Intrusive igneous rocks form from magma that cools and solidifies inside the Earth

Intrusive igneous rocks form from magma that cools and solidifies inside the Earth. Compositionally, more intrusive igneous rocks are formed in continental crust from intermediate and felsic magmas than mafic magmas. In other words, granite and diorite are more commonly found in continental crust than gabbro. Can you explain why?

Erosion is typically described as an unwanted process that can wreak havoc on building sites, agricultural fields, and be very dangerous along steep slopes. Can you think of any positive results or discoveries that have occurred as a result of erosion?