The Moho

Mantle គម្រប់ផែនដី                          crust ស្រទាប់លើគម្រប់ផែនដី

Discontinuity ភាពដាច់គ្នា                  encompasses មាន

seismic waves រលកសេស្មិច                 draw some interesting conclusion ធ្វើសេចក្តីបញ្ចប់ដ៏ចាប់អារម្មណ៍មួយចំនួន

surface elevations កម្ពស់ផ្ទៃផែនដី

The dividing line between the Earth’s mantle and crust is called the Moho, which is short for Mohorovicic discontinuity and is named after the scientist who discovered it. The mantle is the region of the Earth that extends from the outer edge of the core almost to surface; it is 2,900 kilometers thick and encompasses about 84 percent of total volume of the Earth. The crust, on the other hand, is the thin outer layer of the Earth. The term “Moho” is used to indicate where the mantle ends and the crust begins.

Using the reflection of seismic waves at thousands of different locations, scientists have been able to draw some interesting conclusion about the Moho. First of all, the crust is very thin, averaging only about 10 to 20 kilometers in thickness, compared with tens of thousands of kilometers in width. In addition, the Moho varies to a considerable degree in depth and is deepest below the highest mountain ranges and shallower below regions with lower surface elevations. The Moho reaches depths of about 70 kilometers beneath massive mountain ranges, approximately 40 kilometers beneath average continental regions, and only 6 kilometers beneath the ocean floor.

Extracted from the book of LONGMAN Preparation Course for the TOEFL Test and translated by Ty Theavy