grade 9-geography_fetena_net_e7de

FEDERAL DEMOCRATIC REPUBLIC OF ETHIOPIA MINISTRY OF EDUCATION GEOGRAPHY STUDENT TEXTBOOK GRADE 9

Take Good Care of This Textbook

  • This textbook is the property of your school, handle with care.
  • Ten ideas to help take care of the book:
    1. Cover the book with protective materials.
    2. Keep the book in a clean dry place.
    3. Ensure hands are clean when using the book.
    4. Do not write on the cover or inside pages.
    5. Use paper or cardboard as a bookmark.
    6. Never tear or cut out pictures or pages.
    7. Repair any torn pages with paste or tape.
    8. Pack the book carefully in your school bag.
    9. Handle the book with care when passing it to another person.
    10. When using for the first time, lay it on its back and open a few pages at a time, pressing lightly along the bound edge.

Credits

  • Writers: Muluemebet Worku (Ph.D), Kidanemariam Paulos (Ph.D.)
  • Editors: Sintayehu Teka (M.Sc.) (Content Editor), Kassie Molla (M.A.) (Language Editor), Hirut Woldemichael (M.A.) (Curriculum Editor)
  • Illustrator: Agenchw Nega (M.Sc.)
  • Designer: Geda Hoka (M.A.)
  • Evaluators: Tesfaye Shiferaw (PhD), Abebe Yibeltie (MA), Hussein Seid (MA)
  • Published by: FDRE, MINISTRY OF EDUCATION
  • In collaboration with: HAWASSA UNIVERSITY

Copyright Information

  • First Published by the Federal Democratic Republic of Ethiopia, Ministry of Education.
  • Supported by various international organizations and programs.
  • ©202 by the Federal Democratic Republic of Ethiopia, Ministry of Education. All rights reserved.
  • No part of this textbook may be reproduced without prior written permission.
  • Copyrighted materials used by permission of their owners.
  • Printed by: GRAVITY GROUP IND LLC, Sharjah UNITED ARAB EMIRATES
  • ISBN: 978-99990-0-048-2
  • August 3, 2023

UNIT ONE: GEOLOGICAL HISTORY AND TOPOGRAPHY OF ETHIOPIA

Introduction

  • Grade 8 review: physical characteristics of the Earth, socioeconomic activities, natural resources, modern history of Ethiopia, and contemporary global issues.
  • Grade 9 focus: the geography of Ethiopia (physical, human, and economic environments).
  • Topics include the country’s location, size, shape, geological history, topography, drainage, climate, vegetation, wildlife, soil, mineral resources, major economic activities, and human-natural environment interactions.
  • Also includes geographic enquiry skills and techniques.
  • Introduces basic concepts related to geography (meaning, scope, and branches).

Unit Outcomes

  • Recognize the concept, scope, and branches of geography.
  • Express the basic land features of the physical environment.
  • Describe the absolute and relative location of Ethiopia.
  • Analyze the effects of shape and size of Ethiopia on its sociocultural, political, and economic condition.
  • Explain geologic processes that shaped the land surface of Ethiopia.
  • Describe the different landforms of Ethiopia.

1.1 Geography: Meaning, Scope and Branch

Objectives

  • Define geography as a subject.
  • Describe the scope of geography.
  • Identify the branches of geography.

1.1.1 Meaning of Geography

  • The term “Geography” originated in Greek civilization.
    • Geo – means earth
    • Graphos – means writing
  • Eratosthenes (276-194 B.C.) coined the term Geography and defined it as “the field of study that deals with the description of the earth”.
  • Definitions of Geography by various scholars:
    • Eratosthenes (276-196 BC) – Geography is the description of the earth.
    • Alexander Von Humboldt (1769-1859) - Geography is a synthesizing discipline to connect the general with the particular through measurement, mapping, and a regional emphasis.
    • Concise Oxford Dictionary (1964) - Geography is the science of the earth’s surfaces.
    • Hartshorne, R. (1899-1992) – Geography is a branch of knowledge that is concerned with the provision of an accurate, orderly and rational description of distributions on the surface of the earth.
    • Yeates, M. (1968) – Geography is a science that is concerned with the rational development and testing of theories that explain and predict the spatial distribution and locations of things and phenomena on the surface of the earth.
  • Geography studies the earth, primarily its surface.
  • Geography is the scientific study of the Earth that describes and analyses spatial and temporal variations of physical, biological and human phenomena, and their interrelationships and dynamism over the surface of the Earth.

1.1.2 The Scope of Geography

  • Scope refers to the content of the field of study.
  • The scope of geography is dynamic and changes with discoveries and ideas.
  • Geography studies physical and human features, including causes, effects, and interactions.
  • Subjects include features in the hydrosphere, atmosphere, lithosphere, biosphere, and anthroposphere.
    • Hydrosphere – all bodies of water.
    • Biosphere – all living organisms.
    • Atmosphere – air composition.
    • Lithosphere – solid layer of rocks.
    • Anthroposphere – part of the environment made or modified by humans.
  • Geography is concerned with economic, social, political, and ecological problems.
  • Utilizes modern technology like GPS and GIS for analysis.
  • Major areas of focus:
    • The earth, its position in the universe and its movements
    • Physical features, forces, and changes over time
    • Relationships between human beings and the natural environment
    • Atmospheric conditions, weather, and climate
    • Materials that make up the earth and its diverse landforms
    • Major economic activities of humans and their impacts on the environment.
  • Geography is a holistic discipline of knowledge and research.

1.1.3 Branches of Geography

  • Two main branches:
    • Physical geography
    • Human geography
A. Physical Geography
  • Studies the distribution of natural features such as climate, landforms, soil, vegetation, surface drainage systems, water resources, and animals.
  • Sub-branches:
    • Geomorphology
    • Climatology
    • Oceanography
    • Biogeography
    • Soil geography
    • Phytogeography
    • Zoogeography
B. Human Geography
  • Studies the distribution and influence of human aspects, including cultures, population settlement, economic activities, and political systems.
  • Sub-branches:
    • Economic Geography
    • Population Geography
    • Urban Geography
    • Political Geography
    • Historical Geography
    • Cultural Geography

1.2 Location, Size and Shape of Ethiopia

Objectives

  • Describe the absolute and relative location of Ethiopia.
  • Discuss the effects of the size and shape of Ethiopia on its sociocultural, political and economic condition.

1.2.1 Location of Ethiopia

  • Location is a place where a particular point or object exists.
  • Expressed in two ways:
    • Relative location
    • Absolute location
A. Relative Location of Ethiopia

  • Position of a place in relation to other geographic features.

  • Two types:

    • Vicinal location
    • Strategic location

  • i. Vicinal Location of Ethiopia

    • Ethiopia is a landlocked country surrounded by six neighboring countries.
    • Total boundary line: 5,260 km.
    • Boundaries with:
      • Djibouti (310 km) - West of Djibouti
      • Eritrea (840 km) - South of Eritrea
      • Kenya (760 km) - North of Kenya
      • Somalia (1,600 km) - West and Northwest of Somalia
      • Sudan (744 km) - East and Southeast of Sudan
      • South Sudan (1,006 km) - Northeast of South Sudan
    • Longest border with Somalia; shortest with Djibouti.

  • ii. Strategic Location of Ethiopia

    • Also called natural or global location.
    • Located:
      • in northeastern (Horn) Africa
      • to the southwest of the Asian continent
      • in the Nile Basin
      • to the south of Europe
      • to the northwest of the Indian Ocean
      • to the southwest of the Red Sea
      • to the south of the Mediterranean Sea.
B. Absolute or Astronomical Location of Ethiopia
  • Expressed as a geographical extent, in terms of latitudes and longitudes.
  • Located between 3°N – 15°N latitudes and 33°E – 48°E longitudes.
  • Extreme points:
    • Northern tip of Tigray in the north
    • Moyalle in the south (Borena).
    • Akobo in the west (Gambella)
    • the tip of Ogaden in the east (Ogaden)

1.2.2 Size of Ethiopia

  • Tenth largest country in Africa.

  • Total area of 1,106,000 square kilometers.

  • Contains about 0.7 percent of the world’s land area and about 3.6 percent of Africa’s land mass.
    *Comparison of Ethiopia’s Areal Size with its Neighbors

    CountryTotal area (in sq.kms)RankSize in comparison to EthiopiaSource
    Ethiopia1,106,0002−CSA, 2012
    Sudan1,849,23311.01 times biggerCSA, 2012
    Somalia637,66131.73 times smallerCSA, 2012
    Kenya580,00051.91 times smallerCSA, 2012
    Eritrea118,00069.42 times smallerCSA, 2012
    Djibouti23,2007Almost 50 times smallerCSA, 2012
    South Sudan631,92841.75 times smallerCSA, 2012

  • Ethiopia is the largest country in the Horn. Advantages of large size:

    • diverse agro-ecological zones
    • large amount of arable land
    • great variety of mineral resources
    • home to diverse ethnic groups.

  • Disadvantages of large size:

    • expensive administrative expenditure
    • large army to protect its sovereignty
    • great financial power to construct infrastructural facilities
    • challenges for effective administration and socio-economic integration.

1.2.3 Shape of Ethiopia

  • Varies among countries.
  • Shapes affect administrative, defense, and economic integration.
  • Ethiopia has a more or less compact (circular) shape because the extreme north-south and east-west spans of the country cover comparable distances.
  • Indicators of compactness:
    • the boundary - circumference ratio (B/C);
    • the area - boundary ratio (A/B);
    • the actual area - area of the inscribing circle (A/A’).
  • Formula to find the circumference of a circle having equal areal size as the country under consideration is 2πr (π=3.14 ).
  • Area of the circle is calculated taking the following formula (i.e. A=πr^2).
  • Example B/C ratio of Ethiopia:
    B/C =
    \frac{5260}{3727.18} = 1.411
    This value implies that the shape of Ethiopia has a deviation of 41% from the assumed theoretical circular shape it ought to have.
  • Estimation via A/B ratio: The index of compactness using A/B ratio for Ethiopia is indicated hereunder.
    • It implies that if 1 km borderline is safeguarded by national army, 210 km2 of the hinterland will become free from the assault of an enemy.
  • The ratio of actual area to the area of the smallest inscribing circle (A/A’) = actual area/area of the smallest inscribing circle . Lower value near 0 indicates elongation and a higher value near 1 suggests more compactness.

1.3 Geological History of Ethiopia

Objectives

  • Explain the geological history of Ethiopia.
  • Distinguish the geological processes that result in the current landform of Ethiopia.
  • Describe major landforms of Ethiopia.

1.3.1 The Geological Processes in Ethiopia

  • Scientists use the geological time scale to describe geology and history of life on Earth, measuring time in eras, periods, epochs, and years.
  • Each geological era is distinguished by:
    • the relative positions of the continents
    • the character of the prevailing climate
    • the predominant lifeform (plants and animals)
  • Geological eras, in chronological order:
    • Precambrian Era
    • Paleozoic Era
    • Mesozoic Era
    • Cenozoic era
I. The Precambrian Era (from 4.5 Billion to 600 Million years ago).
  • Oldest and longest geological era.
  • Geological events in the Horn:
    • Frequent orogenic movements
    • Intensive volcanic activities
    • Denudation during the later periods
    • Formation of folded mountain
  • First forms of life emerged (one-celled, like amoeba and jellyfish).
  • The oldest rock formed – the old crystalline basement/ basement complex rock, underlies all other rocks.
  • Outcrops are found:
    • In central and northern Tigray
    • In Mettekel, Assossa, Illubabor and the Abbay Gorge
    • In central Sidama, southern Omo, southern Bale and Borena.
    • In central, western and northern Eritrea.
II. The Paleozoic Era (from 600 million years to 250 million years ago)
  • Major geologic process: denudation followed by peneplanation. No significant structural formation.
  • The only era that left a gap in rock formation in Ethiopia.
  • Denudation resulted in inselbergs (residual features).
  • Known for the predominance of invertebrates.
III. The Mesozoic Era (from 250 million years to 70 million years ago).
  • Alternate slow sinking and uplifting of the landmass (Epeirogenesis).
  • Era of sedimentary rock formation.
  • Three distinct periods:
Triassic Period
  • Landmass sank, followed by transgression of a nearby sea.
  • Adigrat sandstone formed (oldest sedimentary rock).
Jurassic Period
  • Transgression continued northwest, depositing Hintalo limestone.
Cretaceous Period
  • Landmass began to rise, and the sea started to regress southeast, depositing Upper Sandstone. Upper Sandstone is the youngest sedimentary rock and therefore overlies the rest.
  • Transgression extended up to northwestern Ethiopia.
  • Mesozoic sedimentary rocks were later buried by Cenozoic igneous rocks but exposed in:
    • southeastern lowlands of Ethiopia
    • central Tigray
    • Abbay and Wabishebelle gorges.
  • The Mesozoic is also known for the predominance of reptiles.
  • Disappearance of dinosaurs, emergence of mammals, birds, and flowering plants.
IV. The Cenozoic Era (from 70 million years to the recent time)
  • Significant structural, climatic, and biological events occurred.
  • Geologic events resulted in recent landforms.
  • Divided into Tertiary and Quaternary periods.
a. Geologic Events of the Tertiary Period (70 million - 2 million years ago)
  • Uplifting continued, forming huge blocks of dome.
  • Cracks opened, resulting in extensive basaltic lava, forming the Northwestern Highlands, the Southeastern Highlands, and the Somali plateaus.
    *Great East African Rift Valley System formed
b. Geologic Events of the Quaternary Period (2 million - recent years)
  • Recent volcanic activities after the formation of the Rift Valley.
  • Structures formed:
    • the Afar Horst that extends into Djibouti,
    • the active volcano of Ertalle in Afar,
    • the dormant volcanic mountain of Fentalle in Eastern Oromia,
    • the extensive lava field and sheets of Metahara,
    • thermal springs and fumeroles of the rift valley,
    • Pluvial rainfall in Africa and the resultant deposition.
  • The Cenozoic Era Quaternary Period is assumed to be the period in which modern man evolved.

1.3.2 Landforms of Ethiopia

  • Landform refers to individual earth surface features.
  • Great diversity of highlands, plateaus, ambas, rugged mountains, deep river gorges and lowlands.
  • Altitude varies from about 116 meters below mean sea level at the Dallol depression (Kobar sink) to 4620 m above mean sea level (a.m.s.l.) at Ras Dashen in the Semein mountain system.
  • 56 percent of Ethiopia’s land is highland.
  • Elevated surface is bisected diagonally by the Rift Valley which extends from Syria to Mozambique across the East African lakes.
  • Landforms result from two opposite forces:
    • Endogenic force (volcanic activity and tectonic forces)
    • Exogenic force that originates at the surface (denudation and penepalantion)
  • Three main physiographic divisions:
    • The Western Highlands and Associated Lowlands
    • The Southeastern Highlands and Associated Lowlands
    • The Rift Valley
I. The Western Highlands and Associated Lowlands
A. The Western Highlands
  • Stretches from Tigray in the north to the highlands of Gamo and Goffa in southwest. They are separated from the southeastern highlands by the Rift Valley.
  • Biggest physiographic region making up 44% of the area of the country.
  • Source of rivers and streams like Abbay, Baro and Tekezze.
  • Sub-divided into four groups of highlands:
    • The Plateau of Tigray
    • The North Central Massif
    • The Plateau of Shewa
    • The Southwestern Highlands
a) The Plateau of Tigray
  • Most northerly group of plateau bounded by the Mereb River in the north and the Tekezze river in the south.
  • Drained by Mereb and the tributaries of the Tekezze.
  • Composed of sandstones and limestones resulting in poor and thin soils.
  • Severe erosion due to long periods of human inhabitation.
  • Tall mountains with elevations of over 3000 meters above sea level.
    • Mount Tsibet (3988 m a.m.s.l.)
    • Mount Ambalage (3291 m a.m.s.l.)
    • Mount Assimba (3248 m a.m.s.l.)
b) The North Central Massif
  • Found between the Abbay Gorge in the south and the Tekezze Gorge in the North.
  • Contains the highlands of Gondar, Gojjam and Wollo.
  • Rivers Abbay and Tekezze along with their tributaries have formed gorges and steep sided river valleys.
  • Most rugged and dissected plateaus of Ethiopia capped by basalts of the tertiary period and surrounded by deep gorges containing small arable lands known as ambas.
  • Mountain systems in Gondar and Gojjam are separated from the eastern group of mountains in Wollo by impenetrable and deep gorges but are connected by Yeju-Wadla Delanta land bridge (ridge).
  • Gojjam Massif is the most extended tableland and is comparatively less dissected. Formed on the core of the Amedamit-Choke mountains. Carved by the Abbay river that effectively separated it from the Shewa plateau in the south and the Amhara Saynt Massif in the northeast.
  • Known for the production of cereals, such as teff, pulses and oil seeds.
    • Mount Ras Dashen – 4620 m a.m.s.l.
    • Mount Legeda – 4532 m a.m.s.l.
    • Mount Analu – 4480 m a.m.s.l.
    • Mount Tefaw Lezer – 4456 m a.m.s.l.
    • Mount Kolo – 4300 m a.m.s.l.
    • Mount Guna – 4231 m a.m.s.l.
    • Mount Abuna Yoseph – 4190 m a.m.s.l.
    • Mount Hey – 4154 m a.m.s.l.
c) The Plateau of Shewa (Central Plateau)
  • Smallest sub-division of the western highlands
  • A dome shaped plateau that serves as a watershed between the Awash, Omo- Gibe and Abbay River basins. Extends westwards into western Wollega through Horo Guduru and forms a crescent shape which causes the Abbay to swerve and drain northwards.
  • Separated by Abbay gorge in the north, the Awash River and the Rift Valley in the east, and the Gibe River in the south.
  • Drained by tributaries of the Abbay River in the west and the Awash River in the east.
    • Mount Abbuye Meda – 4000 m a.m.s.l.
    • Mount Guraghe – 3721 m a.m.s.l.
d) The Southwestern Highlands
  • South of the Abbay trough, greatly eroded due to torrential rain that pours down in the area for almost all of the year. The wettest region of the country, averaging above 1500 mm rainfall annually.
  • Includes Wollega, Illubabor, Jimma, Kafa and Gamo and Goffa.
  • Drained northwards by the Dabus and Didesa tributaries of the Abbay River, westwards by the Baro-Akobo River, southwards by the Omo-Gibe River, and eastwards by the Gojeb- Gibe River.
  • General elevation is low compared to the Northern and Eastern Highlands, with few areas above 2500 meters
  • The highest points in the region are the: Gamo-Konso Highlands, Maji-Korma Highlands, Dawuro-Konta Highlands, Tullu Wallel, and Benishangul mountain
  • Mount Gughe highest at 4200 m a.m.s.l. in the Gamo plateau.
  • Known for coffee, inset, spice production, timbering, rubber tree production, cattle, honey, and maize as well as a high percentage of forest cover.
B. The Western Lowlands
  • Extend from western Tigray in the north up to the southern Gamo and Goffa in the south, bordering Sudan and South Sudan, general elevation of 500-1000 m a.m.s.l.
  • Characterized by arid and semi-arid climate, but Baro-Akobo lowland is the wettest lowland with rivers having a regular flow of water for much of the year
  • Sub-divided into: the Tekezze and Angereb Lowlands, the Abbay-Dinder Lowlands, the Baro-Akobo Lowlands, and the Omo-Gibe Lowlands.
    • The Tekezze and Angereb Lowlands are the most northerly lowlands, drained by Tekezze and Angereb.
    • The Abbay Dinder Lowlands extend from south of Metema town up to the southern part of the Abbay River.
      Communities practice pastoralist and semi-pastoralist ways of life, but have notable towns like Humera and Metema as business centers along the Ethio-Sudanese border
II. The Southeastern Highlands and Associated Lowlands
  • Found to the southeast of the rift valley.
A. The Southeastern Highlands
  • Include the Hararghe Plateaus, the Arsi Plateau, the Bale Massif, and the Sidama Highlands
  • Their formation is similar to that of the North and Southwestern Highlands and they are capped by basaltic rock, are the main sources of the Wabe Shebelle and Genale rivers, and bounded by the fault line of the Rift Valley, the Ogaden Lowlands, and the Elkerie and Borena Lowlands.
a. The Hararghe Plateaus
  • Rises sharply from the fault line of the Rift Valley and extends gently east to Jigjiga, then falls to the Ogaden Lowlands. Drained by the left-bank tributaries of the Wabe Shebelle River. Basaltic rocks have been worn away, exposing limestones and earlier sedimentary rocks
  • Area and foothills are significant producers of coffee, chat, sorghum and millet.
    • Mount Gara Muletta (3381 m a.m.s.l.)
    • Mount Jebel Tita (3122 m a.m.s.l.).
b. The Arsi Plateau
  • Consists of the Gugu and Chillalo Massif, an extendingly rolling, suitable plateau for farming, known for wheat production. Features comparatively low because of erosion on the Arsi plateau
    • Mount Chillallo (4136 m a.m.s.l.)
    • Mount Bada (4139 m a.m.s.l.)
    • Mount Kaka (4180 m a.m.s.l.).
c. The Bale Massif
  • Next to the Arsi Plateau, separated by the headstreams of the Wabe Shebelle, known as the Wabe River; consists of a flat basaltic plateau in the north, and huge mountains in the south, also known for its barely
    • Mount Tulu Dimtu (4377 m a.m.s.l.)
    • Mount Batu (4307 m a.m.s.l.).
d. The Sidama Highlands
  • Separated from the Bale Highlands by the Genale river valley, forming the southwest extension of the southeastern highlands; plateau slopes gently south and southeast, drained by the Genale river and its tributaries
B. The Southeastern Lowlands
  • Extend from the foot hills of the southeastern highlands along the Ethio-Somalian and Ethio-Kenyan borders, between 500 and 1000 m a.s.l., including the Ogaden plains, the Elkeri plains, the Borena plains, and the Genale plains.
  • Highly extensive lowlands characterized by extreme climatic conditions with low annual rainfall (often below 500 mm), covered by sandstones and recent marine deposits
  • People practice a pastoralist way of life because of the harsh climate
III. The Rift Valley
  • The Ethiopian Rift Valley System is a narrow strip of land, stretching from the Afar Depression in the north, through the Rift Valley Lakes’ region up to Lake Turkana and Chew Bhair. Part of the Great East African Rift Valley.A set of fractures that extend from the Jordan River valley in the north, through the Red Sea, and then across East and Central Africa to Mozambique in the south.
  • Formed at the end of the Tertiary Period from tectonic epeirogenic activity, with active volcanoes, faulting, hot springs, cinder cones fumaroles, and geysers indicating geological instability. Runs diagonally and covers a total length of 1700 kilometers in Ethiopia and Eritrea
  • Ethiopian Rift Valley System comprises 18 percent of the country’s total area, and subdivided into:
    • The Afar Triangle (northern).
    • The Main Ethiopian Rift or the Lakes’ Region (central).
    • The Chew-Bahir Rift (southern).
a) The Afar Triangle (Northern Part)
  • Largest and widest part of the system, extending 200-300 kilometers. Altitude is generally low, ranging from 116 meters below mean sea level to about 900 meters above sea level.
    • Faulted depressions (e.g. the Dallol Depression)
    • Grabens, also called troughs
    • Cinder cones and Volcanic mountains
  • Large part of the area is covered by extensive salt plains and lakes (e.g. Lake Assale and Lake Afrera).
  • Bounded by parallel fault lines on the east and west; floor made up of Grabens such as the Tendaho Graben, Volcanic ash and lava deposits, Lacustrian and fluvial deposits, and Volcanic mountains such as Mount Fentalle.
  • Has special characteristics that do not exist in other regions of Ethiopia, including Fossil-rich sediments, rich archeological sites where the ancient ancestors of primates and hominids evolved
b) The Main Ethiopian Rift or the Lakes Region (Central Part)
  • Covers the area from the lower Awash basin up to Lake Chamo; most elevated and narrowest part of the Ethiopian Rift Valley, as well as being the wettest, most densely vegetated, and most densely populated
  • Sedentary farming is practiced, and area includes numerous lakes of enormous economic and aesthetic value.
c) The Chew-Bahir Rift (Southern Part)
  • Also known as the Omo-Gibe trough, is the smallest section of the Ethiopian Rift System separated from the Lakes’ Region to the north by the Konso Highlands and its surroundings
  • Consists of an extensive shallow marshy area covered by tall grasses, into which the Sagan and Woito streams end
  • Split into the Ganjuli and the Galena Valleys by the Amaro mountain range near Arba Minch; largely occupied by a pastoralist population

UNIT TWO: CLIMATE OF ETHIOPIA

Introduction

  • Climate controls the distribution of flora and fauna, largely determining agricultural activities and materials for shelter and clothing.
  • After completing this unit, you will be able to:
    • recognize the meaning and concepts of weather and climate
    • identify elements of climate
    • distinguish elements of climate from its controls
    • compare and contrast the spatial and temporal variations of climate
    • identify factors affecting climate of Ethiopia

Main Contents

  • 2.1 Meaning of Weather and Climate
  • 2.2 Elements of Weather and Climate
  • 2.3 Controls of Weather and Climate in Ethiopia
  • 2.4 Climatic Regions and Seasonal Variations in Ethiopia
  • 2.5 Measurements of Weather and Climate

2.1 Meaning of Weather and Climate

Objectives

  • Recognize the meaning and concepts of weather and climate.
  • Define weather and climate.
  • Describe the difference between weather and climate.
  • Weather and climate are closely related but have different meanings.
  • Weather: condition of the atmosphere (temperature, rainfall, pressure, wind, moisture, cloud cover, humidity, etc.) observed in a certain place over a short period of time. It varies significantly from hour to hour or day to day.
  • Climate: pattern of weather conditions experienced in an area over a long period of time considering trends, fluctuations, and variations in time and space. Large areas experience one type of climate.

2.2 Elements of Weather and Climate

Objectives

  • Identify elements of weather and climate.
  • Define the elements of weather and climate.
  • Differentiate the elements of weather and climate from their controls.

Elements of Weather and Climate:

  • Precipitation: liquid or frozen water that forms in the atmosphere and falls back to the Earth (rain, sleet, hail, snow).
  • Temperature: degree of measurement of hotness or coldness of an object.
  • Humidity: concentration of water vapor present in the air.
  • Air pressure: force exerted on a surface by the air above it as gravity pulls it to Earth.
  • Wind: movement of air caused by uneven heating of Earth and Earth’s rotation.
  • Sunshine: direct sunlight to which a given area is exposed
  • Cloud: visible mass of water droplets or ice crystals suspended in the atmosphereDistribution is uneven, governed by climate control factors.

2.3 Controls of Weather and Climate in Ethiopia

Objectives

  • Distinguish elements of climate from its controls.
  • Spatial and temporal distribution of climatic elements are determined by various physical factors (controls of weather and climate).
  • Most important controls:
    • Latitude
    • Altitude
    • Mountain barriers
    • Revolution of the earth and the inclination of the earth’s axis
    • Distance from the sea
    • Ocean currents

a) Latitude

  • Angular location of a place or point with reference to the direct rays of the sun.
  • Ethiopia’s location within the tropical zone results in;
    • high temperatures during most of the year,
    • high daily (diurnal) ranges of temperature,
    • relatively small annual ranges of temperature, and
    • little difference between summer and winter in the ratios of daylight to night.

b) Altitude

  • The main factor that determines the spatial distribution of temperature in Ethiopia.
  • Temperature decreases as altitude ascends.
  • Example: Three Ethiopian cities, Bako, Addis Ababa, and Awash all lie on the 9oN latitude, and therefore they might be expected to receive equal magnitudes of direct rays from the sun and therefore equal temperatures. However, their altitudes vary, and therefore their temperatures vary, as shown in Table 2.1.

c) Mountain Barriers

  • Influence spatial distribution of rainfall.
  • Leeward side (rain shadow) receives little rain. The side of the mountain facing the wind laden with moisture is called the windward side mountain.

d) Revolution of the Earth and the Inclination of the Earth’s Axis

  • The axis of the earth inclines 23½o to the normal of the elliptic. As the earth revolves around the sun, this inclination produces a change in the angle of the sun