Grade 8 Social Studies Student Textbook Notes

PHYSICAL CHARACTERISTICS OF THE EARTH

Learning Outcomes

Differentiate between internal and external forces shaping the surface of the earth.
Identify landforms formed by the earth’s internal and external forces.
Describe thermal and compositional layers of the atmosphere.
Distinguish between weather and climate.
Identify elements and controls of weather and climate.

1.1 Forces Shaping the Earth’s Surface

Internal or Tectonic Forces: These originate from within the Earth and create reliefs on the crust. They include folding, faulting, volcanism, and earthquakes.
- Folding: The bending of rock layers due to earth movements from one or two sides. Most visible in sedimentary rocks.
  - Monocline: All rock layers bend in the same direction.
  - Anticline: Upward bending of rock layers.
  - Syncline: Downward bending of rock layers.
- Fold Mountains: Formed by crust uplifted and folded by compressional forces. Usually found along continental edges where thick sedimentary deposits accumulate.
  - Major Examples: Andes (South America), Rockies (North America), Alps (Europe), Himalayas (Asia), Atlas (North Africa), Cape Ranges (South Africa), Australian Alps (Australia).
- Faulting: Cracks in the crust caused by tensional force (Normal fault) or compressional force (Reverse fault).
  - Rift Valleys: Formed when land between two parallel faults sinks. The East African Rift Valley is the largest ( $7200\,\text{km}$ from Syria to Mozambique, covering $5600\,\text{km}$ in Africa).
  - Block (Horst) Mountains: Formed by the uplift of land between two parallel faults.
- Volcanism: The process where molten rock (Magma) is forced to the surface; it is called Lava once it reaches the surface.
  - Extrusive Landforms: Volcanoes, craters, calderas (wide craters), and Crater Lakes (e.g., Mount Zequala).
  - Intrusive Landforms: Batholith (large mass), Laccolith (mushroom shape), Dyke (vertical solidification), and Sill (horizontal solidification).
  - Types of Volcanoes:
    1. Active: Recent history of eruption (e.g., Erta'li, Fentale).
    2. Dormant: Not erupted for a long time but may in the future (e.g., Tatali, Dabbahu).
    3. Extinct: Dead volcanoes not expected to erupt (e.g., Mt Ras Dejen, Mt Batu, Mt Zuquala).
- Earthquakes: Sudden movements in the crust taking place along fault lines.
  - Focus: Origin point below the surface.
  - Epicenter: Point on the surface directly above the focus.
  - Measurement: Seismometer/Seismograph records intensity. Magnitude uses the Richter scale ( $0$ to $9$ ).
  - The Ring of Fire: Path along the Pacific Ocean containing $75\%$ of volcanoes and $90\%$ of earthquakes.
External or Gradational Forces: Act from the outside to level the surface through denudation (weathering and erosion) and deposition.
- Weathering: Breaking down rocks into smaller particles.
  - Physical (Mechanical): Main agents are temperature change (Exfoliation or onion skin weathering), frost action (Screes), and plant/animal action.
  - Chemical: Changes rock internal structure. Agents include rain (carbonic acid forming caves with Stalactites, Stalagmites, and Pillars) and plant/animal bacteria.
- Erosion: Movement of particles by water, wind, ice, or waves.
  - Running Water: Sheet erosion (wide flow), Rill erosion (small channels), and Gully erosion (deep wide gorges).
  - Wind: Strongest in deserts. Forms Sand dunes, Barchans (crescent-moon shape), and Loess deposits (fertile soil).

1.2 Composition and Structures of the Earth’s Atmosphere

Atmosphere: Envelope of transparent, colorless, tasteless, and odorless gases.
Composition: Primarily Nitrogen ( $78\%$ ) and Oxygen ( $21\%$ ), with minor gases like Argon and Carbon Dioxide, plus aerosols (dust and moisture).
Structure (Based on Temperature):
- Troposphere: Lower portion ( $8-16\,\text{km}$ ); contains $3/4$ of atmospheric mass. Weather occurs here. Top boundary is the Tropopause.
- Stratosphere: Extends to about $50\,\text{km}$ . Temperature increases due to Ozone absorbing UV radiation. Boundary is the Stratopause.
- Mesosphere: Coldest layer (down to $-100\,^\circ\text{C}$ ), extends to $80-85\,\text{km}$ . Meteorites burn here. Boundary is the Mesopause.
- Thermosphere: Extremely low density; temperatures reach $725-1,225\,^\circ\text{C}$ . Subdivided into:
  - Ionosphere: Electrically charged particles for radio communication.
  - Exosphere: Outermost fringe ( $500-700\,\text{km}$ and beyond); rich in hydrogen and helium.

1.3 Elements and Controls of Weather and Climate

Weather: Atmospheric condition over a short period.
Climate: Average conditions over a long period (minimum $30$ years).
Elements:
- Temperature: Measured by Thermometer. Heat transfer via Radiation, Conduction (solid contact), and Convection (density differences in fluids).
- Rainfall: Measured by Rain gauge. Processes in the hydrological cycle: Evaporation, Transpiration, Evapotranspiration, Condensation, Sublimation (ice to vapor), and Deposition (vapor to ice).
  - Types: Relief/Orographic (mountains), Convectional (sun-heated surfaces), and Frontal/Cyclonic (air masses meeting).
- Air Pressure: Weight exerted by air. Measured by Barometer. Standard sea level pressure is $1,013\,\text{mb}$ ( $760\,\text{mm}$ ).
- Wind: Horizontal movement from high to low pressure. Measured by Anemometer (speed) and Wind Vane (direction).
Controls: Latitude (most important global factor), Altitude (Normal Lapse Rate is $6.4\,^\circ\text{C}$ per $1000\,\text{m}$ ), Distance from the Sea, Cloud Cover, and Ocean Currents.
Ethiopia’s Agro-climatic Zones:
- Wurch/Kur: > 3,300\,\text{m}, < 10\,^\circ\text{C} (Alpine).
- Dega: $2,300–3,300\,\text{m}$ , $10 –15\,^\circ\text{C}$ (Temperate).
- Woina Dega: $1,500–2,300\,\text{m}$ , $15 –20\,^\circ\text{C}$ (Sub-tropical).
- Qolla: $500–1,500\,\text{m}$ , $20 –30\,^\circ\text{C}$ (Tropical).
- Bereha: Below $500\,\text{m}$ , > 30\,^\circ\text{C} (Desert).

PEOPLE AND SOCIOECONOMIC ACTIVITIES

2.1 Cultural Diversity and Changes

Culture: Symbols, language, religion, beliefs, and artifacts of a society.
- Material Culture: Artifacts, tools, houses, technology.
- Non-material (Symbolic) Culture: Values, beliefs, symbols, and language.
Language Families in Ethiopia:
- Semitic: Amharic, Ge’ez, Guragigna, Tigrigna.
- Cushitic: Afarigna, Agewigna, Afan Oromo, Sidamigna, Somaligna.
- Omotic: Welaytta, Gamo-Gofa, Basketto.
- Nilo-Saharan: Agnuak, Berta, Gumuz.
Globalization: Increasing interconnections across nations. Risks include Cultural Imperialism (promoting a powerful nation's culture over indigenous ones) and the loss of local identities via mass media (Satellite TV).

2.2 Major Economic Activities

Primary: Resource extraction (Agriculture, Forestry, Fishery, Mining).
Secondary: Adding value to products (Manufacturing, Construction, Power production).
- Industry refers to the place, while Manufacturing is the activity.
Tertiary: Support services (Transport, Communication, Trade, Tourism, Health, Education).
Development Gap: Developed nations have a large share of manufacturing and tertiary sectors with surplus agricultural production despite fewer workers. Developing nations remain largely agrarian (> 1/4 of national output).

2.3 Trade, Market, and Consumer Rights

Trade: Buying, selling, or exchanging commodities. Oldest form is Bartering.
- Internal (Domestic): Wholesale and Retail.
- External (International): Import, Export, and Entrepot trade (re-exporting imported goods).
Market Forces: Demand (buyers' willingness) and Supply (sellers' willingness). The intersection is Market Equilibrium ( $P = \text{Price}$ , $Q = \text{Quantity}$ ).
Competitive Market: Requires many buyers/sellers (price takers), uniform goods, and freedom to enter/exit.
Consumer Protection: Proclamation No. $685/2010$ in Ethiopia outlines the right to accurate information, selective buying, respectful treatment, and compensation for damages.

2.4 Government Revenue and Tax

Government Revenue: Income from taxes and non-tax sources used for public expenditure.
Taxation: Mandatory fee levied to finance infrastructure and services (e.g., Social Security, roads).
Ethiopian History:
- King Zerayacob ( $1434-1468$ ): Introduced the first tax system.
- Emperor Menelik II: Established a fixed tithe ( $1/10$ ).
- Derg Regime ( $1975-1991$ ): Rural land use fee was Birr $5$ for cooperative members, Birr $10$ for individual peasants, and Birr $2$ per hectare for state farms.
- Transition/Modern: Proclamation $30/1992$ exempted the first Birr $105$ or Birr $120$ from monthly income tax.

NATURAL RESOURCES AND SOCIOECONOMIC DEVELOPMENT

3.1 Conservation and Utilization

Classification:
- Renewable: Can be generated again (sunlight, soil, water, plants).
- Non-renewable: Exhaustible (coal, petroleum, natural gas, iron).
Sustainable Development: Providing for present generations without compromising the future.
Soil Conservation Methods: Terracing, Afforestation, Reforestation, Crop Rotation, Shelter belts (wind protection), Check Dams (silt trapping), Strip cropping, and Contour ploughing.
Case Study: Konso Cultural Landscape: UNESCO site. Stone walled terraces (contoured hills up to $5\,\text{meters}$ high) practicing sustainable agriculture for over $400$ years (millet, sorghum, moringa).
Wildlife Factors: Deforestation, illegal hunting (ivory, skin), overgrazing, and forest burning.

3.3 Resource Accessibility and Conflict

Hydro-politics: The study of inter-state politics regarding shared water resources.
The Nile Basin: Contested by $11$ countries. Upper course countries (e.g., Ethiopia) contribute water but have historically benefited the least compared to lower course countries (Egypt and Sudan). Movement today is toward equitable utilization.

EARLY MODERN AND MODERN WORLD HISTORY

4.1 Great Geographical Discoveries

Pioneers: Portugal and Spain.
Major Discoverers:
- Bartholomew Diaz ( $1487$ ): Reached Southern tip of Africa ("Cape of Good Hope").
- Vasco Da Gama ( $1497-1498$ ): Reached India via the sea route around Africa.
- Christopher Columbus ( $1492$ ): Reached the Bahamas/Americas (thought it was Asia).
- Amerigo Vespucci: Proved the Americas were a "New World."
- Ferdinand Magellan ( $1519-1522$ ): First circumnavigation ( $44,000\,\text{miles}$ ); proved the world is round.

4.2 Renaissance, Reformation, and Counter-reformation

Renaissance: "Rebirth" (approx. $300$ years). Started in Italy. Achievements include Gutenberg's printing press ( $1450$ ), Machiavelli's The Prince, Shakespeare's plays, Da Vinci's Mona Lisa, and Copernicus's Heliocentric theory.
Reformation ( $1517$ ): Started by Martin Luther (Germany) who nailed the Ninety-Five Theses to the church door. Revolted against worldliness, simony (selling offices), nepotism, and the sale of indulgences.
Counter-Reformation: The Catholic response. Council of Trent ( $1545-1563$ ) reaffirmed Papal supremacy; Ignatius Loyola founded the Jesuits.

4.3 Industrial Revolution

Stages:
1. First ( $1750-1870$ ): Steam power, coal, iron, and the first factories in England.
2. Second ( $1870\text{-Present}$ ): Electricity, petroleum, atomic energy, and space vehicles.

4.4 The Two World Wars

WWI ( $1914-1918$ ): Causes: Nationalism, Imperialism, Alliances (Triple Alliance vs. Triple Entente), and Militarism. Trigger: Assassination of Archduke Franz Ferdinand in Sarajevo (July $28, 1914$ ).
WWII ( $1939-1945$ ): Causes: Totalitarianism, Militarism, and Imperialism. Trigger: German invasion of Poland (Sept $1, 1939$ ). Resulted in the establishment of the United Nations and the use of atomic bombs on Hiroshima and Nagasaki ( $1945$ ).

4.5 The Cold War ( $1945-1991$ )

Competition between Capitalist bloc (led by USA) and Communist bloc (led by USSR).
Fought via propaganda, diplomacy, and space/arms races. Notable policies: Truman Doctrine and Marshall Plan. Ended under Soviet leader Mikhail Gorbachev (Glasnost policy).

AFRICA SINCE THE 1500S

5.1 Slavery and the Slave Trade

Triangular Trade:
1. Europe to Africa: Manufactured goods (guns, cloth).
2. Africa to New World: Slaves (Middle Passage; mortality rate $15-30\%$ ).
3. New World to Europe: Plantation crops (sugar, coffee, cotton).
Abolition: British ( $1834$ ), French ( $1848$ ), Cuba ( $1860$ ), USA ( $1865$ ), Brazil ( $1888$ ).
Liberation Settlements: Sierra Leone ( $1787$ ) and Liberia ( $1822$ ) established for freed blacks.

5.2 Colonialism in Africa

Berlin Conference ( $1884-1885$ ): Established principles of "effective occupation."
Administration Styles:
- Direct Rule: French, German, Portuguese (aimed to "assimilate" subjects).
- Indirect Rule: British (used local traditional leaders and laws).
Independence Pioneers: Ghana (Kwame Nkrumah, $1957$ ), Guinea, Kenya (Jomo Kenyatta, $1963$ ).

5.3 OAU and AU

Organization of African Unity (OAU): Founded $1963$ in Addis Ababa. Objectives: promote unity, end colonization and apartheid.
African Union (AU): Launched $2002$ in Durban, South Africa. Vision: Agenda 2063 (integrated, prosperous, and peaceful Africa).

MODERN HISTORY OF ETHIOPIA

6.1 Formation of Modern Empire State

Emperor Tewodros II ( $1855-1868$ ): Defeated regional lords (Battles: Guramba, Gorgora Bichen, Ayshal, Darasge) to end the Era of Princes.
Emperor Yohannes IV ( $1872-1889$ ): Policy of decentralized reunification. Defeated Egyptians (Gundat $1875$ , Gura $1876$ ). Died at Battle of Matamma ( $1889$ ) fighting Mahdists.
Emperor Menelik II ( $1889-1913$ ): Unified the south, east, and west. Key Battles: Azule (Arsi), Chalanqo (Harar), Walayta (Kawo Tona), and Kaffa (Gaki Sherocho).

6.4 Defensive Unity

Battle of Adwa (March $1, 1896$ ): Response to Article XVII of the Treaty of Wuchale. Victory against Italians led by General Baratieri; ensured Ethiopian independence and spurred the Treaty of Addis Ababa.
Fascist Italian Aggression ( $1935-1941$ ): Benito Mussolini's invasion. Key battles in the north (Amba Aradom, Maichew) and south (Qorahe). Ethiopia liberated May $5, 1941$ .
Somalia Invasion ( $1977$ ): Siyad Barre attempted to take Ogaden. Defeated by Ethiopia with Soviet and Cuban assistance at the Battle of Kara Mara.

CONTEMPORARY GLOBAL ISSUES

7.1 Climate Change

Greenhouse Gases: Water vapor, Carbon dioxide ( $CO_2$ ), Methane ( $CH_4$ ), Chlorofluorocarbons (CFCs), and Nitrous Oxide ( $N_2O$ ).
Greenhouse Effect: Natural process where the atmosphere traps heat energy from the sun.
Ozone Layer: Found in the Stratosphere; depleted by CFCs.
Mitigation Strategy (Ethiopia): Climate-Resilience Green Economy (CRGE) strategy aims for middle-income status [low emissions] by $2025$ .

7.2 Water Scarcity and Deforestation

Water Scarcity: Lack of sufficient/safe water; causes food shortages and sanitation diseases (trachoma, plague, typhus).
Deforestation: Indiscriminate cutting of trees for agriculture, urbanization, or fuel. Causes loss of habitat, erosion, and increased greenhouse gases.

QUESTIONS & DISCUSSION

Q: What are the internal forces affecting landform formation?A: Internal forces include folding, faulting, volcanism, and earthquakes.

Q: How is the mean annual temperature obtained?A: By adding the average monthly temperatures and dividing the sum by $12$ .

Q: What is the significance of the Ring of Fire?A: It is the region where $75\%$ of Earth’s volcanoes and $90\%$ of earthquakes occur.

Q: What were the results of the Council of Trent?A: Reaffirmed Papal supremacy, restricted Church abuses like simony and sale of indulgences, and required clergy to renounce worldly pleasures.

Q: How did the youth's clothing change during globalization in Ethiopia?A: The youth have increasingly left traditional Ethiopian styles for foreign/Western fashion trends, which local observers say negatively affects the domestic fashion industry.