Question

As new land is formed at layer A from magma that breaks through the surface of the Earth and cools, what type of rock

would be predominantly generated?
A)
Sedimentary rock, as it will cover old landscapes
ing
11
ols
B)
Metamorphic rock, as it changes from magma to lava to rock
o
Igneous rock, as molten magma and lava cools to form new land
D)
Intrusive rock, as it breaks free from the inner mantle to the outer mantle

Answer 1

Answer: C

Explanation: Igneous rocks (derived from the Latin word for fire) are formed when molten hot material cools and solidifies. Igneous rocks can also be made a couple of different ways. When they are formed inside of the earth, they are called intrusive, or plutonic, igneous rocks. If they are formed outside or on top of Earth’s crust, they are called extrusive, or volcanic, igneous rocks.

Granite and diorite are examples of common intrusive rocks. They have a coarse texture with large mineral grains, indicating that they spent thousands or millions of years cooling down inside the earth, a time course that allowed large mineral crystals to grow.

Alternatively, rocks like basalt and obsidian have very small grains and a relatively fine texture. This happens because when magma erupts into lava, it cools more quickly than it would if it stayed inside the earth, giving crystals less time to form. Obsidian cools into volcanic glass so quickly when ejected that the grains are impossible to see with the naked eye.

Extrusive igneous rocks can also have a vesicular, or “holey” texture. This happens when the ejected magma still has gases inside of it so when it cools, the gas bubbles are trapped and end up giving the rock a bubbly texture. An example of this would be pumice.