S1 Unit 5 Geography - Rwanda

1. UNIT 5: FORMS OF
RELIEF

2. LEARNING OBJECTIVES
In this unit, the learner will be able to:
•Define relief.
•Identify the different forms of relief.
•State the relationship between relief and
human activities.

3. SLOPE, ALTITUDE AND CONTOURS
❖ Slope: is the rise or fall of the relief feature. It is a measure
of the degree of inclination of a feature in relation to the
horizontal plane.
Slope is determined by the angle of elevation.
Slopes are classified in the following types:
a) Concave slope
b) Convex slope
c) Steep slope
d) Gentle slope

4. TYPES OF SLOPES
a) Concave slope: this is a slope that has a steep section uphill and a
comparatively gentle section downhill. It is known as waning slope
b) Convex slope: this is a slope that is more or less gentle uphill but
comparatively steeper downhill
c) Gentle slope: this is a slope which is almost flat. Its elevation is flat
compared to the convex, concave, and steep slopes.
d) Steep slope: this is a slope that is almost vertical or relatively high
gradient.
Gradient: refers to steepness or gentleness of an area.
Even slope: is the term which is used when there is uniform change in
gradient between two points on the earth’s surface.

5. Steep slope

6. ALTITUDE
Altitude: this is the height or
elevation of a point above a
given reference point.
The reference point is the sea
level which is at a zero meter.
Altitude is expressed in feet
or meters.
Therefore, altitude is defined
as the height above the sea
level.

7. CONTOURS
A contour: is a line connecting points (places) of the same altitude on a
topographical map. Contours show the type of relief on the earth's
surface.
Interpretation of contours
✓Contours appearing close to each other represent Steep Slope
✓Contours spreading over a large area represent Extensive Plain
✓Contours forming concentric circles represent Hill or Mountain
✓Contours appear to overlap or cross each other represent Cliff
✓Contours are V or U shaped represent Valley.

9. FORMS OF RELIEF FEATURES
Relief features are classified into two main categories. These include
a) The continental relief features
b) The marine relief features
These relief features had been formed by both internal and external forces:
The internal forces such as:
• Tectonic plate movement,
• Vulcanicity,
• Earthquakes,
The external agents such as:
• Winds, ice,
• Rain leading to mass wasting and
• Erosion and deposition.
Vulcanicity as cause of major relief features

10. CONTINENTAL RELIEF FEATURES
The main forms of continental relief include the following:
a) Mountain: is a very large landform that rises above the area surrounding it.
It usually has a peak. Mountains may appear as single landmass or in a
chain called range.
Example mountains are:
❖ Mount Everest (8,848m) in Tibet (China-Nepal) found in Himalaya ranges. it
is the highest peak mount in the world
❖Mount Kilimanjaro (5,895m): It is found in Tanzania. It is the highest peak
mountain in Africa
❖Mount Karisimbi (4,507m): The highest peak mountain in Rwanda
❖Mount Aconcagua (6,960m): The highest peak in South America located in
Andes Mountain range in Argentina
❖Mount Denali (6,144m): The highest peak in North America located in Alaska
range in USA.

11. Mount Denali 6,144m Mount Aconcagua 6,960m
Comparison of mountains in the world
Himalaya mountain range is located in Asia and is
known to have highest mountain peaks in the world
Himalaya mountain range is located in Asia and is
known to have highest mountain peaks in the world

12. TYPES OF MOUNTAINS
Mountains are classified into the following types:
❖Block mountain: these mountains form due to the process of faulting. For
example, Mount Rwenzori (5,111m) in Uganda and DRC border
❖Volcanic mountains: these mountains forms due to the process of vulcanicity
(volcanic eruption), for example: Mt Elgon (4,321) between Kenya and
Uganda.
❖Fold mountains: these mountains form due to the process of folding. For
example;
❖Atlas range in northeast and Cape range in southeast of Africa
❖Himalayas in Asia
❖Andes mountain range in South America
❖Rockies in North America
❖Inselberg: these mountains form due to erosion, and accumulation of snow
and ice on the continent or sea/ocean.

14. b) Hill: this is a landmass that extends above the surrounding
terrain. However it is smaller than a mountain
c) Plateau: is a raised land that is almost flat at the top with
gentle slopes on all sides to the lower ground. For example,
the central plateaus of Rwanda, and the eastern African
plateaus in Africa.
d) Ridge: this is a linear, steep-sided upland. It is a relief
feature that consists of a chain of hills or mountains.
e) Escarpment: This is a steep slope that separates an area of
high ground from an area with lower ground.
f) Spurs: this is an area of high ground that sticks out of a
mountain hill

15. Hill Plateau
Ridge
Escarpments

16. g) Plain: this is an extensive area tract of flat land.
Plains are categorized into:
❖Peneplains: these form due to the wearing down of lands that were once
much higher. For example: Karamoja, Soroti in Uganda
❖Alluvial (flood) plains: these form
due to the accumulation of silts
brought down by rivers. For example;
Nyabarongo plain
❖Coastal plains: these form
alongside the coast due marine
deposition. For example, Rufiji Delta
on the coast of Tanzania
Flood Plain on Nyabarongo
river

17. h) Valley: This is a low area of land between hills or mountains, typically
with a river or stream flowing through it.
There are two types of valleys:
❖U-shaped valleys: these valleys are found between hills with gentle
slopes.
❖V-shaped valleys: these valleys are found between mountains with steep
slopes.
U Shaped Valley V Shaped Valley

18. MARINE RELIEF FEATURES
These are landforms that are found on the oceanic crust. They include beaches,
gulfs, cliffs, and capes.
Beaches
Gulf of Mexico
Cliff
Cape

19. The main relief features of the ocean bed

20. 1. Continental shelf: is an underwater
landmass extends from the shorelines
towards the ocean deep. This region
represents 7.5% of the total ocean
area.
Continental shelves are wide in Japan,
Canada, U.S.A but narrow in Africa.
2. Continental slope: this is a steep
slope that extends from the edge of
the continental shelf to the deep
ocean plain. It consists of mud, and
silt, and is often cross cut by
submarine canyons. It is widely
20kms.

21. 3. Continental rise: is an
underwater feature found
between the continental
slope and the abyssal plain.
4. Continental ridge: this is a
submarine mountain formed
from ocean volcanic
eruption. For example,
• East pacific ridges,
• Atlantic mid-ocean ridge, and
• Mid-Indian ocean ridge.

22. 5. Oceanic trench: this is long
narrow steep-sided depression in
the oceanic crust. It is the deepest
part of the ocean. For example,
• Marianna trench in Pacific
Ocean with 10,994meters below
sea level.
• Java trench in Indian ocean,
• Tonga trench in Pacific ocean,
• Peru-Chile trench in Pacific
Ocean
• Atacama trench in Pacific ocean

23. 6. Abyssal plain: is
underwater plain on the
deep ocean floor which
is usually found at
depths between 3,000
and 6,000meters.
It extends from continental
rise to mid-ocean ridge. It
therefore covers 50% of the
earth’s surface.

24. 7. Oceanic island: is that rises to the surface from the floor of ocean basins.
Oceanic islands are formed by the continuous eruption with oceans. When these
oceanic islands are eroded, it results in formation of guyots. Examples:
• Azores, Ascension and Saint Helena islands in Atlantic ocean,
• Hawaiian islands in Pacific ocean.
• Madagascar island in Indian Ocean
Mnemba Island of Zanzbar in Tanzania

25. FIGURES SHOWING MARINE RELIEF FEATURES

27. RELIEF FEATURES AND HUMAN ACTIVITIES
❖Hill tops favour the construction of telephonic communication masts
❖Gentle sloping areas favour farming, construction of roads, and
settlement
❖Flat valleys promote rice, sugarcane and vegetable growing because of
the presence of water in them
❖Plains tend to favour cattle rearing, construction of railway lines, and
aerodromes, etc…….
❖Mountainous areas promote forestry which later favours lumbering
and attraction of tourists
❖Steep slopes hinder farming, transport and communication
development.
❖Steep slopes are less exploited because it demands high capital