Quiz on Igneous Rocks

What are rocks made of?

• Water and air

• One or more minerals

• Sand and soil

• Plants and animals

Answer explanation

Rocks are primarily composed of one or more minerals, which are naturally occurring solid substances. Other options like water, air, sand, soil, plants, and animals do not define the fundamental composition of rocks.

How are igneous rocks formed?

• By the accumulation of sand

• From molten rock cooling

• Through plant decay

• By water evaporation

Answer explanation

Igneous rocks are formed from molten rock, known as magma, that cools and solidifies. This process can occur either beneath the Earth's surface or after volcanic eruptions, making 'From molten rock cooling' the correct choice.

Where do intrusive igneous rocks form?

• On the ocean floor

• On Earth's surface

• Beneath Earth's surface

• In the atmosphere

Answer explanation

Intrusive igneous rocks form beneath Earth's surface as magma cools slowly, allowing large crystals to develop. This distinguishes them from extrusive rocks, which form on the surface.

What is a characteristic of extrusive igneous rocks?

• Large, visible crystals

• Coarse texture

• Small, no visible crystals

• Formed from plant material

Answer explanation

Extrusive igneous rocks cool quickly on the Earth's surface, resulting in small or no visible crystals. This contrasts with intrusive igneous rocks, which cool slowly and have large, visible crystals.

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 that cools quickly.

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

• Diorite

• Granite

• Basalt

• Marble

Answer explanation

Basalt is an extrusive igneous rock formed from lava that cools quickly on the Earth's surface. In contrast, diorite and granite are intrusive igneous rocks that cool slowly beneath the surface, while marble is a metamorphic rock.