Exploring Igneous Rocks and Their Properties 3.2

This rock was molten magma that slowly cooled under the ground. What type of rock is this?

• Sedimentary

• Igneous

• Metamorphic

Answer explanation

The rock described is igneous because it formed from molten magma that cooled slowly underground. This process leads to the formation of intrusive igneous rocks, distinguishing them from sedimentary and metamorphic rocks.

Tags

NGSS.MS-ESS2-1

What the name of a rock composed of K feldspar, quartz, plagioclase feldspar, biotite, and amphobole with glassy texture?

• Basalt

• Obsidian

• Pumice

• Rhyolite

Answer explanation

Obsidian is a volcanic glass that can contain minerals like K feldspar, quartz, and biotite, giving it a glassy texture. The other options, like basalt and pumice, do not match this mineral composition or texture.

Tags

NGSS.MS-ESS2-3

NGSS.MS-PS1-1

Rhyolite is a fine-grained, extrusive, igneous rock. How did it form?

• rapidly cooling lava

• slowly cooling magma

Answer explanation

Rhyolite forms from rapidly cooling lava that erupts at the surface. This quick cooling prevents large crystals from forming, resulting in its fine-grained texture, distinguishing it from rocks formed from slowly cooling magma.

How does the temperature of extrusive rock compare to the temperature of intrusive rock?

• extrusive rock cools more slowly

• intrusive rock cools more slowly

• both cool at the same rate

Answer explanation

Intrusive rock cools more slowly than extrusive rock because it forms from magma that cools beneath the Earth's surface, allowing for larger crystal formation. In contrast, extrusive rock cools quickly on the surface.

Tags

NGSS.MS-PS1-4

NGSS.MS-PS3-4

Which process is primarily responsible for the formation of igneous rocks?

• Sedimentation

• Melting and solidification of magma or lava

• Metamorphism

• Erosion

Answer explanation

Igneous rocks form primarily through the melting and solidification of magma or lava. This process involves the cooling of molten rock, which crystallizes to create various types of igneous rocks.

What are the two main types of igneous rocks?

• Sedimentary and Metamorphic

• Intrusive and Extrusive

• Foliated and Non-foliated

• Clastic and Chemical

Answer explanation

The two main types of igneous rocks are Intrusive and Extrusive. Intrusive rocks form from magma that cools slowly beneath the Earth's surface, while Extrusive rocks form from lava that cools quickly on the surface.

Which mineral is most commonly found in igneous rocks?

• Quartz

• Halite

• Gypsum

• Calcite

Answer explanation

Quartz is the most abundant mineral in igneous rocks, forming from the cooling and solidification of magma. In contrast, halite, gypsum, and calcite are more commonly associated with sedimentary environments.

How does the cooling rate of magma affect the texture of igneous rocks?

• Faster cooling results in larger crystals

• Slower cooling results in smaller crystals

• Faster cooling results in smaller crystals

• Cooling rate has no effect on crystal size

Answer explanation

Faster cooling of magma leads to smaller crystals because there is less time for the crystals to grow. In contrast, slower cooling allows more time for larger crystals to form.

What is the primary difference between intrusive and extrusive igneous rocks?

• Intrusive rocks form on the Earth's surface, while extrusive rocks form below the surface

• Intrusive rocks form below the Earth's surface, while extrusive rocks form on the surface

• Intrusive rocks are always darker in color than extrusive rocks

• Intrusive rocks are always lighter in color than extrusive rocks

Answer explanation

The primary difference is that intrusive rocks form below the Earth's surface, allowing slow crystallization, while extrusive rocks form on the surface from lava that cools quickly.

Which of the following is an example of an intrusive igneous rock?

• Basalt

• Granite

• Pumice

• Obsidian

Answer explanation

Granite is an intrusive igneous rock formed from magma that cools slowly beneath the Earth's surface, allowing large crystals to develop. In contrast, basalt, pumice, and obsidian are extrusive igneous rocks formed from lava at the surface.