The Rock Cycle — Practice · Grade 9 Science

Chapter: Rocks, Landscapes & Water

What this practice covers

By the end of The Rock Cycle you should be able to:

10 questions, multiple choice and written answer, each with a worked explanation.

Vocabulary used: rock cycle, lithification, metamorphism, magma.

Problem 1

Which process turns loose sediments into sedimentary rock over time?
  1. Compaction and cementation
  2. Melting and cooling
  3. Heat and pressure deep underground
  4. Weathering into smaller pieces
Answer and explanation

Compaction and cementation

Layers of sediment are pressed together (compaction) and glued by minerals (cementation) to form sedimentary rock.

Problem 2

What is magma called once it erupts above Earth's surface?
  1. Sediment
  2. Lava
  3. Ore
  4. Cement
Answer and explanation

Lava

Magma is called lava once it erupts above the surface.

Problem 3

Which process directly turns loose sediment into solid sedimentary rock?
  1. Metamorphism
  2. Melting
  3. Lithification (compaction and cementation)
  4. Crystallization from magma
Answer and explanation

Lithification (compaction and cementation)

Lithification — compaction plus cementation — squeezes and glues loose sediment into solid sedimentary rock.

Problem 4

Explain why the rock cycle is usually drawn as a loop with arrows going in many directions instead of a single straight line.
Answer and explanation

Because any rock type can change into any other rock type depending on which process acts on it next, there's no fixed starting or ending point, so a loop with many crossing arrows shows all the possible paths.

Problem 5

A geologist finds a rock that used to be metamorphic but is now found surrounded by cooled, hardened lava-like material. Which process most likely happened to the original rock?
  1. It was compacted and cemented
  2. It melted completely into magma, then cooled and crystallized
  3. It was scratched by a harder mineral
  4. It formed layers from deposited sediment
Answer and explanation

It melted completely into magma, then cooled and crystallized

Since the rock is now found within hardened, once-molten material, the original metamorphic rock must have melted into magma before cooling and crystallizing into new igneous rock.

Problem 6

Trace a path from granite to sandstone without melting. Explain the reasoning in your own words.
Answer and explanation

Granite can become sandstone through weathering, transport, deposition and lithification.

Weathering releases grains; erosion transports them and deposition collects them.

Compaction and cementation turn sediment into sedimentary rock.

Response criteria

  • Use the stated conditions.
  • Show the evidence or calculation.
  • Explain the conclusion and any stated limitation.

Problem 7

What process turns loose sediment into sedimentary rock? Show the reasoning, not just the conclusion.
Hints

No melting is specified.

Answer and explanation

Deposition followed by compaction and/or cementation under suitable conditions.

Problem 8

Can an igneous rock become sedimentary without first becoming metamorphic?
Hints

State what the supplied observations or conditions establish, and separate that from any assumption.

Answer and explanation

Yes. Weathering, erosion, deposition and lithification provide a direct pathway through sediments.

Problem 9

Sand becomes sandstone through burial and grain bindingSand becomes sandstone through burial and grain bindingLoose sedimentBuried and cemented grainsCompaction reduces some pore space; cement binds grains.Deposition alone does not turn every loose deposit into rock.
Original grain-scale models compare loose sediment with a cemented deposit. Cement is shown as a continuous background for visibility, not as a uniform literal mineral in every pore. Grain size and burial load are schematic.
Interpret the supplied visual model. What two processes can distinguish deposited loose sand from lithified sandstone?
Answer and explanation

Compaction can reduce spaces and cementation can bind grains with minerals. Their contribution depends on the deposit; sandstone need not form through one identical sequence or degree of compaction.

Compare loose-grain spaces with the modeled mineral cement around grains. The loading arrow indicates burial stress; it is not an instruction to press sediment by hand.

Compaction can reduce spaces and cementation can bind grains with minerals. Their contribution depends on the deposit; sandstone need not form through one identical sequence or degree of compaction.

Response criteria

  • Read the labeled quantities, reference frame or objects correctly.
  • Explain the relation between the visual evidence and the mechanism.
  • Keep the drawing’s stated assumptions and limits in the conclusion.

Problem 10

A rock contains sand grains cemented together. A student calls cementation the same as cooling molten sand. Distinguish the two pathways and name an observation that could help test the interpretation.
Answer and explanation

Cementation binds deposited grains through mineral precipitation; cooling a melt forms igneous material. Preserved grain boundaries, sedimentary textures and field relationships help test a cemented-sediment interpretation. Melting is not required for sandstone.

Cementation binds deposited grains through mineral precipitation; cooling a melt forms igneous material. Preserved grain boundaries, sedimentary textures and field relationships help test a cemented-sediment interpretation. Melting is not required for sandstone.

Response criteria

  • Use the stated measurements or conditions, with correct units.
  • Connect the result to the physical mechanism or evidence relationship.
  • Identify the assumption, model limit or further evidence requested.

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