Eduqas A-level Geology · F3

Time and change

Exam-style questions with answers for F3 Time and change in Eduqas A-level Geology (spec A480QS). Practise with flashcards, a topic quiz, a random quiz across the course, 5 crosswords, or read every question and answer below.

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Question 1 · Spec F3, Key Idea 1 · Uniformitarianism
Explain the principle 'the present is the key to the past'. [2 marks]
Answer:
Processes we can observe today can be used to interpret ancient rocks and environments (1); although rates and conditions may have differed in the past (1).
Question 2 · Spec F3, Key Idea 2 · Geological time
Explain how an angular unconformity provides evidence for a long geological history. [2 marks]
Answer:
It records deposition, lithification, folding, uplift and erosion before renewed deposition (1); at present-day rates these processes take millions of years (1).
Question 3 · Spec F3, Key Idea 2 · Correlation
State William Smith's principle of faunal succession and how it is used. [2 marks]
Answer:
Fossil assemblages succeed one another in a definite, recognisable order (1); so rocks with the same fossils can be correlated between different places (1).
Question 4 · Spec F3, Key Idea 1 · Facies
Distinguish between lithofacies and biofacies. [2 marks]
Answer:
Lithofacies is defined by rock characteristics such as grain size and sedimentary structures (1); biofacies is defined by the fossil assemblage (1).
Question 5 · Spec F3, Key Idea 1 · Palaeoenvironments
Explain why the enclosing sediment should be considered when interpreting a fossil's environment. [2 marks]
Answer:
The fossil's morphology suggests its mode of life (1); but it may have been transported, so the sediment shows the environment where it was buried (1).
Question 6 · Spec F3, Key Idea 1 · Brachiopods and bivalves
Compare the symmetry of brachiopods and bivalves. [2 marks]
Answer:
Brachiopods: the two valves are different, but each valve is bilaterally symmetrical (1); bivalves: the two valves are mirror images, but each valve is asymmetrical (1).
Question 7 · Spec F3, Key Idea 1 · Brachiopods
State the function of the pedicle foramen of a brachiopod. [1 mark]
Answer:
An opening for the fleshy pedicle, which attached the animal to the sea floor.
Question 8 · Spec F3, Key Idea 1 · Bivalves
State four features used to describe a bivalve shell. [4 marks]
Answer:
Any four from: umbo (1); hinge line with teeth and sockets (1); muscle scars (1); pallial line (1); pallial sinus (1); growth lines (1).
Question 9 · Spec F3, Key Idea 1 · Bivalves
Explain how a deep pallial sinus shows a bivalve was a burrower. [2 marks]
Answer:
It shows the animal had large siphons that could be retracted into the shell (1); allowing it to stay buried while drawing in water from above (1).
Question 10 · Spec F3, Key Idea 1 · Bivalves
State two pieces of shell evidence that a bivalve lived attached to a surface. [2 marks]
Answer:
Any two from: a byssal gape or notch for byssal threads (1); one valve cemented and irregular in shape (1); a flattened attachment area (1).
Question 11 · Spec F3, Key Idea 1 · Cephalopods
State two features used to recognise a fossil cephalopod. [2 marks]
Answer:
A shell divided into chambers by septa (1); suture lines visible where the septa meet the shell wall (1).
Question 12 · Spec F3, Key Idea 1 · Cephalopods
Describe the differences between goniatitic, ceratitic and ammonitic sutures. [3 marks]
Answer:
Goniatitic: simple, smooth zigzag lobes and saddles (1); ceratitic: smooth saddles with frilled lobes (1); ammonitic: highly frilled lobes and saddles (1).
Question 13 · Spec F3, Key Idea 1 · Corals
State two features used to identify a fossil coral. [2 marks]
Answer:
Radial septa within the corallite (1); whether it is solitary or colonial (1).
Question 14 · Spec F3, Key Idea 1 · Trilobites
Name the three main parts of a trilobite. [3 marks]
Answer:
Cephalon (head) (1); thorax (1); pygidium (tail) (1).
Question 15 · Spec F3, Key Idea 1 · Trilobites
Explain why segment counts and spine positions are used in trilobite identification keys. [2 marks]
Answer:
They are clearly observable features (1); that differ between species, so they separate one taxon from another (1).
Question 16 · Spec F3, Key Idea 1 · Trilobites
Describe morphological features that suggest a trilobite was pelagic rather than benthic. [2 marks]
Answer:
Large, all-round eyes (1); a small, streamlined or inflated body, rather than a flattened form with small eyes (1).
Question 17 · Spec F3, Key Idea 1 · Graptolites
Define the terms 'stipe' and 'theca'. [2 marks]
Answer:
A stipe is a branch of the graptolite colony (1); a theca is a cup on the stipe that housed an individual zooid (1).
Question 18 · Spec F3, Key Idea 2 · Graptolites
Explain why graptolites are useful for dating Early Palaeozoic rocks. [2 marks]
Answer:
They evolved rapidly, changing in stipe number and thecal shape (1); so each species had a short time range, defining biozones (1).
Question 19 · Spec F3, Key Idea 1 · Plant fossils
State which plant fossil gives the best evidence for a local land surface, and why. [2 marks]
Answer:
Roots preserved in growth position (1); because they have not been transported, unlike isolated leaves or stems (1).
Question 20 · Spec F3, Key Idea 1 · Trace fossils
Distinguish between a trace fossil and a body fossil. [2 marks]
Answer:
A trace fossil records an organism's activity, such as a burrow or footprint (1); a body fossil preserves part of the organism itself, such as a shell (1).
Question 21 · Spec F3, Key Idea 1 · Trace fossils
Explain why burrows are better environmental evidence than transported shells. [2 marks]
Answer:
Burrows are formed in place and cannot be transported (1); so they show organisms were living in that sediment (1).
Question 22 · Spec F3, Key Idea 1 · Preservation
Define the terms 'silicification' and 'pyritisation'. [2 marks]
Answer:
The original fossil material is replaced by silica (1); or by pyrite, keeping the shape of the organism (1).
Question 23 · Spec F3, Key Idea 1 · Preservation
Distinguish between an external mould and a cast. [2 marks]
Answer:
An external mould is an impression of the outside of the shell left after it dissolves (1); a cast forms when the mould is filled with sediment or minerals (1).
Question 24 · Spec F3, Key Idea 1 · Preservation
Describe how carbonisation preserves plants. [2 marks]
Answer:
Volatile compounds are driven off during burial (1); leaving a thin film of carbon that shows the outline of the plant (1).
Question 25 · Spec F3, Key Idea 1 · Assemblages
State two features of a life assemblage. [2 marks]
Answer:
Any two from: fossils in their life positions (1); articulated shells (1); a range of sizes and ages (1); delicate structures preserved (1).
Question 26 · Spec F3, Key Idea 1 · Assemblages
Explain why a death assemblage may contain fossils from different habitats. [2 marks]
Answer:
Dead organisms were transported and mixed before burial (1); so the assemblage reflects sorting by currents as well as the original ecology (1).
Question 27 · Spec F3, Key Idea 1 · Derived fossils
A Jurassic fossil occurs in a pebble in a Cretaceous conglomerate. Explain what this shows. [2 marks]
Answer:
The fossil is a derived (reworked) fossil (1); it dates the source rock of the pebble, not the conglomerate (1).
Question 28 · Spec F3, Key Idea 1 · Preservation
Explain why hard-bodied marine organisms are common in the fossil record. [2 marks]
Answer:
Hard parts resist decay and scavenging (1); and marine environments have continuous sedimentation, allowing rapid burial (1).
Question 29 · Spec F3, Key Idea 1 · Preservation
State three processes that destroy fossils. [3 marks]
Answer:
Any three from: weathering and erosion (1); metamorphism (1); bacterial decay (1); scavenging (1); dissolution during diagenesis (1).
Question 30 · Spec F3, Key Idea 1 · Fossil data
Explain why sample size must be considered when comparing fossil abundance. [2 marks]
Answer:
A larger volume of rock is likely to contain more fossils (1); so counts must be standardised, e.g. per kg of rock, for a fair comparison (1).
Question 31 · Spec F3, Key Idea 1 · Statistics
Name the statistical test used to compare two independent samples of fossil lengths that are not normally distributed. [1 mark]
Answer:
The Mann-Whitney U test.
Question 32 · Spec F3, Key Idea 1 · Assemblages
One fossil sample is more broken and size-sorted than another. Suggest an explanation. [2 marks]
Answer:
It has been transported further or reworked by stronger currents (1); breaking shells and sorting them by size (1).
Question 33 · Spec F3, Key Idea 2 · Relative dating
State the principle of superposition. [2 marks]
Answer:
In an undisturbed sequence, the oldest beds are at the bottom and the youngest at the top (1); provided the beds have not been overturned (1).
Question 34 · Spec F3, Key Idea 2 · Relative dating
A dyke cuts sandstone and shale. State which is youngest and name the principle used. [2 marks]
Answer:
The dyke is youngest (1); the principle of cross-cutting relationships (1).
Question 35 · Spec F3, Key Idea 2 · Relative dating
Granite contains fragments of the surrounding schist. State the relative ages and name the principle. [2 marks]
Answer:
The schist is older than the granite (1); the principle of included fragments (xenoliths) (1).
Question 36 · Spec F3, Key Idea 2 · Way up
Explain how graded bedding can show whether beds are the right way up. [2 marks]
Answer:
Grain size decreases upwards from a coarse base in an upright bed (1); if the coarse grains are at the top, the beds have been overturned (1).
Question 37 · Spec F3, Key Idea 2 · Unconformities
State the events that must have happened before younger beds were deposited across an angular unconformity. [3 marks]
Answer:
Deposition and lithification of the older beds (1); folding or tilting (1); uplift and erosion (1).
Question 38 · Spec F3, Key Idea 2 · Radiometric dating
Define the term 'half-life'. [1 mark]
Answer:
The time taken for half the parent atoms in a sample to decay.
Question 39 · Spec F3, Key Idea 2 · Radiometric dating
A mineral retains 25% of its parent isotope. How many half-lives have passed? [1 mark]
Answer:
Two half-lives (100% → 50% → 25%).
Question 40 · Spec F3, Key Idea 2 · Radiometric dating
A mineral retains one-eighth of its parent isotope. The half-life is 400 Ma. Calculate its age. [2 marks]
Answer:
One-eighth remaining = 3 half-lives (1); 3 × 400 = 1200 Ma (1).
Question 41 · Spec F3, Key Idea 2 · Radiometric dating
Explain why loss of the daughter isotope gives an age that is too young. [2 marks]
Answer:
The age is calculated from the ratio of daughter to parent (1); so less daughter makes it seem that less time has passed (1).
Question 42 · Spec F3, Key Idea 2 · Radiometric dating
Explain why potassium-argon dating records the time an igneous rock cooled. [2 marks]
Answer:
Argon is a gas that escapes while the rock is molten or hot (1); once cooled, argon from decay is trapped, so the clock starts (1).
Question 43 · Spec F3, Key Idea 2 · Radiometric dating
Name the parent and daughter isotopes in samarium-neodymium dating. [2 marks]
Answer:
Parent: samarium-147 (1); daughter: neodymium-143 (1).
Question 44 · Spec F3, Key Idea 2 · Radiometric dating
Explain why a detrital grain in a sandstone may give an older age than the sandstone. [2 marks]
Answer:
The grain crystallised in an older source rock (1); before it was weathered, transported and deposited (1).
Question 45 · Spec F3, Key Idea 2 · Zone fossils
State four features of a good zone fossil. [4 marks]
Answer:
Any four from: short time range (rapid evolution) (1); wide geographical distribution (1); abundant (1); easily recognised (1); found in many facies (1); readily preserved (1).
Question 46 · Spec F3, Key Idea 2 · Zone fossils
Explain why a planktonic fossil is more useful for correlation than a bottom-dwelling one. [2 marks]
Answer:
Plankton drifted widely and are found in many sedimentary environments (1); a bottom-dweller may be absent because conditions were unsuitable, not because of age (1).
Question 47 · Spec F3, Key Idea 2 · Range charts
Fossil A ranges from 140 to 130 Ma and fossil B from 135 to 125 Ma. State the age of a bed containing both. [1 mark]
Answer:
135–130 Ma (the overlap of the ranges).
Question 48 · Spec F3, Key Idea 2 · Geological column
Explain how relative and absolute dating complement each other. [2 marks]
Answer:
Relative dating puts rocks and events in order (1); radiometric dating gives numerical ages to calibrate the geological column (1).
Question 49 · Spec F3, Key Idea 1 · Uniformitarianism
Explain how uniformitarianism can include catastrophic events. [2 marks]
Answer:
Rapid events such as eruptions, floods and impacts happen today (1); so the rock record shows slow change punctuated by short catastrophic events (1).
Question 50 · Spec F3, Key Idea 1 · Fossil drawings
State three features that make a fossil drawing useful scientific evidence. [3 marks]
Answer:
Accurate proportions with diagnostic features shown (1); clear labels (1); a scale or magnification (1).

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Time and change

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