Study the map of Taita Hills 1:50,000 (sheet 189/4) and answer the following questions.

(a)
The four-figure grid reference of Rigga Hill is $\boxed{3870}$.

(b)
Step 1: Measure the length of road AB on the map.
Length on map = 28 cm.

Step 2: Determine the representative fraction (RF) of the map.
RF = $1 : 50000$.

Step 3: Convert map length to ground distance in km.
$1\ cm (map) = \frac{50000}{100000}\ km (ground) = 0.5\ km.$
Ground length = map length $\times 0.5\ \text{km/cm}$.

Step 4: Substitute the measured length.
$28\ cm \times 0.5\ \frac{km}{cm} = 14\ km.$

The length of road AB is $\boxed{14\ km}$.

(c)
The area experiences a modified equatorial climate.
Evidence:

• High altitude (over $1500$m e.g. Rigga Hill). Cool temperatures.
• Forest vegetation on hilltops. High rainfall.
• Perennial rivers e.g. Voi River. Reliable rainfall.
• Dense nucleated settlements on hilltops. Fertile volcanic soils and adequate rainfall.
• Tea and coffee growing areas. Cool moist conditions.

(d)(i) Causes of migration from the area (citing map evidence):

1. Steep slopes/relief (mountainous terrain around grid square 3870). Difficult for farming/mechanisation. People migrate to lowlands.
2. Congestion/overpopulation (dense settlements e.g. Wundanyi, dense housing). Limited land pushes people out.
3. Poor transport (few roads, winding e.g. A to B road). Limits market access, encourages out-migration.
4. Limited economic opportunities (few industries, subsistence farming shown). Youth migrate to urban centres like Mombasa.

(d)(ii) Factors influencing agricultural activities (citing map evidence):

1. Relief: Steep slopes (Taita hills) limit large-scale farming; terracing used.
2. Climate: High rainfall (forests, perennial rivers) favours crops like tea/banana.
3. Soils: Fertile volcanic (hilltop farms, dense population). Supports cash crops.
4. Drainage: Poor in valleys (swamps) limits cultivation there.

(e)
Two rocks of volcanic origin:

1. Basalt
2. Pumice
   Basalt, Pumice

(f)(i) Mechanical formation of soil:
Physical weathering breaks down pre-existing rocks into smaller particles without chemical change.

• Temperature changes cause exfoliation (expansion/contraction).
• Frost action: Water freezes in cracks, expands, splits rocks (in highlands).
• Action of wind-blown sand grinds rocks (abrasion).
  Results in angular fragments forming soil.

(g)(i) Three problems during data collection on rocks in local environment:

1. Difficult terrain (steep slopes, thick vegetation). Hard to access sites.
2. Weather (heavy rains). Makes fieldwork hazardous/slippery.
3. Limited tools (no advanced equipment for sampling). Rely on observation.

(g)(ii) Two economic uses of rocks likely to identify:

1. Building stones (quarries shown on map).
2. Ballast for roads (crushed rock along roads).

(h)(i) Two types of weathering:

1. Physical/mechanical weathering.
2. Chemical weathering.

(h)(ii) Two ways through which the strength of an earthquake is measured:

1. Richter scale: Measures magnitude/amplitude of seismic waves using logarithm. E.g. 5.0 is 10x stronger than 4.0. Records energy released at source.
2. Modified Mercalli Intensity (MMI) scale: Measures effects/intensity on surface (I-XII). E.g. VIII causes damage to buildings. Subjective based on observations.