rocks, including peridotite, gabbro, and basalt. These rocks are denser than the rocks in Earth's crust, which is why seismic waves speed up when they pass through the Moho.
Can Humans Ever Reach the Moho?
Humans have not yet reached the Moho, but there have been a number of attempts. In the 1960s, the United States Geological Survey (USGS) drilled a hole called the Kola Superdeep Borehole in Russia. The hole reached a depth of 12,262 meters (40,230 feet), but it did not reach the Moho.
In recent years, there have been a number of proposals to drill new holes that would reach the Moho. One such proposal is the Japan Trench Deep Drilling Project, which is planning to drill a hole in the Pacific Ocean near Japan. The project aims to reach a depth of 15 kilometers (9 miles), which would be the deepest hole ever drilled.
If humans are able to reach the Moho, it would provide a wealth of information about Earth's interior. Scientists could study the rocks that make up the Moho and learn more about the formation and evolution of Earth. They could also study the processes that occur at the boundary between the crust and mantle, such as earthquakes and volcanic eruptions.
Reaching the Moho would be a major scientific achievement, but it would also be a very challenging and expensive undertaking. It is possible that humans may never reach the Moho, but it is a goal that is worth pursuing.
