OCR A-Level Geology Module 1 fieldwork and geological skills overview quiz quiz

It runs in a perfectly straight line across the map, ignoring all relief

It Vs sharply across every valley, pointing in the direction of dip

It forms a closed circular outcrop centred on the highest hill

It follows (runs parallel to) the topographic contours

Downstream (the V points in the dip direction)

Upstream, against the flow of the river that crosses it

It is horizontal, since the V shows the bed lies flat

It is vertical, since a downstream V means no measurable dip

To make the finished cross-section appear longer and more impressive on the page

To avoid exaggerating and distorting the dips and structures

It does not matter what scales you use, as the angles stay correct either way

To hide any faults so the section looks like a simple, undeformed sequence

As a boundary where younger beds rest on and truncate the eroded older ones

As a set of beds that simply follow the topographic contours without any break

As a line that offsets (displaces) the outcrops of the beds it cuts

As a circular outcrop that closes on itself around a central point

The shallower dip measured in any oblique direction across the bedding plane surface

The horizontal line drawn across the bed at right angles to the direction of steepest slope

Always exactly zero, because true dip is by definition measured along the strike line itself

The angle of maximum slope of the bed below horizontal, measured perpendicular to strike

The true dip is the maximum slope, so any oblique direction climbs less steeply

Apparent dip is simply measured more accurately with a clinometer than true dip is

Apparent dip is always larger because oblique sections cut the bedding at steeper angles

They are always exactly equal, since both are measured down the same bedding plane

50 m

25 m

43 m

100 m

Cosine: t = w cos(theta)

Tangent: t = w tan(theta)

Sine: t = w sin(theta)

None; thickness equals width

Hand samples are always weaker than the rock mass, so the mass is invariably the stronger of the two

The rock mass has no weight of its own, so it cannot resist any applied load at all

Rock mass strength depends only on the colour and grain size of the intact mineral crystals

Discontinuities (joints, bedding, faults) break up the mass and can act as planes of weakness

To determine the ground conditions so hazards are identified and safe foundations designed

To choose the colour and external cladding of the building before construction begins on site

To measure the annual rainfall across the site so the drainage gutters can be sized correctly

To date the fossils in the bedrock so the geological age of the site can be recorded officially

Drilling many boreholes across the whole site immediately, before any records are consulted

A desk study of maps, old records and aerial photographs

Pouring the concrete foundations first and checking the ground conditions afterwards

Demolishing every existing structure on the site before any ground data is gathered

It is far too strong and rigid to excavate, so foundations cannot be dug into it at all

It drains so freely that any water passes straight through without affecting the ground

It expands and contracts with water content, heaving and subsiding to crack structures

It never changes its volume, so it provides a perfectly stable and unchanging base

Strong, unweathered granite bedrock at shallow depth

Thick, free-draining river gravel above the water table

Solid, well-cemented sandstone with no open joints

Solution cavities in soluble limestone

Deep (piled) foundations carrying the load through the clay to the sandstone

Shallow strip foundations resting directly within the soft compressible clay layer

No foundations at all, placing the structure straight onto the levelled ground surface

Building only on the bare surface of the clay and spreading the load with a thin slab