Which boundary marks a transition from the crust and upper mantle to the deeper mantle layers?

The boundary that marks the transition from the crust and upper mantle to the deeper mantle layers is the Mohorovicic Discontinuity, commonly referred to as the Moho. This discontinuity represents a significant change in the composition and properties of the Earth’s materials. It is located at varying depths from about 5 to 70 kilometers beneath the Earth's surface, separating the less dense, silica-rich rocks of the crust from the denser, magnesium and iron-rich silicate minerals of the upper mantle.

The Moho is critical in understanding the Earth's internal structure because it highlights the transition between different geological layers, which have distinct physical and chemical properties. The characteristics of seismic waves also change at this boundary, providing valuable information about the Earth's interior through seismic studies.

The other choices refer to different boundaries or layers within the Earth. For example, the Gutenberg Discontinuity marks the transition from the mantle to the outer core and is much deeper than the Moho. The Asthenosphere refers to the ductile layer within the upper mantle that lies just below the lithosphere and is important for tectonic movement but does not define the transition from crust to mantle. Finally, the term "Latin Discontinuity" is not recognized in geological terminology, making it