Question 1 of 21: Question 1, Part 1: Multiple Choice

Question 1, Part 1: Multiple Choice (6 marks)

Question text not reproduced: the examination questions are © Engineers and Geoscientists BC. Open the official past paper (linked at the top of this page) to read the question, then follow the worked solution below.

1) → (c) a few metres. Coseismic slip recorded on major faults during large earthquakes is typically metres, occasionally reaching several metres to a few tens of metres for great events (e.g. ~6 m during the 1906 San Francisco earthquake) – far below "kilometres" and far above imperceptible millimetre creep.

2) → (c) compression, shear, and tension. These are the three fundamental differential-stress states applied to rock: compression shortens, tension stretches, and shear offsets rock parallel to a surface; hydrostatic/lithostatic stress (option b) is by definition non-differential (equal in all directions).

3) → (a) folded anticlines and synclines. Compressive orogenic stress bends originally flat-lying strata into up-arched (anticline) and down-arched (syncline) folds; horsts and grabens (option c) are extensional fault-bounded blocks, not folds.

4) → (d) along plate margins. Nearly all significant crustal strain (seismicity, folding, faulting) concentrates at convergent, divergent, and transform plate boundaries, not in stable plate interiors (cratons) or passive sedimentary basin fill.

5) → (a). Explosive eruptions occur when dissolved volatiles (H&sub2;O, CO&sub2;) come out of solution as pressure drops, forming bubbles that violently lower the magma's bulk density and propel it (and pulverized rock) from the vent – the process most pronounced in viscous, silica-rich, gas-charged magmas.

6) → (b) erosion of overlying rocks due to uplift. Plutons crystallize kilometres underground; regional uplift followed by prolonged erosion of the overlying rock (often tens of millions of years later) exhumes them at the surface – there is no "igneous inversion" or violent upheaval mechanism.