C2.7: Explaining the rock cycle

Lesson focus: Can you connect particles, rocks and evidence?

Learning objective

Apply rock-cycle knowledge to explain how evidence records more than one process.

Build on earlier learning

Igneous and metamorphic rocks

Check the distinction between metamorphism and melting.

You will be successful when you can…

Separate observation and interpretation.
Correct common process errors.
Order a multi-stage history.
Explain marine and metamorphic evidence together.

KEY VOCABULARY

Words that carry the science

geological history: Sequence of past events inferred from rock evidence.
recrystallisation: Growth or rearrangement of crystals in solid rock.
marine sediment: Material deposited in a sea or ocean.
sequence: Events arranged in time order.
interpretation: Explanation inferred from observations.

BUILD YOUR UNDERSTANDING

Reconstruct a geological history from process–evidence links

01Evidence can record several times

A shell fossil may record marine deposition. Mineral alignment or can record later heat and pressure. Both can occur in one mountain history. A rock’s story in order: (1) sand, mud and shells settle at the bottom of an ancient sea. (2) They are buried and squashed into , with fossils inside. (3) Later, heat and pressure change the rock without melting it (). (4) The rock is pushed up () and worn away until it shows on a mountain.

02Keep process consequences explicit

Transport can round grains; lithification binds sediment; metamorphism alters solid rock; uplift exposes it. Each claim needs a consequence.

03Correct impossible routes

Weathering is breakdown in place, not transport. Metamorphic rock does not require melting. Lava is only one source of igneous rock.

Figure · Evidence can record events from different times. A fossil may indicate marine deposition; recrystallisation or aligned minerals may indicate later heat and pressure. Metamorphism does not require melting.

Animation

The rock cycle

Rocks are slowly changed from one type into another over millions of years. Step through each process.

Step 1 of 7

Deposition, compaction and cementationLayers of sediment settle, are squashed by the layers above and are cemented together.

WORKED EXAMPLE

Explain an ancient seabed in a mountain

A mountain rock contains deformed marine fossils and recrystallised minerals.

Marine fossils support deposition in an ancient sea.
Burial and lithification formed rock.
Later heat and pressure deformed/recrystallised it without complete melting.
Uplift and erosion exposed it in a mountain.

How to make the reasoning visible: The evidence records marine deposition before later metamorphism and uplift.

LEARN BY DOING

Claim repair

Replace each incorrect claim with a process-based explanation.

Incorrect claim	Correction	Evidence	Why
All rocks form from lava	Several pathways exist	Sediments/bands/crystals	Processes differ
Weathering means transport	Breakdown in place	Fragments at source	Erosion transports
Metamorphic rock melts	Rock remains solid	Recrystallisation/banding	Melting makes magma
Fossil means no later change	Later alteration possible	Deformation/recrystallisation	Events occur in sequence

Why can a fossil survive some metamorphism?
Your answer
Why must marine deposition come before mountain uplift?
Your answer
Choose one incorrect claim from the table and correct it.
Your answer

RETRIEVE · APPLY · CHECK

Check your understanding

Answer from memory, then check against the suggested answer.

What is geological history?

What is recrystallisation?

What is marine sediment?

Does metamorphic rock melt when it forms?

What does sequence mean in geology?

Apply the idea

Correct “sedimentary rock becomes metamorphic rock by melting”.

Stretch and challenge

What additional evidence would test the ancient-sea interpretation?

Sea-shell fossils are found high up on a mountain. Explain how they got there.

Exam Question Practice

C2.7Explain5 marks

Exam Question Practice

Mark points shown after marking

A rock high on a mountain has sea-shell fossils in it, and it shows signs of being heated. Answer the parts to explain how this could happen.

(a)

Where did the shells and sediment first settle?

(1)

(b)

What happened to them to make rock?

(1)

(c)

What changed the rock later?

(1)

(d)

Did the rock melt? What is this change called?

(1)

(e)

How did the rock end up on a mountain?

(1)

Total for this question: 5 marks

Command word: Tell the rock’s story in time order, using section 01.