Journey To The Center Of The Earth 

Moho (Mohorovičić Discontinuity)

 

               Moho is the second closest layer to us, the crust being the closest layer. Moho is the layer beneath the crust and right on top of the mantle. Moho is also considered the base of the crust. Underneath the ocean the moho is usually around 3 miles thick; underneath continents the moho can be upto 25 miles thick. Moho is sort for Mohorovičić Discontinuity coming from the name of the creator Andrija Mohorovičić. The first known use or knowledge of the Mohorovičić Discontinuity was in 1952 (62 years ago!). Even though technology has advanced immensely, it is still difficult to study the moho. Geologists use two main methods, seismic and gravimetric. 

 

                 Seismic means of or relating to earthquakes or other vibrations of the earth and it's crust. Relating to or denoting geological surveying methods involving vibrations produced artificially by explosions. Gravimetric means of or relating to the measurementof weight or gravity. Mohorovičić discovered the moho using seismic waves. Mohorovičić used the seismic waves to see how they change their speed and direction as they move from one layer of the earth to the next. The waves changes because the properties of the rock the waves are traveling through change. Very much like how if light passses through a crystal the light changes colors and direction. Gravimetry looks at the gravitational effect that the rock under different parts of the earth have due to their differing densities that in turn are a result of different rock compositions.