Читать книгу Geology For Dummies - Alecia M. Spooner - Страница 72

In 1909, Andrija Mohorovičić, a Croatian seismologist, noticed that earthquake waves increased their speed as they moved through the lower part of the earth’s rigid lithosphere. He interpreted (correctly) that this meant the lower portion of Earth’s lithosphere is made of a different and slightly denser material than the outer portion. The line where the material in Earth’s lithosphere changes from the crustal rock to the mantle rock is named the Moho line or the Mohorovičić Discontinuity.

For decades scientists have attempted drilling deep into the earth, seeking to reach the Moho line between the mantle rock and crustal rock within the lithosphere. In 2005, a team of scientists with the Integrated Ocean Drilling Program (IODP) came close. The core they drilled near the mid-Atlantic ridge in the Atlantic Ocean reached a depth of 1,416 meters (4,644 feet) into the oceanic crust. But the rocks they recovered appear to be made of crustal rock materials rather than the mantle rocks they were seeking. The researchers concluded that they were close to crossing the Moho discontinuity boundary and plan to attempt drilling a new hole.

Every inch closer to the Moho provides scientists with new information about the composition and formation of the earth’s outermost layer and offers clues to the internal structure of Earth’s lithosphere.