Question

Where is the depth of the Sial less ?
1. On land
2. Lower part of mountains
3. Ocean bottom 
4. Same depth everywhere

Answer 1

Correct Answer - Option 1 : On land

In geology, the term sial refers to the composition of the upper layer of Earth's crust, namely rocks rich in aluminium silicate minerals.

SiAl:

• The uppermost layer of the crust is called the SiAl, consisting of silicate and aluminium (Si = silicate, Al = aluminium).
• On average, the thickness of the SiAl is 25 km from the surface. 
• Mountains extend down as well as up, much like icebergs on the ocean; so that on the continental plates, the sial runs between 5 km and 70 km deep.
• SiAl is thick over the continents and very thin or absent on the ocean floor, especially the Pacific Ocean.

Thus, we can conclude that on land the depth of the Sial is less.