1. Earth’s crust is made of rock, so why don’t we see solid rock everywhere on the surface? 2. When can’t we see the crystals in rocks? 3. List four ways that minerals can form. 4. What is the...

1. Earth’s crust is made of rock, so why don’t we see solid rock everywhere on the surface?

2. When can’t we see the crystals in rocks?

3. List four ways that minerals can form.

4. What is the difference between extrusive and intrusive igneous rocks?

5. Why are most igneous rocks very hard?