4. Rocks: Prepositional Phrases

Prepositional phrases are versatile.
In scientific writing, the same phrase can play two different roles depending on whether it is “sticking” to a noun or “explaining” a verb.
  • As a Qualifier (part of the Noun Group)
    It describes a noun and tells us which specific thing we are talking about.
    It cannot be moved away from the noun without breaking the meaning.
    • Example: The crystals in the sedimentary layer are microscopic.

    • Scientific Logic: (Qualifier — which crystals? Only the ones in that specific layer.)

  • As a Circumstance (part of the Clause)
    It describes a process (verb) and tells us where, when, or how the action happened.
    These phrases are more mobile and can often be moved to the start of the sentence.
    • Example: The crystals formed in the sedimentary layer.

    • Scientific Logic: (Circumstance — where did the process of ‘forming’ occur?)


Multiple-Choice Questions

Choose the best answer for each question.

In the sentence below, what is the function of the prepositional phrase “in the cave”?

The crystals in the cave were unusually large.

a. Qualifier
b. Circumstance

In the sentence below, what is the function of the prepositional phrase “in the cave”?

New crystals formed in the cave over thousands of years.

a. Qualifier
b. Circumstance

What is the function of the prepositional phrase “under the crust”?

The pressure under the crust increases with depth.

a. Qualifier
b. Circumstance

What is the function of the prepositional phrase “under the crust”?

Pressure increases under the crust during tectonic movement.

a. Qualifier
b. Circumstance

What is the function of the prepositional phrase “between the layers”?

The minerals between the layers act as cement.

a. Qualifier
b. Circumstance

What is the function of the prepositional phrase “between the layers”?

New crystals grow tightly between the layers.

a. Qualifier
b. Circumstance

What is the function of the prepositional phrase “along the coastline”?

The erosion along the coastline is increasing.

a. Qualifier
b. Circumstance

What is the function of the prepositional phrase “along the coastline”?

Large rocks break down quickly along the coastline.

a. Qualifier
b. Circumstance

What is the function of the prepositional phrase “with large grains”?

The igneous rocks with large grains are intrusive.

a. Qualifier
b. Circumstance

What is the function of the prepositional phrase “with large grains”?

Magma solidifies with large grains when cooling is slow.

a. Qualifier
b. Circumstance