GRADE 9 Social Studies NATURAL AND HISTORIC BUILT ENVIRONMENTS – INTERNAL LAND FORMING PROCESSES Notes
NATURAL AND HISTORIC BUILT ENVIRONMENTS
Subtopic: INTERNAL LAND FORMING PROCESSES
These notes explain how forces inside the Earth (internal or endogenic processes) shape the land. The language and examples are aimed at learners in Kenya, age 14. You will find definitions, easy diagrams, Kenyan examples and short activities to help you learn.
1. What are internal land forming processes?
Internal processes are movements and changes that start deep inside the Earth. They include folding, faulting, volcanic activity, earthquakes and uplift. These processes can make mountains, valleys, rift escarpments, volcanoes and hot springs.
2. Main internal processes (simple explanation, cause and Kenyan examples)
- What: Rocks bend into waves called folds (anticlines and synclines).
- Cause: Horizontal pressure inside the crust (compression).
- Effect: Often forms ridges and folded mountains over long time.
Kenyan example: Parts of western Kenya show folded rocks in older highlands; folding often works together with other processes to form highlands.
- What: Breaks in the Earth's crust where blocks of rock move past each other.
- Cause: Tension, compression or sideways forces. Faults can be normal, reverse or strike-slip.
- Effect: Creates rift valleys, escarpments and displacement of land.
Kenyan example: The Great Rift Valley was formed by huge normal faults. You can see escarpments (cliffs) like the Elgeyo and Mau escarpments along the Rift.
- What: Magma rises and erupts as lava, ash and gases forming volcanic mountains, cones and craters.
- Cause: Melted rock (magma) under pressure finds a way to the surface.
- Effect: Builds mountains, produces fertile soils; can also destroy property during eruptions.
Kenyan examples: Mount Kenya (old volcanic dome), Mount Elgon (massive extinct volcano), Mount Longonot (crater near Naivasha), Menengai caldera and the volcanic fields around Lake Turkana.
- What: Sudden shaking of the ground caused by rapid movement along faults or volcanic activity.
- Cause: Built-up stress is suddenly released along fault lines or during volcanic eruptions.
- Effect: Damage to buildings, landslides, ground cracks and sometimes loss of life.
Kenyan note: Earthquakes occur mainly along the Rift valley system. Communities living near the Rift should be aware and prepared.
3. How internal processes have shaped Kenya
- Great Rift Valley: Formed by long-term faulting — has escarpments, rift lakes (Nakuru, Naivasha, Turkana), and flat valley floors.
- Volcanic highlands: Mt Kenya and Mt Elgon formed by ancient volcanic activity — these areas have fertile soils used for farming.
- Geothermal energy: Rift areas like Olkaria provide steam for geothermal power (important for Kenya’s electricity).
- Tourism and landscape: Craters, hot springs and mountains attract visitors (e.g., Mount Longonot, Menengai, Hell’s Gate).
4. Positive and negative effects on people
Positive: Fertile soils for farming, geothermal energy, minerals, tourism.
Negative: Earthquakes and volcanic eruptions can destroy homes and lives; faulting and landslides can damage roads and farms.
5. Classroom activities and field study ideas
- Locate the Great Rift Valley, Mount Kenya, Mount Longonot and Menengai on a map of Kenya.
- Draw a simple cross-section to show a normal fault and label the hanging wall and footwall.
- Visit a safe nearby site (e.g., Hell’s Gate visitor centre) or invite a geologist to speak about Rift Valley geology.
- Make a short poster describing how geothermal energy from Rift faults helps Kenya produce electricity.
6. Key terms (short meanings)
- Endogenic processes: Forces and movements inside the Earth.
- Fold: Bend in rock layers (anticline = up, syncline = down).
- Fault: Break in rock where movement occurs.
- Rift valley: A long lowland between faults caused by crust pulling apart.
- Volcano: Opening in Earth where magma reaches the surface.
- Epicentre: Point on the surface above an earthquake focus.
- Geothermal: Heat energy from inside the Earth (used for power).
7. Quick revision questions
- What is the difference between folding and faulting?
- Name two volcanoes or volcanic features in Kenya.
- How did the Great Rift Valley form?
- Mention one benefit and one danger of living near a volcano or Rift area.
- What is the epicentre of an earthquake?
Answers (check your work)
- Folding bends rock layers without breaking them; faulting breaks the rock and moves blocks past each other.
- Examples: Mount Kenya, Mount Elgon, Mount Longonot, Menengai caldera.
- The Rift formed as the crust stretched and broke along many normal faults (crust pulled apart).
- Benefit: Fertile soil or geothermal energy; Danger: eruptions or earthquakes can destroy property and cause loss of life.
- The epicentre is the point on the ground directly above where the earthquake starts (the focus).
Study tip: Use maps and simple cross-sections when revising. Drawing helps you remember how folding, faulting and volcanism work.
Prepared for Social Studies learners (age 14) — Kenyan context. Keep safe when observing landforms: follow teacher or guide instructions on field trips.