USESO Guide: Rock Formation and Processes

Question 1

3 ways magma forms

Answer 1

Decreasing pressure, Addition of volatiles, Heat Transfer

Question 2

Why does a decrease in pressure cause magma to form

Answer 2

due to extreme pressure in the mantle, rock cannot melt, but if pressure is decreased, the rock can thus melt. This is called decompression melting

Question 3

Why does the addition of volatiles cause magma to form

Answer 3

When volatiles, such as water and oxygen, are added to the mantle, it causes the rock to melt at lower temperatures, much like snow and salt. This is called flux melting

Question 5

3 different ways magmatic differentiation occurs

Answer 5

Partial melting, Assimilation, fractional crystalization.

Question 6

How does cross bedding form

Answer 6

Currents of air or water can push sand in one direction, creating a distinct crest pattern in the resulting rock. When the wind switches direction, the crest also switches direction