Free Introduction to Geology Practice Questions

Sample Practice Questions

Try these 10 sample questions from the Introduction to Geology practice bank. Each includes the answer and explanation. Continue with the interactive practice above to review the full question set.

1. 1Which statement correctly describes the relationship between rocks and minerals?

   1. A.Every rock contains several different minerals.
   2. B.A mineral is an aggregate of one or more rocks.
   3. C.A rock is an aggregate of one or more minerals.Correct answer: C
   4. D.Every rock consists of exactly one mineral.

   Explanation: USGS states, "A rock is an aggregate of one or more minerals, or a body of undifferentiated mineral matter." Rocks can consist of one mineral or several, while minerals are not aggregates of rocks.

   Reference: What is the difference between a rock and a mineral? — Minerals, answer

2. 2Which statement correctly distinguishes mechanical from chemical weathering?

   1. A.Both processes must change mineral chemistry.
   2. B.Chemical weathering breaks rock only without altering minerals.
   3. C.Mechanical weathering breaks rock without changing mineral chemistry.Correct answer: C
   4. D.Mechanical weathering changes mineral chemistry without breaking rock.

   Explanation: NPS states, "Mechanical weathering involves physically breaking rocks into fragments without changing the chemical make-up of the individual minerals that make up the rock." Chemical weathering changes minerals and weathering occurs in place.

   Reference: Weathering — Mechanical or Physical Weathering

3. 3An undisturbed lava flow lies between two sedimentary beds. How does its age compare with those beds?

   1. A.Younger than the lower bed and older than the upper bedCorrect answer: A
   2. B.Older than both beds
   3. C.Younger than both beds
   4. D.Older than the lower bed and younger than the upper bed

   Explanation: USGS says a flow obeying superposition "is younger than the beds below it and older than the beds above it." The other options reverse one or both age relationships.

   Reference: Fossils, Rocks, and Time: The Laws of Superposition and Cross-Cutting Relations — The Laws of Superposition and Cross-Cutting Relations

4. 4A natural deposit contains minerals that can be extracted for economic value. What is the material mined for those minerals called?

   1. A.OreCorrect answer: A
   2. B.Overburden
   3. C.Tailings
   4. D.Waste rock

   Explanation: USGS defines ore as "The naturally occurring material from which a mineral or minerals of economic value can be extracted." Overburden, waste rock, and tailings are other materials associated with extraction.

   Reference: EarthWord – Ore — Definition

5. 5Which mineral property describes resistance to being scratched?

   1. A.Streak
   2. B.Cleavage
   3. C.HardnessCorrect answer: C
   4. D.Luster

   Explanation: The National Park Service defines hardness as "A measure of a mineral's resistance to scratching." Streak is powder color, cleavage describes preferred breaking, and luster describes reflected light.

   Reference: Minerals — Physical Properties

6. 6Water freezes and expands inside cracks in a rock. What kind of process is this?

   1. A.Chemical weathering
   2. B.Mechanical weatheringCorrect answer: B
   3. C.Sediment transport
   4. D.Sediment deposition

   Explanation: NPS includes "water in cracks freezing and expanding" among mechanical weathering processes. It physically breaks material rather than requiring mineral chemical change.

   Reference: Weathering — Mechanical or Physical Weathering

7. 7A dike cuts through a rock layer. What relative-age relationship follows from cross-cutting relations?

   1. A.The dike is older than the layer it cuts.
   2. B.The dike is younger than the layer it cuts.Correct answer: B
   3. C.The dike and the layer must be the same age.
   4. D.Their relative ages cannot be inferred from the cross-cutting relation.

   Explanation: USGS says, "The dike is younger than all the rocks that it cuts across" and older than uncut rocks above it. The intrusion must follow the formation of the rock it cuts.

   Reference: Fossils, Rocks, and Time: The Laws of Superposition and Cross-Cutting Relations — The Laws of Superposition and Cross-Cutting Relations

8. 8What distinguishes an identified mineral resource from one that is undiscovered?

   1. A.Direct geological evidence verifies the identified resource.Correct answer: A
   2. B.The identified resource must already have been completely mined.
   3. C.The undiscovered resource must already have been drilled.
   4. D.The undiscovered resource must be profitable under today's conditions.

   Explanation: USGS states, "Identified resources are verified using direct geologic evidence, such as drilling into the deposit." Undiscovered resources are instead expected from geological knowledge.

   Reference: From Maybe to Mineable: terms to describe mineral resources and reserves — Detailed Description

9. 9A mineral repeatedly breaks along flat planes of weakness. Which property does this demonstrate?

   1. A.CleavageCorrect answer: A
   2. B.Specific gravity
   3. C.Streak
   4. D.Luster

   Explanation: The National Park Service defines cleavage as "The tendency of a mineral to break (cleave) along weak planes." Specific gravity compares density with water, streak concerns powder color, and luster concerns reflected light.

   Reference: Minerals — Physical Properties

10. 10Which weathering process chemically removes soluble minerals from bedrock and carries them in water?

    1. A.Abrasion
    2. B.DissolutionCorrect answer: B
    3. C.Frost wedging
    4. D.Oxidation

    Explanation: NPS describes dissolution as a process in which "the combination of water and acid slowly removes mineral compounds from solid bedrock and carries them away in liquid solution." Abrasion and frost wedging break rock physically; oxidation is chemical alteration by oxygen.

    Reference: Weathering — Dissolution