Types of Rocks

Which layer of the Earth is most similar to the skin of a peach?

• Core

• Mantle

• Crust (Lithosphere)

• Hydrosphere

Answer explanation

The Earth's crust (lithosphere) is the outermost layer, similar to the skin of a peach, as it is thin and covers the underlying layers, just like peach skin encases the fruit.

Metamorphic rocks are formed through:

• Melting completely

• Intense heat and pressure without full melting

• Ocean water deposition

• Volcanic eruptions

Answer explanation

Metamorphic rocks are formed through intense heat and pressure that alter existing rocks without completely melting them. This process distinguishes them from igneous rocks, which form from melting.

If limestone transforms under extreme conditions, it becomes:

• Sandstone

• Slate

• Marble

• Quartzite

Answer explanation

Limestone transforms into marble under extreme heat and pressure, a process known as metamorphism. This makes marble the correct answer, while sandstone, slate, and quartzite are formed from different processes.

Which rock type is considered "Nature's Record Keeper"?

• Igneous rocks

• Metamorphic rocks

• Sedimentary rocks

• Volcanic rocks

Answer explanation

Sedimentary rocks are known as "Nature's Record Keeper" because they form from the accumulation of sediments, preserving evidence of past environments, life forms, and geological events, unlike igneous or metamorphic rocks.

Rocks that form deep within Earth's crust are classified as:

• Extrusive rocks

• Intrusive rocks

• Surface rocks

• Sedimentary rocks

Answer explanation

Rocks that form deep within Earth's crust cool slowly, allowing large crystals to form. These are classified as intrusive rocks, unlike extrusive rocks, which form from lava on the surface.

The lithosphere specifically includes:

• Ocean water

• Atmospheric gases

• Continents and rocky ocean beds

• Molten magma

Answer explanation

The lithosphere includes the rigid outer layer of the Earth, which consists of the continents and rocky ocean beds. Ocean water and atmospheric gases are not part of the lithosphere, and molten magma is found beneath it.

Which statement best describes why rocks are crucial to human life?

• They are decorative

• They provide minerals and raw materials

• They are always colourful

• They are lightweight

Answer explanation

Rocks are essential because they provide minerals and raw materials that are vital for various human activities, including construction, manufacturing, and agriculture, making them crucial for sustaining life.

Extrusive rocks are formed:

• Deep underground

• At or near Earth's surface

• In laboratory conditions

• Underwater

Answer explanation

Extrusive rocks are formed at or near Earth's surface when magma erupts and cools quickly, solidifying into rock. This distinguishes them from intrusive rocks, which form deep underground.

A scientist studying rocks to understand geological history would be most interested in:

• Their colour

• Their weight

• Their formation process

• Their texture

Answer explanation

The formation process of rocks reveals their history and the conditions under which they were created, making it crucial for understanding geological history. Other factors like color, weight, and texture are less significant in this context.

Which of the following is NOT a primary rock type?

• Igneous

• Sedimentary

• Volcanic

• Metamorphic

Answer explanation

Volcanic is not a primary rock type; it refers to a specific type of igneous rock formed from lava. The primary rock types are igneous, sedimentary, and metamorphic.