Need for Slides by Dr C. Kifunda

1. GO 111
Background to
Geomorphology
Dr. C. Kifunda
Office No 4B

3. Topic 1: Origin and
Structure of the Earth
1.1 The origin and age of the Earth
1.2 The internal structure of the earth
1.3 The continental drift theory and isostacy
1.4 Plate tectonics theory (crustal rearrangement)

4. Introduction
General introduction of Geography
The concept of Geomorphology
i. Geomorphology definition
ii. Geomorphologist definition

5. Introduction cont …
Definition of geography: Eratosthenes, an Ancient
Greek Scholar first coined the term "Geography”.
Geography has two words which are “geo” and
“graphein”. Geo mean the earth and graphein
means description of..
Therefore, geography is the description of the earth
as the habitat of humankind.

6. Introduction cont …
Haggett, 1983, defined Geography as the study of the
location and distribution of living things and the earth
features among which they live.
Generally Geography can be defined as the Science of
the Earth's surface, which describes and analyses the
spatial variations in physical, biological, and human
phenomena that occur on the surface of the earth and
treats their interrelationships.

7. Introduction cont …
Types of Geography and their components
Geography has been called "the world discipline" and
"the bridge between human and physical science".
Geography is divided into two main branches: human
geography and physical geography.

8. Introduction cont …
Table 1: Showing components of physical and human geography

9. Introduction cont …
Major sub disciplines of physical and human geography

10. Introduction cont …
The Figure above indicates that the study of geography
can also involve a holistic synthesis which connects
knowledge from a variety of academic fields in both
human and physical geography.
Apart from the branches of geography here are also
major geographical techniques which are Cartograph,
Geographical Information System (GIS) and Remote
Sensing.

11. Introduction cont …
Cartography: this involves the techniques concerned with
constructing maps from geographic information.
Remote sensing: is the acquisition of information about an
object or phenomenon without making physical contact with
the object.
A geographic information system (GIS) is a system
designed to capture, store, manipulate, analyze, manage,
and present all types of geographical data. The key word to
this technology is Geography.

12. Importance of studying geography
To understand basic physical systems that
affect everyday life (e.g., earth-sun
relationships, water cycles, wind and ocean
currents).
To learn the location of places and the
physical and cultural characteristics of those
places in order to function more effectively in
our increasingly interdependent world.

13. Importance of studying geography
To understand the geography of past times and
how geography has played important roles in the
evolution of people, their ideas, places and
environments.
To develop a mental map of your community,
province or territory, country and the world so that
you can understand the “where” of places and
events.

14. Importance of studying geography
To explain how the processes of human and
physical systems have arranged and sometimes
changed the surface of the Earth.
To recognize spatial distributions at all scales
i.e. local and worldwide; in order to understand
the complex connectivity of people and places.
To understand global interdependence and to
become a better global citizen

15. Importance of studying geography
To be able to make sensible judgements about
matters involving relationships between the
physical environment and society.
To appreciate Earth as the homeland of
humankind and provide insight for wise
management decisions about how the planet’s
resources should be used.

16. The concept of Geomorphology
The word “geomorphology" comes from the
Greek roots "geo,“ “morph,” and “logos,”
meaning “earth,” “form,” and “study,”
respectively. Therefore, geomorphology is
literally “the study of earth forms.”
The general meaning of geomorphology is the
study of landforms and the processes that create
them.

17. The concept of Geomorphology
Geomorphologists are concerned primarily with earth’s
surficial features, including their origin, history,
composition, and impact on human activity.
Geomorphology concentrates primarily on Quaternary
(Pleistocene and Holocene) features.
 Earth’s landforms reflect the local and regional balance
between hydrologic, tectonic, aeolian, glacial,
atmospheric, and marine processes.

18. 1.1 The origin and age of the Earth
Approaches about the origin of the earth
Evolution Approach
Some scientists like Charles Darwin, Charles Lyell,
Lord Kelvin, Herman Von Helmholtz and Comte de
Buffon advocates on evolution of he earth.
They uses fossils and geologic records to construct
a very long history of the earth and its life.

19. The origin and age of the Earth cont …
The proponents of evolution believe that the Earth
Seen from space has changed dramatically.
They argue that one hundred million years after it
had formed (some 4.35) billion years ago, the planet
was probably undergoing meteor bombardment.
Read the theory of accretion postulated by Otto
Schmidt (1994) for more information.

20. The origin and age of the Earth
cont …
Creation Approach
The advocates for creation approach
believed that the Earth was created by God.
Archbishop Ussher in 1654 declared that
the Earth has 5,658 years old.

21. The origin and age of the Earth
cont …
He added up all the generations after Adam
and came up with an age of the Earth as
5,658 years old, having formed in 4004 B.C.
Today most creationists estimate earth’s age
is about 10000 years old.

22. The origin and age of the Earth
cont …
Some scientist think evolution and bible fit
together perfectly i.e., God supernaturally
initiated the evolutionary process by:
 Creating the universe
Planting DNA on earth
All these theories are based on
assumptions that can never be proven

23. 1.2 The internal structure of
the Earth
The internal structure of the earths consists
layers.
Earth’s layers can be classified either by their
composition or by their mechanical behavior
(strength).
 By composition (

24. Compositional classification
By compositional classification the Earth’s
Internal Structure consist of
1.Crust or skin
2.Mantle
3.Core

25. A. Crust or skin
This is the solid outer layer of the Earth.
 Its depth is usually never more than 1 percent
of the Earth’s radius.
It has been categorized into Oceanic and
Continental crusts.

26. The continental crust
Known as sial (rich in silica and aluminium).
Composed mainly of granitic rocks.
Average 35–40 km in thickness but can be up
to 70 km thick under mountain ranges.
Relatively less dense than oceanic crust
(average density 2.7g/cm³; NB soil = 2.75g/cm³).

27. The Continental Crust cont …
Cannot be sub ducted, but instead ‘floats’
above the denser oceanic crust.
Occurs only under large land masses or
continental shelves, or beneath certain shallow
seas, and forms 30–40 per cent of the total
crust.

28. The Continental Crust cont …
Relatively older than oceanic crust –
the world’s oldest rocks are the great
continental shields, e.g., North America,
Australia.

29. The Oceanic Crust
Known as sima (rich in silica, and magnesium).
 Composed mainly of basaltic lavas.
 Average 6–10 km in thickness.
 Relatively denser than continental crust (The
average density of oceanic crust is 3.0 g/cm³; NB
the average density of water = 1.0 g/cm³).

30. The Oceanic Crust cont …
Can be sub-ducted beneath continental crust
as it is denser. At its deepest (in subduction
zones), has a temperature of1200°C.
Occurs under the oceans and forms 60–70 per
cent of the total crust.
 Relatively younger than continental crust (is
destroyed at subduction zones and is recycled).

31. The mantle
This is the zone within the Earth’s interior
ranging from 25 to 70 km below the surface, to a
depth of ~2,900 km.
It is composed mainly of silicate rocks, rich in
iron and magnesium.
It is a layer between the crust and the outer core

32. The Mantle cont …
The boundary between the mantle and the
core is known as the Gutenberg discontinuity.
And the boundary between crust and mantle
is Mohorovicic discontinuity.
The mantle is divided into sections (layers) :-
i. The upper mantle
ii. The lower mantle

33. The core
Core is the layer beneath the mantle.
This is the very centre of the Earth and is
composed of iron and nickel.
It consists of an outer core (semi-molten) and
inner core (solid).
The temperature at the very centre of the Earth
may reach 5,500°C.

34. The Outer core
The Outer Core: Composed of molten metal, it is
1,130 miles thick; the magnetic field is caused by
electric currents circulating inside the outer core.
It is a layer of molten metal that surrounds the inner
core.
Despite the pressure from the rock above, it is
liquid.

35. The Inner Core
The Inner Core: composed of iron and nickel, it is
subject to so much pressure that it remains in a solid
state in spite of temperatures higher than 9,000°F; its
diameter is 1,000 miles.
The inner core is a dense ball of solid metal. In the
inner core, extreme pressure squeezes the atoms of
iron and nickel so much that they cannot spread out
and become liquid.

36. Figure showing the internal
structure of the earth

37. Temperature in the interior of the
Earth
About 20 meters below Earth’s surface, rock
begins to get warmer.
For every 40 meters that you descend from
that point, the temperature rises 1 degree
Celsius.

38. Temperature cont ….
This rapid rise of temperature continues for
several tens of km and continues to grow hotter
and hotter approaching the core.
The high temperatures inside Earth are a result
of heat left over from the formation of the planet.

39. Pressure
The more you descend into Earth’s interior, the
amount of pressure increases.
Pressure results from a force pressing on an area.
Because of the weight of the rock above, pressure
inside the Earth increases as you go deeper. The
deeper you go, the greater the pressure.

40. Mechanical layering classification
There are two layers
 Uppermost layer is the lithosphere (sphere of
rock), which comprises the crust and a solid portion
of the upper mantle.
 It is divided into many plates that move in relation
to each other due to tectonic forces.

41. Mechanical layering classification cont …
The second layer is an asthenosphere.
 The asthenosphere allows the solid lithosphere to
float at the top of it.
It a semiliquid layer known as (weak sphere),
which enables the lithosphere to move around.

42. Thank you for your
attention